Master of DonNTU Pigildina Viktoriya Sergeevna

Theme of master's degree dissertation:
"RESEARCH HEATING ENGINEERING AND FIZIKOTEKHNICHESKIKHZASCHITNYKH OF PROPERTIES OF HEAT-INSULATION MATERIALS WITH THE PURPOSE OF INCREASE OF ENERGOEFFEKTIVNOSTI OF THEIR USE"
Scientific advisor: Greedin Sergey Vasilievich

ACTUALITY
Presently one of most issues of the day is a search and creation of possibilities of the economy use of resources, by power expense measures and engineerings decisions on realization of teplo- and technological processes with minimum thermal losses. A large role is herein played by knowledge of thermophysical properties (TFS) of heat-insulation materials and wares which are already utillized or only are on the stage of development. A thermal isolation is used not only during a technological process on enterprises, but also for the isolation of pipes and in the way of life for the isolation of internal and outward walls, ceilings and floor. It is widely used in energy, housing and public utilities, chemical, oil-reining, metallurgical, food and other industries of industry.

Warming of houses becomes the theme of talks of not only builders and owners of the real estate but also ordinary citizens which care of comfort terms of the residence all more frequent. An insufficient thermal isolation is reason of not only defervescence, and hereupon - increasing expenses for heating but also risk of damage of walls from the frequent frozen solid. Also very important is a question of co-operation of modern thermal isolation with an environment, search of materials which will answer ecological requirements and requirements of social comfort.

AIMS AND TASKS

The primary purpose of work is research heating engineering and physicotechnical protective properties of heat-insulation materials and increase of power effectiveness of their use. One of practical results of researches is drafting of characteristic equalization which would allow in any locality at any climatic terms, for any building to choose the most suitable heat-insulation material and expect his optimum thickness. It would allow considerably to shorten time on the searches of materials, and also to turn to the economic account from the purchase of necessary raw material without surplus.

BASIC PART. RESULTS OF OWN RESEARCHES

Heat-insulation materials (HIM) are build materials and wares, intended for the thermal isolation of constructions of buildings and buildings, and also different technical applications. A basic feature of heat-insulation materials is their high porosity, as a result is a small middle closeness and low heat conductivity. The basic way of decline of power expense on heating of buildings lies in the increase of thermal resistance of non-load-bearing constructions with a help HIM.

Major technical description of heat-insulation materials is heat conductivity is ability of material to pass a warmth through the layer, because thermal resistance a non-load-bearing construction depends straight exactly on it. In number determined the coefficient of heat conductivity of l. On the size of heat conductivity of heat-insulation materials have influence closeness of material, kind, sizes and location of pores (emptinesses) et cetera Strong influence on heat conductivity renders also temperature of material and especially his humidity. In most cases the coefficient of heat conductivity for different materials is determined experimental a way. The row of methods of experimental determination of coefficient of heat conductivity is known. Majority from them is based on measuring of thermal stream and gradient of temperatures in the set matter. The coefficient of heat conductivity is here determined from correlation

It ensues from equalization, that the coefficient of heat conductivity is numeral equal to the amount of heat, which passes in time unit through unit of isothermal surface at a temperature gradient, equal to unit.
Because bodies can have a different temperature, and at presence of heat exchange and in a body a temperature will be up-diffused unevenly, above all things it is important to know dependence of coefficient of heat conductivity on a temperature. Experiments show that for many materials with sufficient for practice exactness dependence of coefficient of heat conductivity on a temperature it is possible to accept linear:

where λ₀ – is a value of coefficient of heat conductivity at the temperature of t₀;
b – permