Study of thermal conductivity of materials. Study of the thermal conductivity of a solid body using the cylindrical layer method. Interesting facts about thermal conductivity

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Introduction.

Today the question is very acute rational use thermal and energy resources. Ways to save heat and energy are continuously being developed in order to ensure energy security for the development of the economy, both of the country and of each individual family.

The house loses heat through the enclosing structures (walls, windows, roof, foundation), ventilation and sewerage. The main heat losses occur through the enclosing structures - 60-90% of all heat losses.

Calculation of heat loss at home is needed, at a minimum, to select the right boiler. You can also estimate how much money will be spent on heating in the planned house. It is also possible, thanks to calculations, to analyze the financial efficiency of insulation, i.e. to understand whether the costs of installing insulation will be recouped by fuel savings over the service life of the insulation.

The concept of thermal conductivity of materials is studied at school in the 8th grade. Thermal conduction is the process of energy transfer from the warm part of a material to the cold part of the material by particles of this material (i.e. molecules).

We decided to study the thermal conductivity of various substances and materials, and also determine which modern insulation materials are the most effective.

Thus, we have determined the topic of our work.

Subject: Study of thermal conductivity of various substances.

Purpose of the study:

Determine the thermal diffusivity coefficient of various substances, and identify the best heat insulators from modern building insulation materials.

Research methods:

Object of study: Various substances and construction heat insulating materials.

Subject of study: Thermal conductivity of substances.

Hypothesis:

If the temperature of a substance changes slightly over a certain period of time, then this substance has poor thermal conductivity, i.e. retains heat well.

Effective thermal insulators have a low thermal diffusivity.

2. Main part.

IN modern conditions Increases in fuel prices have also changed approaches to thermal protection of buildings, and the requirements for building materials have increased. Any home needs insulation and a heating system. Therefore, when performing thermal engineering calculations of enclosing structures, it is important to calculate the thermal conductivity index.

Thermal conductivity- this is a physical property of a material in which thermal energy inside the body moves from its hottest part to the colder one. The value of the thermal conductivity indicator shows the degree of heat loss in residential premises.

Coefficient of thermal conductivity - is a physical parameter of a substance and in general depends on temperature, pressure and type of substance. In most cases, the thermal conductivity coefficient for various materials is determined experimentally using various methods. Most of them are based on measuring heat flow and temperature changes in the substance under study.

In a school setting, it is difficult to determine the energy passing through a surface. Therefore, in our work we decided to determine not the energy, but the change in temperature per unit time. This coefficient is called the thermal diffusivity coefficient.

Thermal diffusivity coefficient(a) - serves as a measure of the rate at which a porous medium transmits a change in temperature from one point to another per unit time.

To determine the coefficient, we collected easy installation, tripod, holder and thermometer, sample holder, 100 W incandescent lamp as a heating source.

2.1. Study of thermal conductivity of gases.

Target: Determination of the thermal diffusivity coefficient of gases.

As is known, gases are poor conductors of heat. Because of long distance between molecules, energy takes a long time to transfer from molecule to molecule, i.e. the time of temperature change will be long.

Experimental conditions: we took a test tube, heated the air in the test tube from below with an incandescent lamp, and measured the temperature in the test tube with a thermometer. The initial temperature of the thermometer is 20°C.

The temperature around the lamp is 65°C.

Conclusion: Air conducts heat poorly, this is proven by the calculated thermal diffusivity coefficient = 0.8 °C/min.

If we leave small air gaps between the finishing materials of walls, floors, etc., then we reduce energy losses.

2. 2 .Study of thermal conductivity of liquid.

Target: Study of the thermal conductivity of various liquids and determination of their thermal diffusivity coefficient.

Experimental conditions: we poured water, sunflower oil and alcohol into a test tube, heated it from below with an incandescent lamp, and measured the temperature in the test tube with a thermometer.

External factors influencing experimental data: temperature environment.

The initial temperature of the thermometer is 16°C, the temperature around the lamp is 65°C.

Liquids	t-temperature	Change temperature	t- time	temperature coefficient conductivity °C/ min.
				Average 2.6
				Average 3.7
				Average 5.1

Conclusion: Water has the highest heat capacity of these liquids, i.e. expends a lot of energy when heating. This explains the results of the experiment: water heats up slower than oil and alcohol, so its average coefficient of thermal diffusivity is the smallest and is equal to 2.6°C/min, for oil 3.7°C/min, for alcohol 5.1°C/min.

The best heat conductor is alcohol, which has the highest thermal diffusivity coefficient.

Water is the best insulator of heat.

Air and water do not transmit heat well, i.e. This is good thermal protection. We know examples: winter grain under the snow, fur coats, multi-chamber double-glazed windows, etc. But solids are used to insulate houses and apartments.

It is solid substances - insulation - that help keep the house warm.

2.3.1. Determination of thermal diffusivity coefficient various types glass and other materials.

We investigated the thermal conductivity of materials that are most often used in construction.

Name	Temperature change	Coefficient temperature conductivity E=∆ t/ t(°C / min)
			Average value
Plain glass
Plexiglas
Plexiglas (green)
Galvanized iron
Drywall

Conclusion: According to our data, plain glass has the lowest thermal diffusivity coefficient of the three types of glass. It is plain glass that is used in double-glazed windows for the purpose of thermal insulation.

Popular building materials for finishing walls and floors - plasterboard and laminate - have a low thermal diffusivity coefficient of 1.4 °C/min and 1.2 °C/min, so it is no coincidence that they are the leaders in thermal insulation of all solid materials studied.

Galvanized iron has a thermal diffusivity coefficient = 1.0, which means that by covering roofs with this material we can significantly reduce heat loss from the house.

2.3.2. Determination of the thermal diffusivity coefficient of various building materials.

To carry out this research, we went to the Alex-Stroy building materials store. We were kindly provided with samples of modern thermal insulation materials: mineral wool, glass wool, jute fiber, isolon, penoplex and jermaflex.

We decided to determine the best thermal insulator by combining these samples with drywall, which is used to line the walls of rooms. By combining drywall with insulation you can obtain effective thermal protection for your home.

Initial t thermometer=16°C, t near the lamp =65°C.

Name	Temperature change	Coefficient temperature conductivity E=∆ t/ t(°C / min)
			Average value
Drywall
Drywall + mineral wool
Drywall + glass wool
Drywall + jute fabric
Drywall + penoplex
Drywall + isolon
Drywall + jermaflex

Conclusion: From the data in the table it can be seen that building insulation materials significantly reduce the thermal diffusivity coefficient. The lowest thermal diffusivity coefficient of 1.0 °C/min has a combination of plasterboard with mineral wool or penoplex 1.1°C/min. Thus, the most effective thermal protection of room walls will be insulation using mineral wool or penoplex.

2.3.3. Determination of the most profitable heat insulator at a price per 1 sq.m.

Conclusion: The most affordable heat insulator is ...., but taking into account the effectiveness of thermal insulation, it is better to choose ...

3. Conclusion.

Thermal conductivity of various substances - this topic, which we study in grade 8, has important practical applications.

With huge heating prices, every person begins to think about how to keep the house warm.

To assess the level of thermal insulation of materials, we introduced a new value - the thermal diffusivity coefficient, which was calculated by measuring time and temperature with a stopwatch and thermometer.

Having calculated the thermal diffusivity coefficient, we determined that the best heat insulators are air and water. But solid materials are used to insulate houses. Modern production offers a variety of insulation materials. We chose only commonly found thermal insulators in the Alex-Stroy building materials store. Of these, we determined that the best heat insulators are plasterboard and laminate, and even better in combination with mineral wool, isolon or penoplex.

Our hypothesis that the best thermal insulators have a low thermal diffusivity coefficient was confirmed.

Thus, the relevance of the topic of keeping warm in the house has led us to important conclusions that we can use in life. We are convinced that the cost of insulation for building materials pays off in a short time with warmth and comfort in our homes.

4. List of references.

https://ru.wikipedia.org/wiki/

www.rg.ru/ 2010 /12/31/deti-inform-dok.htm

Objective

Mastering and consolidating theoretical material in the heat transfer section “Thermal Conductivity”, mastering the method of experimental determination of the thermal conductivity coefficient; acquiring measurement skills, analyzing the results obtained.

1. Experimentally determine the thermal conductivity coefficient of the insulating material.

2. Write down the table value of the thermal conductivity coefficient of the material under study.

3. Calculate the error of the value of the thermal conductivity coefficient found in the experiment in relation to the tabulated one.

4. Draw a conclusion about the work.

METHODOLOGICAL INSTRUCTIONS

When carrying out technical calculations, it is necessary to have the values of the thermal conductivity coefficients of various materials.

The thermal conductivity coefficient characterizes the ability of a material to conduct heat. Numerical value l hard materials, especially heat insulators, as a rule, is determined empirically.

The physical meaning of the thermal conductivity coefficient is determined from the Fourier equation written for the specific heat flow

g = –l grad t . (1)

There are several methods for experimentally determining the value of l, based on the theory of stationary or non-stationary thermal conditions.

Differential equation heat flow Q, W, with stationary thermal conductivity can be written in the form

Q = – lF grad t . (2)

If we consider a thin-walled cylinder, when l/d > 8, the temperature gradient of the temperature field in the cylindrical coordinate system will be written as

grad t = dt/dr,

and equation (2) of this case

where d 1, d 2 are the inner and lower diameters of the cylinder, respectively, m;

l is the length of the cylinder, m;

(t 2 - t 1) = Dt - temperature difference between the internal and outer surface cylinder, 0 C;

l is the thermal conductivity coefficient of the material from which the cylinder is made, W/(m×0 C);

grad t - temperature gradient normal to the heat exchange surface, 0 C/m.

If equation (3) is solved with respect to the thermal conductivity coefficient l, W/(m× 0 C), then we will have

l = Q ln(d 2 /d 1) / (2plDt). (4)

Equation (4) can be used to experimentally determine the value of the thermal conductivity coefficient of the material from which the cylinder is made.

When conducting an experiment, it is necessary to determine the magnitude of the heat flow Q, W, and the values (t 2 - t 1) = Dt 0 C, upon the onset of a stationary thermal regime.

EXPERIMENTAL SETUP

The experimental setup (Figure) consists of a cylinder 1, in the inner cavity of which an electric heater 2 is placed, its power is regulated by an autotransformer (toggle switch) 3 and is determined by the readings of an ammeter 4 and a voltmeter 5. The temperature of the inner and outer surfaces of the cylinder is measured using Chromel-Copel thermocouples 7 connected to a microprocessor temperature meter 6. Based on the difference between these temperatures in a stationary thermal mode, the thermal conductivity coefficient of the material under study from which the cylinder is made is determined.

Drawing . Scheme of the experimental setup for determining the thermal conductivity coefficient of the cylinder material.

EXPERIMENTAL PROCEDURE

1. Turn on the equipment by turning the knob on the switchboard to position 1.

2. Turn the autotransformer knob (toggle switch) to set the heater power set by the teacher.

3. Observing the temperature meter readings, wait until a stationary thermal regime is established.

4. Present the measurement results in the table:

Table

Experience number	U, V	I, A	t 1.0 C	t 2.0 C

where U, I - voltage and current in the heater;

t 2, t 1 - temperature of the internal and external surfaces of the cylinder.

PROCESSING OF EXPERIMENTAL DATA

1. Calculate the thermal conductivity coefficient of the material under study, l, W/(m× 0 C)

l eq = Q ln (d 2 /d 1) / (2plDt),

where Q = U×I – heater power, W;

d 1 = 0.041 m, d 2 = 0.0565 m – internal and outer diameters cylinder;

l = 0.55 m – length of the cylinder.

2. Write down the table value l, W/(m× 0 C).

3. Determine the error l eq relative to the reference value l, %.

D = (l eq – l)100/l.

QUESTIONS FOR INDEPENDENT PREPARATION

1. Steady and unsteady thermal regimes.

2. Temperature field, stationary and non-stationary, stationary field three-dimensional, two-dimensional and one-dimensional.

3. Temperature gradient.

4. The physical essence of the heat conduction process.

5. Fourier equation, its analysis.

6. Thermal conductivity coefficient, factors influencing the value of the thermal conductivity coefficient.

7. Give numerical values of the thermal conductivity coefficient for some materials.

8. What materials are classified as thermal insulation?

9. Write down the value of the temperature gradient for a one-dimensional temperature field in Cartesian and cylindrical coordinate systems.

10.Write down formulas for determining the heat flow Q, W, of flat and cylindrical single-layer and multilayer walls.

11.Write formulas for determining specific heat fluxes g 1, W/m 2, g 2, W/m for flat and cylindrical single-layer and multi-layer walls.

BIBLIOGRAPHICAL LIST

1. Mikheev M.A., Mikheeva I.M. Fundamentals of heat transfer. - M.: Energy, 1977.

2. Baskakov A.P. and others. Heat engineering. - M.: Energoizdat, 1991.

3. Nashchokin V.B. Technical thermodynamics and heat transfer. - M.: Higher School, 1980.

4. Isachenko V.P., Osipova V.A., Sukomel A.S. Heat transfer. - M.: Energy, 1981.

Ministry of Education of the Republic of Mordovia

Department of Education of the Saransk City District Administration

Municipal educational institution

"Secondary school No. 13"

Research work

physics section

“Study of thermal conductivity of various types of textile materials”

Lipasov Mikhail Pavlovich

Scientific adviser: Physics teacher

Palaeva Nina Pavlovna

Saransk 2015

Table of contents

Introduction.

The climate of Mordovia is moderate continental, characterized by cold frosty winters and moderately hot summers.

Basically, the territory of the republic is under the influence of air masses of temperate latitudes, carried by the prevailing western air currents. The weather is often determined by warm air masses arriving with southern cyclones from the Black, Mediterranean and Caspian Seas. Relatively often, the republic comes under the influence of dry continental air masses brought from the southeast. Cold air masses invade from Scandinavia and the Barents Sea.

The average annual air temperature is +4.1…+4.4 °C. The coldest month is January: the average monthly air temperature ranges from –11.1 to –11.6 °C. The absolute minimum was –42…–47 °C. The warmest month is July. Its average temperature is +18.7…+19.1 °C. The absolute maximum reached +37…+39 °С, in 2010 – +39…+41 °С, at MP MSU – +42 °С.

The beginning, end and duration of the seasons are conditional. They are determined based on the dates of stable transition of the average daily temperature through 0 and +15 °C.

The year is divided into two periods: warm and cold. The warm period of the year is established from the moment the average daily temperature passes through 0 °C to positive values. It begins on March 31 - April 2, ends on November 4-6, its duration is 217-221 days. The cold period of the year begins from the moment of stable transition of the average daily air temperature through 0 °C to negative values. It lasts about 5 months (144–148 days).

In winter, cloudy weather with slight frosts (–10…–15 °C) prevails, but in very cold winters there are periods with severe frosts. In some years, with warm and unstable winters, thaws are observed with an intensity of up to +4...+7 °C. The number of thaw days per month ranges from 3–4 to 7–8. Unfavorable winter phenomena include strong winds and snowstorms, ice and frost formations, and fogs. Average number of days with fog in cold period year ranges from 15 to 25, their average duration is 72–118 hours.

Spring begins at the end of March - beginning of April. Its harbinger is the arrival of rooks; starlings and larks arrive in early April. Bird cherry blossoms in mid-May, and lilac at the end of the month. Spring ends with the transition of the average daily air temperature through +15 °C (May 27–29), the duration of spring is 57–58 days. Unfavorable phenomena in the spring are the return of cold weather and frosts, droughts and dry winds. The latter are celebrated annually. Signs of a dry wind are relative humidity air less than 30% at an air temperature above +25 ° C and a wind of at least 5 m/s.

The period with an average daily air temperature of +15 °C and above is considered to be summer; its duration is 91–96 days, ending on August 28–31. Unfavorable events in summer include heavy downpours, hail, thunderstorms, squalls, drought, and hot winds. Heavy rains erode the top fertile layer of soil, carry away valuable soil material into ravines and rivers, and cause lodging of vegetation. Every month the average number of days with heavy rainfall (more than 10 mm) is 1–2, with dry winds of moderate intensity – 3–8.

Autumn begins on August 29 – September 1 and ends in the first ten days of November. Its duration is 65–69 days. In early September, leaf fall begins for poplar, and by mid-September for birch and maple. The weather regime in autumn is unstable, precipitation is often mixed. Adverse autumn phenomena: early frosts on the soil surface and in the air, fog, ice.

Chapter I .Overview of work

1. Rationale work :

In the 8th grade physics course, the section “Thermal Phenomena” aroused my particular interest. As a result of this work, I wanted to deepen and consolidate my existing knowledge in this section of physics.

This topic I chose because I wanted to understand this physical process in more detail.

2. Relevance work :

3. The purpose of this work: V

Job objectives:

4. Research methods: study of literature on the topic “Thermal conductivity”, selection of fabrics for research, system of experiments, comparison of values, construction of tables and graphs.

5. Equipment:

Measuring cylinders (beakers) 3 pcs;

Experimental material (tissue samples);

Thermometers 3 pcs;

Watch;

Tape measure.

6.Theoretical justifications.

Thermal conductivity is the transfer of heat by structural particles of a substance (molecules, atoms, electrons) during their thermal motion.Thermal conductivity -one of the types of heat transfer from more heated parts of the body to less heated ones, leading to temperature equalization. With thermal conduction, energy transfer in a body occurs as a result of the direct transfer of energy from particles (molecules, atoms, electrons) with higher energy to particles with lower energy.Such heat exchange can occur in any body with a non-uniform temperature distribution, but the mechanism of heat transfer will depend on the state of aggregation of the substance. The phenomenon of thermal conductivity is that kinetic energy atoms and molecules, which determines the temperature of the body, is transferred to another body during their interaction or is transferred from more heated areas of the body to less heated areas.

Sometimes thermal conductivity is also called a quantitative assessment of the ability of a particular substance to conduct heat.

Historically, transfer was thought to involve the flow of caloric from one body to another. However, later experiments, in particular, the heating of cannon barrels during drilling, refuted the reality of the existence of caloric as an independent type of matter. Accordingly, it is currently believed that the phenomenon of thermal conductivity is due to the desire to occupy a state closer to thermodynamic equilibrium, which is expressed in temperature equalization.

The thermal conductivity coefficient is the amount of heat passing per unit time through 1 m3 of material when the temperature difference on its opposite surfaces is equal to 1 degree.

The lower the thermal conductivity coefficient, the better the thermal insulation properties of the material.

There are heat-insulating and heat-conducting materials.

7. Characteristics of the studied types of fabrics.

Fabrics with different purposes have different physical properties and characteristics: strength, resistance to crumpling, ability to resist abrasion (on various objects, on the human body), shrinkage, tenacity, breathability, vapor permeability, water resistance, heat resistance. Very important properties of household fabrics are thermal conductivity, i.e. the ability of a fabric to transmit heat. Fabrics designed to protect against cold must have minimal thermal conductivity. For example, high heat resistance and water resistance are important for technical fabrics used to make firefighter clothing.

The basis of all materials and fabrics is fiber. Fibers differ from each other in chemical composition, structure and properties. The existing classification of textile fibers is based on two main characteristics - the method of their production (origin) and chemical composition, since it is they who determine the basic physical, mechanical and chemical properties of not only the fibers themselves, but also the products obtained from them.

Thermal properties are the most important hygienic properties of products for the winter period. These properties depend on the thermal conductivity of the fibers forming the fabric, on the density, thickness and type of finishing of the fabric. Flax is considered the “coldest” fiber, as it has high thermal conductivity, while the “warmest” is wool. Thick, dense brushed wool fabrics have the highest heat-protective properties. The heat-protective properties of clothing are significantly influenced by the number of layers of material in clothing. As the number of layers of material increases, the total thermal resistance increases. Various types of insulation are used: natural andsynthetic.

Let's consider four types of fabrics, samples of which we will study.

Suit fabrics – from natural fibers – wool.

Wool is the hair of sheep, goats, camels and other animals. The bulk of wool (94-96%) for textile industry enterprises is supplied by sheep farming.

A special feature of wool is its ability to felt, which is explained by the presence of a scaly layer on its surface, significant crimp and softness of the fibers. Thanks to this property, wool is used to produce quite dense fabrics, cloth, draperies, felt, as well as felt and felted products. Wool has low thermal conductivity, which makes it indispensable for the production of coat, suit and dress fabrics and winter knitwear.

Natural insulation materials

Wat And n - half-wool insulation,knitted fabric with one-sided or double-sided fleece. Batting is available in cotton, wool, and half-woolen and replaces cotton wool when sewing warm clothes.

In the mid-to-late last century, it was used in the Soviet clothing industry for sewing workwear, and also as insulation for winter coats.

Batting varies in composition (cotton, wool), thickness of the fabric, and method of fastening the dies.

Batting is becoming less and less popular these days.

Disadvantages: heavy weight and relatively high moisture-retaining properties.

Synthetic insulation

Sintepon - is one of the most common synthetic insulation materials. Lightweight, voluminous, elastic, in which a mixture (including secondary artificial and natural textile waste) is held together using a needle-punched, adhesive (emulsion) or thermal method.

Sintepon in Lately most often made from recycled polyester raw materials (recycled PET), melted plastic waste (PET bottles, bags, disposable tableware, etc.). This significantly reduces the cost of the product, but critically reduces the quality and performance characteristics.

Sintepon- non-woven material, obtained from synthetic fibers. It is much lighter than batting, elastic, does not lose shape and does not fall off. Sintepon is not hygroscopic, so it does not get very wet and dries easily. In addition, it comes in white color and when washing insulated items it does not fade or leave stains on the outer fabric. After washing, the product retains its shape and does not lose volume.

The advantages of synthetic winterizer are lightness, good heat-protective properties and low weight, as well as relative harmlessness to humans. Synthetic winterizer is used for all types of insulated clothing, including children's, as well as for the manufacture , bedspreads, and bags and other products.Light, warm, voluminous, cheap - at one time such insulation was at the peak of popularity.

However, as time has shown, synthetic winterizer has a number of disadvantages: increased moisture permeability, air tightness, rapid deformation and fragility of the material - all this has led to the fact that synthetic winterizer is used as insulation for the production of cheaper demi-season and winter clothing.

Hollowfiber (hollow fiber) - non-woven fabric filled with synthetic fibers in the form of spirals, balls, springs, etc. It is this structure that makes the item warm, since a lot of air is retained between the fibers.

It is rightfully considered the insulation of the 21st century. Lightweight, warm, moisture- and shape-resistant, hypoallergenic - it is an excellent material for the production of excellent insulation for winter clothing.

Varieties - polyfiber, thermofiber, fiberskin, fibertek, etc.

Chapter II . Experimental research work

Work progress:

During the implementation of this research work Six experiments were carried out with different types of fabrics. All samples have the same dimensions: length, width and area (photo 1). The area of the samples coincides with the surface area of the measuring cylinder (Table No. 1)

photo 1

Table No. 1

Drape

Suitwool fabric 1

Suitwool fabric 2

Holofiber

Sintepon (thin)

Sintepon (thick)

Batting

Thickness

0.4 cm

0.1cm

0.1 cm

2cm

1 cm

2 cm

0.5 cm

Width

12 cm

Length

13 cm

Square

156 cm 2

2.1 Comparison of thermal conductivity of various textile materials.

Equipment: Measuring cylinders with warm water, experimental materials, mercury thermometers - 3 pieces, electronic thermometer, calipers.

To perform the experiment, we wrapped the measuring cylinders with tissue samples and secured them with pins.

A pair of wrapped cylinders and one unwrapped one chosen for the experiment were filled with warm water of the same temperature. At regular intervals (5 minutes), the temperature of the water in each vessel was measured (photo 2), the readings were recorded in a table, and graphs were drawn for comparison.

photo 2

2.1.1. Experiment No. 1.

For the first experiment we chose two types of wool fabric.

Types of fabrics studied:

The first sample is thin suiting fabric, which is used for sewing jackets, trousers, and skirts.

The second sample is thicker woolen fabric (drape), which is used for sewing coats and jackets.

Fabrics have different thicknesses.

Room temperature (physics room 20ºС)

The results of the study will be entered into the table

9:35

9:40

9:45

9:50

For comparison, let's build graphs

Having compared the water temperature of three beakers and plotted graphs, we saw that the first sample does not retain heat well, therefore it has good thermal conductivity. The thermal conductivity of the second sample (thick woolen fabric) is worse, since it retains heat better.

2.1.2. Experiment No. 2

In the second experiment we examined insulation materials. Synthetic winterizer is now often used as clothing insulation. Thick synthetic winterizer retains heat well.

Length-13 cm

Width-12cm

Thickness-2cm

Area: 156 cm

10:05

10:10

10:15

10:20

Let's build a graph

2.1.3. Experiment No. 3

The second sample is black batting - natural cotton material, knitted fabric with one-sided brushing.

We will put the results in the table

11:05

11:10

11:15

11:20

Let's build a graph

As a result of the experiment, it turned out that the thermal conductivity of padding polyester is worse than that of batting.

2.1.4. Experiment No. 4

To study the thermal conductivity of insulation, we chose the first sample -gray batting (cotton). The second sample is black batting (wool).

Parameters of the objects under study

Gray batting

Batting black

Thickness

0.6 cm

0.5cm

Width

12 cm

Length

13 cm

Square

156 cm 2

13:50

39,5

38,5

13:55

14:00

36,5

14:05

35,3

34,5

14:10

33,1

Let's build a graph

The thermal conductivity of batting is almost the same, but we must take into account that gray batting is thicker.

2.1.5. Experiment No. 5

We studied the thermal conductivity of padding polyester of different thicknesses.

Parameters of the objects under study

Thin padding polyester

Thick padding polyester

Thickness

1 cm

2 cm

Width

12 cm

Length

13 cm

Square

156 cm 2

14:31

31,9

31,7

14:36

30,5

14:41

29,7

29,3

14:46

29,5

28,7

Let's build a graph

The graph shows that the thermal conductivity of thick padding polyester is much less than that of thin padding polyester..

2.1.6. Experiment No. 6

For the study, we chose the first sample - thick padding polyester (synthetic material, light, voluminous, elastic, non-woven material)

Second sample- Xolofiber(non-woven fabric filled with synthetic fibers in the form of spirals, balls, springs).

We will put the results in the table

15:05

15:10

15:15

15:20

Let's build a graph

As a result of the experiment, it turned out that the thermal conductivity of holofiber is worse than that of padding polyester.

Thus, we were convinced that in the conditions of a school physics laboratory it is possible to produce comparative analysis textile fabrics.

2.2Calculation of the thermal insulation coefficient of batting, padding polyester and hollafiber.

According to the formula: the thermal conductivity coefficient is calculated, where

P is the total heat loss power, S is the cross-sectional area of the parallelepiped, ΔT is the temperature difference between the faces, h is the length of the parallelepiped, that is, the distance between the faces.

The thermal conductivity coefficient is measured in W/(m K).

By analogy with the thermal conductivity coefficient, we calculatedthermal insulation coefficient. In our experiment

P=Q1 – Q2/t, power retained by the material. Where: Q1 is the amount of heat given off by water in a graduated cylinder without “clothes” during time t;

Q2 is the amount of heat given off by water in a graduated cylinder with “clothes” during time t;

S is the area of the tissue sample;

h - distance between faces.

2.2.1. Calculation of the thermal insulation coefficient of black batting.

S=88 cm; h=0.5 cm;ΔT=22.2°С-21.2°С=1°С

Q2=4200*0.12*(38.5-37) =756(J),

c = (Q1-Q2)*h/t*SΔT

c=(1008 -756)*0.005/(300*0.0088*1)=1.26/2.64=0.48(W/m*K)

2.2.2. Calculation of the thermal insulation coefficient of light batting.

S=88 cm2; h=0.6 cm;ΔT=24.3°С-22.5°С=1.8°C

Q1=cmΔt=4200*0.12*(38-36) =1008(J)

Q2=4200*0.12*(39.5-38) =756(J)

c= (Q1-Q2)*h/t*SΔT

c= (1008 -756)*0.006/ (300*0.0088*1.8) =1.512/4.752=0.32 (W/m*K)

Conclusion:thermal insulation coefficient of black batting 0.48(W/m*K)

0.32(W/m*K)

2.2.3. Calculation of the thermal insulation coefficient of thin padding polyester.

S=156 cm2; h=0.4 cm; ΔT=23.8°С-22.5°С=1.3°C

Q2=4200*0.12*(29.3-28.7) =307.2(J)

c=(Q1-Q2)*h/t*SΔT

c=(512-307.2)*0.004/(300*0.0273*1.3)=0.82/10.647=0.077(W/m*K)

2.2.4. Calculation of the thermal insulation coefficient of thick padding polyester.

S=156 cm2; h=1.3 cm; ΔT=23.2°С-22°С=1.2°C

Q1=cmΔt=4200*0.12*(28-27) =512(J)

Q2=4200*0.12*(29.7-29.5) =102.4(J)

c=(Q1-Q2)*h/t*SΔT

c=(512-102.4)*0.013/(300*0.0273*1.2)=5.32/9.83=0.54(W/m*K)

thermal insulation coefficient of thin padding polyester 0.077(W/m*K)

thermal insulation coefficient of light batting 0.54(W/m*K)

2.2.5. Calculation of the thermal insulation coefficient of hollafiber.

S=156 cm2; h=2 cm; ΔT=23.8°С-22.5°С=1.3°C

Q1=cmΔt=4200*0.12*(55-52) =1512(J)

Q2=4200*0.12*(61-60) =504 (J)

c=(Q1-Q2)*h/t*SΔT

c=(1512-504)*0.02/(300*0.0156*1.3)=0.82/840=0.024(W/m*K)

Thus, in a school laboratory, it is possible to carry out a comparative analysis of the thermal conductivity of various textile fabrics and experimentally determine the thermal insulation coefficient.

The modern textile industry is increasingly using synthetic fibers. For this purpose, just like in many industries modern production Nanotechnology is coming to the textile industry.

Nanomaterials can contain nanoparticles, nanofibers and other additives. For example, the company Nano-Tex successfully produces fabrics enhanced with nanotechnology. One of these fabrics provides absolutewaterproof: due to a change in the molecular structure of the fibers, drops of water completely roll off the fabric, which at the same time “breathes”. In March 2004, AspenAerogels began production of insulated shoe insoles from a new nanomaterial. The new insulator retains heat better than all existing ones modern materials. Compared to them, its thermal characteristics with the same sample thickness improved from 3 to 20 times. It is not surprising that with such indicators, products made from the new heat insulator have minimal material consumption.

Nanocoatings allowthe integration of micro- and nanoelectronics, as well as MEMS, into textiles significantly expands the capabilities of everyday clothing, which can be used as a means of communication and even a personal computer. And the production of textiles with built-in sensors will allow monitoring the condition of the human body. This will certainly open up new opportunities in medical practice, sports and life support in extreme conditions.

To protect humans from hypothermia, currently developedthermal underwear. Thermal underwear is special underwear, tightly fitting to the body of a special cut. One of the main advantages is that it practically does not stretch. No side seams or just a few flat seams eliminate the risk of chafing.Heat-saving thermal underwear. In other words, warming thermal underwear is intended for low and medium levels physical activity at cool, cold or very cold ambient temperatures. Recommended for use in any weather, if heat retention is necessary, i.e. when you need to warm up, depending on the individual tolerance of the human body.

Moisture-wicking (functional) thermal underwear. This thermal underwear has the ability to remove excess moisture (sweat) from the surface of the skin. As a rule, this type of thermal underwear is made from 100% synthetics. Usage special types synthetics improves the moisture removal properties of thermal underwear. It makes no sense to list all types of synthetics that have such properties. Let's name only the most famous of them: Coolmax, QuickDry, ThermoliteBase, Polypropylene, Viloft, and many, many others.

Heat-saving + moisture-wicking thermal underwear (hybrid).Thermal underwear combining the two above properties, i.e. both warming and moisture-wicking.

Moisture-wicking functional thermal underwear

Heat-saving thermal underwear

Hybrid thermal underwear

Thermal underwear copes with many types of functions- warm, remove moisture, or both at once. Thermal underwear allows you to engage in your favorite active sports in different climatic conditions without creating a feeling of discomfort, and also saves your heat energy.

The thermal conductivity of textile fabrics plays an important role in human clothing, and especially in our climate. Therefore, we want to give some recommendations for choosing clothes:

1) always dress appropriately for the weather.

2) use the layering principle: “three thin T-shirts are better than one thick one.”

3) giving preference to clothes made from natural fibers, remember that science does not stand still and artificial fibers are not inferior, and sometimes surpass natural fibers in their thermal conductivity qualities.

Chapter III Conclusion and conclusions

We examined only a few types of fabrics, natural and synthetic. Modern industry more often uses fabrics made from synthetic fibers. These fabrics have both advantages and disadvantages. The advantage of such fabrics is their poor thermal conductivity, therefore, they retain our heat well.Synthetic winterizer has average thermal insulation properties. Outerwear with padding polyester is only suitable for very mild winter. For harsh climates, synthetic winterizer is unacceptable. But holofiber has excellent thermal insulation (close to natural down) and is well suited for cold weather. Reliably retaining heat, it allows the skin to breathe. Sintepon is less breathable.

Conclusion:

holofiber,holofiber,

Practical significance

List literature

Galakhova E. N.Climate of Mordoviaand associated areas of the Non-Black Earth Region in weather (based on research materials in the Mordovian Autonomous Soviet Socialist Republic): Author's abstract. dis. ...candidate.../

Great Soviet Encyclopedia, volume 43. page 473 .-M.: TSB. 1954

Smorodinsky A.Ya. Temperature. Library "Quantum". Issue 12-M.: “Science”, the main editorial office of physical and mathematical literature, 1981 - 159 p.

Encyclopedia for children "AVANTA". Physics.t.16.ch.2.-M.: “Avanta + ", 2002 - 432 p.

Abstracts

Study of thermal conductivity of various types of textile materials"

Municipal educational institution "Secondary school No. 13", Saransk

Section: physics

Head: N.P. Palaeva, physics teacher.

We live in a temperate continental climate, which is characterized by cold frosty winters and moderately hot summers.

At the end of 2009, the debate about on Earth flared up. There were many scientific facts given that the climate on Earth is becoming warmer and our civilization is to blame. There were also opinions that the theory “ global warming" is wrong. Nature also decided to have its say in the winter frosts. Many European countries were covered with snow, and residents of these countries urgently replenished their wardrobes with warm clothes.

In conditions of predominance different temperatures The problem arises of appropriate clothing, which, if not warm, then retains heat well. Clothing should have low thermal conductivity. And so we decided to study some types of fabrics for thermal conductivity.

The purpose of this work : investigate the thermal conductivity of textile materialsVin a school physics classroom.

Job objectives: study theoretical basis concept of thermal conductivity; experimentally study the thermal conductivity of textile materials; experimentally determine the thermal insulation coefficient of textile materials,compare experimental and tabulated values of thermal conductivity of materials, draw a conclusion.

The main indicator of the thermal insulation properties of a material is the thermal conductivity coefficient.

Relevance of the work:

Possibility of obtaining new thermal insulation materials with better properties.

Thermal insulation plays one of the most important roles in addressing health issues.

In temperate climates, the problem arises of appropriate clothing, which must retain heat well; for this it must have low thermal conductivity.

The use of various types of insulation when sewing clothes can reduce the growth of the disease in the case of thermoregulation of the body.

Such research allows us to radically deepen our understanding of the thermal conductivity of textile materials and find out which material is most effective.

Object of study: In the course of this research work, experiments were carried out with various types of fabrics and insulation materials.Based on the results of the work, the mainconclusions . Having studied the literature on the research topic and compared the experimentally obtained results with tabulated values, it allows us to judge the small measurement error.Thus, we were convinced that in the conditions of a school physics classroom it is possible to conduct a comparative analysis of the thermal conductivity of fabrics that are used to make our clothes.In the process of conducting experiments, I studied the thermal conductivity of two types of suit fabrics (fine and drape) and insulationholofiber,padding polyester and batting. As a result of the experiments, I was convinced that the lowest thermal conductivity hasholofiber,padding polyester, then batting, drape, and thin suiting wool fabric has the greatest thermal conductivity. That is, outerwear made from drape and insulated with hollafiber and padding polyester will retain our warmth well, and, therefore, protect us from the winter cold.

The results obtained during the research show what unique thermal insulation capabilities modern textile materials have and lead to the conclusion about the need to inform and even promote new textile materials among the population. The modern textile industry is increasingly using synthetic fibers. For this purpose, just like in many branches of modern production, nanotechnologies are coming to the textile industry.

Textiles based on nanomaterials acquire unique water resistance, dirt repellency, thermal conductivity, the ability to conduct electricity and other properties.

Practical significance

The thermal conductivity of fabrics plays an important role in human clothing, and therefore in his life. A person should always dress appropriately for the weather to maintain his physical health.

The article presents the results of a study of the heat-shielding properties of continuous warp pile fabric using a thermal imaging installation. As a heat insulator, it is proposed to use a structural material that has the necessary properties - continuous double-panel warp-pile fabric, using cotton and nylon threads in the weft. As a result of the research carried out using a thermal imaging installation based on the TermaCamTM SC 3000 infrared camera, the main thermophysical characteristics of the fabric were determined, thermograms of the cooling process of fabric samples were obtained and, based on the measurement results, semi-logarithmic graphs of their cooling were constructed. As a result of the analysis of experimental data, it follows that the thermal resistance of samples of continuous double-panel warp pile fabric depends on their thickness. As the thickness of a given fabric increases, its thermal resistance increases, that is, the heat-shielding properties improve, regardless of the fiber composition of the fabric in the weft.

warp fabric

heat insulator

thermal imager

thermal resistance

1. Boyko S.Yu. Development of optimal technological parameters for tissue production to protect humans from external influences: Abstract of thesis. dis. Ph.D. tech. Sci. – M., 2004. – 16 p.

2. Vavilov V.P., Klimov A.G. Thermal imagers and their applications. – M.: “Intel Universal”, 2002 – 88 p.

3. Kolesnikov P.A. Basics of designing thermal protective clothing. L.: “Light Industry”, 1971. – 112 p.

4. Nazarova M.V., Boyko S.Yu. Development of a method for designing fabric to protect humans from external influences // International Journal of Experimental Education. – 2010. – No. 6. – P. 75-79.

5. Nazarova M.V., Boyko S.Yu., Zavyalov A.A. Development of optimal technological parameters for the production of fabric with high strength properties // International Journal of Experimental Education. – 2013. – No. 10 (part 2). – pp. 385-390.

6. Nazarova M.V., Boyko S.Yu., Romanov V.Yu. Development of optimal technological parameters for the production of fabric with heat-protective properties // International Journal of Experimental Education. – 2013. – No. 10 (part 2). – pp. 391-396.

Designing rational thermal protective clothing for various climatic and production conditions is a large and very complex scientific problem, which can be successfully solved only on the basis of the integrated use of data from physiology, clothing hygiene, climatology, thermophysics, textile materials science and clothing design.

The thermal conductivity of textile fabrics is associated with the transfer of energy of thermal movement of microparticles from more heated parts of the body to less heated ones, leading to equalization of temperature and is assessed by the coefficient of thermal conductivity; heat transfer coefficient; thermal resistance, specific thermal resistance.

An analysis of works on the study of the thermophysical properties of a material showed that when assessing the heat-protective properties of clothing materials, a simpler and more intuitive value should be considered not the thermal conductivity coefficient, but its inverse value, called thermal resistance. Factors that influence the thermal resistance of a material include: volumetric weight, thickness, humidity, type of fibrous material, air permeability.

Therefore, the purpose of this work is to assess the value of the thermophysical characteristics of warp-pile fabric intended for sewing workwear used in extreme climatic conditions.

In this work, when studying the thermophysical properties of continuous warp pile fabric, it is proposed to use the principle of thermal diagnostics, which consists of comparing the reference and analyzed temperature fields in the fabric under study. Temperature anomalies serve as indicators of defects, and the magnitude temperature signals and their behavior over time form the basis for quantitative assessments of certain tissue parameters.

The term “thermal imaging” refers mainly to the registration of thermal radiation from solid bodies, which consists of the body’s own radiation, due to its temperature, as well as reflected and transmitted radiation from other bodies. For optically opaque objects, thermal imaging devices record exclusively surface effects: surface temperature and the magnitude of emissivity (absorption) and reflection coefficients.

When studying objects using thermal imagers, the two most common wavelength ranges are often used: 3-5.5 µm and 8-12 µm; and they are usually designated as shortwave and longwave bands.

General scheme for measuring thermal radiation of an arbitrary solid shown in Fig. 1. The control object (1) is surrounded by the environment (2) and other objects (3), respectively, with temperatures Tav and Text. A thermal imager (4) is used to record thermal radiation. The test object is characterized by the following optical parameters: emissivity ε; absorption coefficient α; reflection coefficient r; transmittance τ.

Rice. 1. Schematic diagram measurements of thermal radiation of an arbitrary solid body

The main advantage of a thermal imager over other devices when studying the heat-protective properties of materials is:

high thermal sensitivity;
more exact values temperatures;
high speed of obtaining experimental results and their processing;
unlimited temperature range.

When determining the thermophysical characteristics of continuous double-layer warp-pile fabric using a thermal imaging system, a technique developed at the Department of Industrial Thermal Power Engineering of Moscow State Technical University was used. A.N. Kosygina. The method for determining thermophysical characteristics is based on non-stationary thermal regime methods for experimental assessment of the heat-protective properties of clothing materials using the regular thermal regime method, based on the phenomenon of free cooling of a heated sample in a gaseous medium (air).

Studies of the thermophysical characteristics of continuous double-layer warp-pile fabric using a thermal imaging system were carried out in the laboratory of the Department of Industrial Heat and Power Engineering at MSTU. A.N. Kosygina.

When using the thermal imaging system, the following tasks were set:

determination of temperature fields on the surface of the tissue samples under study during cooling;
determination of the thermal conductivity of continuous double-layer warp pile fabric.

The laboratory setup for the experiment is shown in Fig. 2.

Rice. 2. Thermal imaging system for studying the thermal conductivity of base pile fabric: 1 - thermal imaging camera termocamtmsc 3000; 2 - computer for data processing; 3 - thermally insulated cabinet; 4 - protective screen; 5 - thermometer, to control the temperature inside the cabinet; 6 - fabric sample

As is known from the research of A.P. Kolesnikov, the thermal insulation ability of a fabric depends on its thickness. Thickness is of greatest importance in the thermal insulation properties of the fabric. To conduct the experiment, samples of uncut warp-pile fabric with cotton yarn in the warp and pile warps were used. The weft used cotton yarn with a linear density of 15.4 * 2 tex (I-option) and nylon thread T = 15.6 tex (II-option). In each of the options, the thickness of the fabric changed. To carry out the experiment, fabric samples of various thicknesses were used: I - a variant sample with cotton yarn in the weft, and II - a variant sample with nylon thread in the weft. The thickness of the fabric samples in both versions was b1=7.57 mm, b2=7.62 mm.

The algorithm for studying the heat-shielding properties of continuous double-panel warp pile fabric is as follows:

Heating the sample in a heat-insulated cabinet to a fixed temperature t=100 °C (lower than the fiber deformation temperature);

Control of uniform heating of the test sample using the ThermaCAM SC 3000 infrared camera;

When a uniform temperature field is reached on the surface of the sample, turn off the power to the electric heater;

Using the ThermaCAM SC 3000 infrared camera, recording the cooling of the sample to the initial temperature room temperature subject to the conditions , ;

Replacing the test sample (option 1) with another sample (option 2) and performing the entire set of measurements again;

After receiving thermograms of the sample cooling process, the experimental data is processed using a computer;

Using known formulas, we determine the thermal conductivity and thermal resistance of samples of continuous double-panel warp pile fabric.

Experiment conditions:

emissivity of the object (degree of emissivity) - 0.95;
ambient temperature - 23 °C;
distance between the object and the thermal imager - 30 cm;
relative air humidity - 55%.

Using a thermal imaging system, thermograms of the cooling process of a tissue sample are recorded at a frequency of 1 frame per second.

Based on the measurement data, a semi-logarithmic cooling graph was constructed, shown in Figs. 3 and 4; the straight section of the curve corresponds to the regular mode. The equation of this line, according to the basic law of the regular mode (of the first kind), has the following form:

ln υ=-m·τ+g(x,z,z), (1)

Six points with corresponding coordinates are marked on the straight line, according to which the cooling rate is determined.

The cooling rate in each section is determined by formulas (2), s -1:

where υ 1 is the difference between the temperature at a given point and at external environment at time τ 1; υ 2 - the difference between the temperature at a given point and in the external environment at time τ 2;

The average cooling rate is determined by the formula3, s -1:

, (3)

We determine the shape factor for fabric samples using formula (4):

If we assume that the tissue sample conventionally takes the shape of a parallelepiped, then for rectangular parallelepiped with ribs L 1, L 2, L 3, mm:

, (4)

where L 1 is the width of the sample, mm; L 2 - sample length, mm; L 3 - sample height equal to b 1, b 2, mm.

The thermal diffusivity coefficient is determined by formula (5), m2/s:

The bulk density of the samples is determined by formula (6), kg/m3:

where M is the surface density of the sample, g/m2; b - sample thickness, mm.

Rice. 3. Experimental cooling rate curve for a sample of warp pile fabric with cotton yarn in the weft (I-variant)

Rice. 4. Experimental curve of the cooling rate of warp-pile fabric with nylon thread in the weft (II-variant)

The specific heat capacity of the samples is taken from experimental data determined by P.A Kolesnikov:

for option I (cotton) c1=1.38 kJ/kg deg;
for option II (cotton-nylon) with 2 = 1.66 kJ/kg deg;

The thermal conductivity of the material is determined by formula (7), W/m⋅deg:

The thermal resistance of fabric samples is determined by formula (7), m2 deg/W:

where δ is the layer thickness, m; λ - thermal conductivity coefficient, W/m deg.

Calculation of the thermal resistance parameters of samples of continuous double-panel warp pile fabric of two options was carried out on a computer and presented in Table. 2.

table 2

Results of calculating the parameters of thermal resistance of samples of continuous double-panel warp pile fabric

Sample No.	I - option	II - option
Sample No.			Thermal resistance, m2 deg/W

As a result of the analysis of the table data, it follows that the thermal resistance of samples of continuous double-panel warp pile fabric depends on their thickness. As the thickness of a given fabric increases, its thermal resistance increases, that is, the heat-shielding properties improve, regardless of the fiber composition of the fabric in the weft.

The best heat-shielding properties have: - a fabric sample containing cotton yarn in the weft and thickness bT=7.62 mm; a sample of fabric containing nylon thread in the weft and thickness bT = 7.57.

Table 3

Thermophysical characteristics of base pile fabric samples

conclusions

Using a thermal imaging installation based on the TermaCamTM SC 3000 infrared camera, a study of the heat-protective properties of the fabric was carried out, its main thermophysical characteristics were determined, thermograms of the cooling process of fabric samples were obtained and, based on the measurement results, semi-logarithmic graphs of their cooling were constructed.
An algorithm has been developed for calculating the heat-shielding properties of continuous double-panel warp-pile fabric, on the basis of which the main thermophysical characteristics of the fabric are determined.

Bibliographic link

Khairullin A, Salimov I

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RESEARCH OF THERMAL CONDUCTIVITY OF BUILDING MATERIALS AND THEIR FIRE RESISTANCE

Research

Introduction………………………………………………………………………………………...3
Theoretical part………………………………………………………....3-12

2.1 Physical properties of materials…………………………………….3-5

2.2 The concept of thermal conductivity and thermal insulation………………………..6-7

Heat transfer in construction…………………………………………..8-9

2.4 Classification of thermal insulation materials………………………10-11

2.5 Thermal insulation properties of materials…………………………….11-12

3. Practical part. Materials and research methods…………..12-13

4. Fire resistance of materials………………………………………………....14

5. Conclusion and conclusions………………………………………………………..15

6. Literature…………………………………………………………………………………..15

Relevance of the work:is caused by an urgent need to study the properties of building materials and study their fire resistance.

Problem:

How to make your home warm, environmentally friendly and fireproof?

Purpose This work is to study the thermal conductivity of natural and artificial building materials and their fire resistance.

To achieve this goal, the following tasks were identified:

Study the literature on the topic of thermal conductivity and thermal insulation.
Master the research methodology for determining the thermal conductivity of materials.
Give a quantitative assessment of the conductive properties of the samples as the ratio of the temperature change to the time during which this change occurred.
Compare experimental and tabulated values of thermal conductivity of materials.

6. Explore fire safety building materials.

1. Introduction

In cold, rainy, windy weather, we always strive to return to a warm home, where we can take off our coat and feel warm and comfortable. External walls, windows, roof protect our home from low temperatures, strong wind, precipitation in the form of rain and snow and others atmospheric influences. At the same time, they prevent the penetration of heat from the interior to the outside due to their resistance to heat transfer.

What to build a house from? Its walls must provide a healthy microclimate without excess moisture, mold, or cold. This depends on their physical and mechanical properties.

During the 20th century, the world produced as many materials as in the entire previous millennium. Scientific research has made it possible to significantly improve the optical, chemical, thermal and other properties of already known materials and to create thousands of new ones that nature did not know.

The construction boom in Russia of the 21st century has generated demand for heat-insulating materials and structures. In addition, with the beginning of 2000, new requirements for thermal protection of enclosing structures came into force. Insulating buildings with modern building materials can significantly reduce heat loss. Of course, it is best to build from materials that have low thermal conductivity.

2. Theoretical part.

2.1 Physical properties of materials.

Density - a quantity measured by the ratio of the mass of a substance to the occupied volume.

Humidity - mass fraction of water in the material, expressed as a percentage.

To determine moisture content, the sample is weighed first in a wet state and then in a completely dry state. Dry the material until moisture is completely removed in laboratory conditions (in drying cabinet) at a temperature of 110°C. A material whose humidity is 0 is called absolutely dry; if it is equal to the humidity of the surrounding air, it is called air-dry.

Water permeabilityi.e. the ability of a material to pass water under pressure, measured by the amount of water passing through 1 cm 2 surface area of the material for 1 hour at constant pressure. Particularly dense materials (bitumen, glass, steel, etc.), as well as fairly dense materials with small pores (special concrete) are practically waterproof, the rest are water permeable.

Frost resistance- the ability of a material in a water-saturated state to withstand repeated and “alternating freezing and thawing. A material” is considered frost-resistant if, after testing, it does not have chipping, cracks, delamination, weight loss of more than 5% and strength of more than 25%.

Thermal conductivity- the ability of a material to transfer heat from one surface to another. The unit of heat is 1 joule (J). With increasing humidity and density of a material, its thermal conductivity increases.

Heat capacity - the amount of heat required to heat a body by 1 kelvin" (K).

Mechanical properties of materials.

Strength - the property of a material to resist destruction under the influence of loads or other factors. The tensile strength is the conditional stress corresponding to the greatest load preceding the destruction of the material sample. The tensile strength is determined by loading material samples to destruction on presses or tensile testing machines. Brittle materials are tested mainly in compression, while ductile materials are tested mainly in tension.

Many building materials are characterized by technical conditions so-called grades that coincide in value with the tensile strength (compressive strength). For example, heavy concrete comes in grades (M) 100, 150, 200, 300, 400, 500 and 600 brick-50, 75, 100, 125, 150, etc.

Hardness - the ability of a material to resist the penetration of another, more solid body into it. The hardness of a material does not always correspond to its strength. Materials with different strength limits can have the same hardness. There are several ways to determine the hardness of a material. For example, the hardness of homogeneous stone materials determined on a special scale made up of ten minerals, which are arranged in order of increasing hardness. The material being tested is scratched with scale minerals, and the results are compared with the standard. A steel ball is pressed into metal, concrete and wood with a certain load. The hardness of the material is determined by the depth of indentation or the diameter of the imprint.

Elasticity - the property of a material to change shape under load and restore it after the load is removed. Restoration of the original form can be complete or partial. If the restoration of shape is incomplete, then the material has so-called residual deformations. The elastic limit is considered to be the stress at which residual deformations first reach the value specified in the technical specifications for a given material.

Fragility - the property of a material to collapse under mechanical loads without noticeable plastic deformation. Brittle materials include cast iron, concrete, brick. They are easily destroyed by impacts and cannot withstand high local stresses (cracks form in them), so they are not used for building structures subject to tensile and bending forces.

Fire hazardous properties of materials.

Flammability - the ability of a material to burn or not to burn under the influence of fire. Based on flammability, materials are divided into non-flammable (non-combustible), low-combustible (difficult to burn) and combustible (combustible). Non-combustible materials include materials that do not ignite, smolder or char when exposed to fire or high temperature. If, under the influence of fire or high temperature, materials or structures ignite, smolder or char and continue to burn or smolder only in the presence of an ignition source, and after its removal the burning or smoldering process stops, they are classified as low-combustible. Combustible materials under the influence of fire or high temperature ignite and continue to burn or smolder after the ignition source is removed.

All building materials of inorganic origin are classified as non-combustible, and organic ones are classified as combustible.

2.2 The concept of thermal conductivity and thermal insulation.

Heat transfer or heat exchangeis called the transfer of internal energy from one body to another as a result thermal contact(contact) without doing work

Thermal conductivity- one of the types of heat transfer (energy of thermal movement of microparticles) from more heated parts of the body to less heated ones, leading to equalization of body temperature.

Through this type of heat exchange, heat is transferred through the wall of the house in winter. Since the temperature inside the house is higher than outside it, the most intense thermal oscillatory motion is performed by particles that form inner surface walls. Colliding with particles of a neighboring colder layer, they transfer part of the energy to them, as a result of which the movement of particles in this layer, while remaining oscillatory, becomes more intense. So, from layer to layer, the intensity of particle vibrations increases, and, consequently, their internal energy. Thus, with thermal conductivity, energy transfer in a body occurs as a result of the direct transfer of energy from particles (molecules, atoms, electrons) with higher energy to particles with lower energy.

Heat can be transferred through solid, liquid and gaseous bodies. Metals have the highest thermal conductivity. This is explained by the fact that the carriers of internal energy here, in addition to molecules, are free electrons. Wood, glass, animal and plant tissues conduct heat worse; Liquids have even lower thermal conductivity

(excluding liquid metals, such as mercury): and gases. Thus, air conducts heat thousands of times worse than iron.It is very important to know the thermal conductivity of materials used in the construction of so-called building envelopes

(i.e. external walls, upper floors, floors in the lower floor) and especially thermal insulation materials designed to retain heat in rooms and heating installations.

Heat transfer regulation is one of the main tasks construction equipment. During the cold season, heat is lost in the room due to the thermal conductivity of the walls and air leakage through them, leaving along with the heated air through ventilation ducts and cracks. To ensure that the temperature in residential and production premises corresponded to normal conditions of human life and activity, it is necessary to reduce these losses. For this purpose, the walls of houses are made of materials with low thermal conductivity - natural (wood, reeds, various types of peat, pumice, cork) or artificial (brick, concrete, polystyrene foam, etc.). The thermal insulation properties of these materials are different.

Frame buildings are now widespread, the construction of which requires much less materials than other types of buildings. The basis frame building constitutes a metal or reinforced concrete frame, which plays in the building the same role that the skeleton performs in the body of animals: it absorbs the load. Walls made of heat-insulating porous materials are reinforced on the frame. The pores of such materials are filled with air, so they have a relatively small weight and conduct heat poorly, since the thermal conductivity of air is very low, and air convection in porous materials is impossible.

When producing heat-insulating materials, air bubbles are introduced into the prepared mass. To do this, beat it or add special foam or substances that, when entering into chemical reaction with the prepared mixture, gas bubbles are released. Some porous thermal insulation building materials are produced using a thermal method. For example, in the production of foam glass, glass powder is mixed with a small amount of crushed limestone, poured into metal molds and heated. At a temperature of 550-600 °C, glass powder melts, forming a solid mass. When the temperature reaches 750-780 °C, the decomposition of limestone begins, from which gases are released. Puff up the molten mass, they give it porosity. After hardening, a material is formed that retains all properties. ordinary glass: non-flammability, resistance to moisture and acids, etc. At the same time, this material has new remarkable qualities: it is durable, easy to process - sawn, planed, does not crack when nails are driven into it. The use of thermal insulation materials in industrial and civil construction not only reduces the cost, but also increases the usable area of premises, increases their fire resistance and soundproofing.

2.3 Heat transfer in construction.

The roof, walls and windows are called the external enclosing structures of the building due to the fact that they protect the home from various types of atmospheric influences of low temperatures, solar radiation, moisture, and wind. With the formation of a temperature difference between the inner and outer surfaces of the fence, a heat flow is generated in the fence material, which is directed towards a decrease in temperature. At this time, the fence provides more or less resistance R 0 heat flow. Structures with greater thermal resistance provide better thermal protection. The thermal insulation properties of a wall will depend on its thickness and the thermal conductivity coefficient of the material from which it is built. If the wall consists of several layers (for example, brick-insulation-brick), it thermal resistance will depend on the thickness and thermal conductivity of the material of each layer. The thermal insulation properties of enclosing structures largely depend on the moisture content of the material. Almost all building materials contain tiny pores, which fill with air when dry. With increasing humidity, the pores are filled with moisture, the coefficient of thermal conductivity of which is 20 times greater compared to air, and this leads to a sharp decrease in the thermal insulation characteristics of both materials and structures. In this regard, during the design and construction process it will be necessary to provide measures that would prevent the moisture of structures from precipitation, groundwater and moisture resulting from condensation of water vapor. During the operation of houses, due to the influence of the internal and external environment on the enclosing structures, the materials are not in a completely dry state, but differ slightly high humidity. This inevitably leads to an increase in the thermal conductivity of materials, as well as a decrease in their thermal insulation ability. That is why, when assessing the thermal protection characteristics of structures, it is important to use the real value of the thermal conductivity coefficient under operating conditions, and not in a dry state. The moisture content of warm internal air is higher than that of cold external air, and as a result, the diffusion of water vapor through the thickness of the fence always results from warm room in the cold. If with outside fencing, place dense material that does not allow water vapor to pass through well, then some of the moisture, not being able to escape, will begin to accumulate in the thickness of the structure. And if there is a material near the outer surface that does not interfere with the diffusion of water vapor, then all moisture will be removed from the fence quite freely.

Even at the stage of designing a house, it is necessary to take into account the fact that single-layer walls 400-650 mm thick are made of brick, small blocks of cellular concrete (or expanded clay concrete) or ceramic stones provide a relatively low level of thermal protection (about 3 times less than required). Increased thermal insulation characteristics that satisfy modern requirements, have three-layer enclosing structures. They consist of inner and outer walls made of bricks or blocks, between which there is a layer of heat-insulating material. The outer and inner walls, connected by flexible connections in the form of reinforcing bars or frames laid in horizontal masonry joints, give the structure strength, and the inner (insulating) layer provides the required heat-protective parameters. The thickness of the insulating layer is selected depending on climatic conditions and type of insulation. Due to the heterogeneity of the structure of a three-layer wall and the use of materials with different heat-protective and vapor barrier characteristics, condensation may form within the structure. The presence of the latter significantly reduces the thermal insulation properties of the fence. Because of this, when constructing three-layer walls, it is necessary to provide for their moisture protection. More recently, new regulations on heat conservation have been adopted. This is precisely why the thermal insulation of residential buildings is becoming one of the most important problems in construction today. The problem of thermal insulation is especially acute in cottage and dacha construction, because, if done correctly, it can reduce heating costs by 3 or even 4 times.

The figure shows an example of the distribution of heat loss through various structural elements of a house with an area of 120 m 2

2.4 Classification of thermal insulation materials.

All thermal insulation materials are divided into several large groups:

mineral wool;
glass wool and fiberglass;
gas-filled polymers - foam plastics: polyurethane and polyurethane foam, polystyrene and polystyrene foam, polyethylene, phenol foam, polyester;
thermal insulation from natural materials and their processed products: cork, paper, peat blocks, etc.;
thermal insulation based on synthetic rubber;
thermal insulation from silicon production waste;
thermal insulation panels and designs;
modified concrete: polystyrene concrete, cellular concrete(foam concrete).

Of course, it is best to build from materials that have sufficiently high thermal insulation properties.

And yet, much more often the problem of thermal insulation arises for a brick cottage that is just under construction, or a house that has been built a long time ago. Of course, highly efficient thermal insulation materials are of greatest interest. These usually include materials with an average density within 200 kg/m 3 and K heat less than 0.06 WDm"K). Such materials quickly pay for themselves within 5-10 years of operation, allowing you to save on energy costs.

Issued insulation materials in the form of rolls and soft, semi-rigid and hard mats and slabs, different in density and size.

In the last few years, “stone” ones have become increasingly popular, or to be more precise - basalt wool. This type of cotton wool is environmentally fireproof pure material, characterized by high water-repellent properties, but at the same time vapor permeable. Basalt materials are significantly superior to traditional glass wool in their thermal insulation properties, but, unfortunately, they are more expensive than the latter. These materials belong to the group of fireproof materials. Thermal insulation products made of polymers or paper burn out in a fire in 5 minutes. Insulation materials made of glass wool at a temperature of 650 °C, which is reached in just 7 minutes during a normal indoor fire, melt and sinter into glass bowl. As for basalt-based mineral wool, even at a temperature of 1000 °C it does not melt and does not lose its original shape.

All insulation materials are safe both for production and for use, subject to the recommended operating technology.

Basalt insulation materials are also available in a variety of sizes and types (rolls, hard and soft, mats and slabs) for their more efficient and effective application. Their thermal conductivity coefficient, depending on density, ranges from 0.034 to 0.042 W/(m*K). Quite recently appeared on the Russian market basalt thermal insulation used for insulating roofs, floors and walls, filling partitions, arranging attics, produced in the form of slabs, profile products and, of course, rolls.

Gas-filled polymers are one of the most effective types thermal insulation. The most common and widely used of them is polystyrene foam (expanded polystyrene). The low heat resistance and flammability of foam plastics are not a hindrance when using them in layered structures in combination with brick or concrete. Expanded polystyrene is either produced using the non-press method.

2.5 Thermal insulation properties of materials.

The main indicator of the thermal insulation properties of a material is the thermal conductivity coefficient. This indicator largely depends on the moisture content in it, each percentage of which reduces the coefficient by 4%. In addition, in winter, the moisture present in polystyrene foam boards, freezing and turning into ice, eventually separates the material into individual granules, and this sharply reduces the durability of pressless foam. Unpressed foam is traditionally produced in Russia.

Extruded polystyrene foam does not have these disadvantages. Possessing very low water absorption (less than 0.3%) due to the closed cell structure and high mechanical strength, panels made of extruded polystyrene foam can be used for external thermal insulation, for thermal insulation of underground parts of buildings, foundations, basements, walls, where the use of most other insulation materials is simply impossible due to the capillary rise of groundwater.

Thermal insulation materials with a lower thermal conductivity coefficient

0.06 W/(m-K) pays for itself in an average of 5-7 years of operation due to energy savings.

The table below shows the thermal conductivity coefficients of building materials.

Type of insulation	Coefficient of thermal conductivity,
Solid brick
Fiber cement	0,55
Non-autoclave foam concrete	0,45
Dry sand
Hardwood	0,25
Thermal insulating cellular concrete	0,12
Bituminous asphalt
Ceramics	0,07
Cork insulation	0,047
Ecowool (paper)	0,046
"Penoizol" (foam plastic)	0,04
Basalt wool.	0,039
Glass wool	0.038
Polyethylene foam	0,035
Low-E foam insulation	0,027
Expanded polystyrene	0,027

These materials are impregnated with substances to reduce moisture absorption, fire retardants to make the material non-flammable and antiseptics. They have quite good thermal insulation properties (K t ch =0.078 W/(m-K) and can be used for insulation of external and internal walls and ceilings. The materials are available in the form of panels or ecowool.

3. Practical part.

Materials and research methods.

Studies were carried out at room temperature

Research was carried out using electronic thermometer. Equipment: electric stove. a tripod, a combined digital device with a temperature sensor, and the materials under study. We observed the change in temperature over time and recorded it in a table, then made graphs.

In this work, the heat-conducting properties of several materials are studied.wood, brick, aerated concrete, and also examined the flammability of insulation materials technoNIKOL , polystyrene foam and construction foam.The steepness of the resulting curves characterizes the thermal conductivity of materials as the ratio of the temperature change to the time during which this change occurred.

27,6

23,7

21,6

24,3

Analyzing the obtained graphs of temperature growth, we calculated

thermal conductivity of materials as the ratio of the temperature change to the time during which this change occurred

Material	Thermal conductivity Experimental 0 C/s	Thermal conductivity Tabular W/(m*K)
Brick	0,079	0,56
Aerated concrete	0,062	0,45
Tree	0,055	0.25

Analysis of the graphs and measurement results showed what unique thermal insulation capabilities modern materials have.

4.Fire resistance of materials

To build modern houses, people use various materials: brick, aerated concrete, wood and wood products - particle boards (chipboards), fibreboards (fibreboards), plywood, etc.

For finishing, finishing and facing materials, including polystyrene tiles, PVC and chipboard panels, wallpaper, films, ceramic tiles, fiberglass, polymer materials, products made of synthetics and plastics, etc. Finishing materials create an additional threat to the life and health of people by causing smoke, releasing toxic combustion products and facilitating the rapid spread of flames.

experimental part

Here we tested for flammabilitywood impregnated with fire-fighting antiseptics, TechnoNIKOL insulation, polystyrene foam and construction foam.

Conclusion: Construction foam ignites very easily and produces asphyxiating gas and black smoke.

TechnoNIKOL insulation ignites very poorly, one might say it does not burn at all.

Wood impregnated with antiseptics is much less flammable.

Polystyrene foam burns well and emits a large number of soot

5. Conclusion and conclusions:

The results obtained during the research show what unique thermal insulation capabilities modern materials have and lead to the conclusion about the need to inform and even promote modern building materials among the population. Moreover, in modern construction market High-quality thermal insulation materials are quite widely represented. These insulation materials are environmentally friendly and fire resistant.

Such materials are more expensive and therefore not widely used in construction. In our city, these materials are already used in the construction of new buildings, as well as for insulating existing buildings. Moreover, these materials are used both on large construction sites and in the construction of private houses.

After the research, we came to the conclusion that our house is far from safe, because a fire can occur quickly, since many substances and objects are highly flammable, and it will be accompanied by strong smoke and a high concentration of toxic substances.

Do not use materials marked “G2”, “G3” and “T4” in your homes. This means they are highly flammable and highly toxic.

Remember! Synthetic materials emit very toxic smoke when burned.

Keep your home clean and tidy. Cleanliness and order should be your motto.

Simple rules will help make your home cozy and, most importantly, safe!

Literature

Isachenko V.P., Osipova V.A., Sukomel A.S. Heat transfer. – M.:

Energoizdat, 1981. –416 p.

Filippov L.P. Study of thermal conductivity of building materials. –M.: Moscow State University Publishing House, 2000. –240 s.
Osipova V.A. Experimental study heat transfer processes. –M.: Energy, 2001. –318s.
Internet resources.

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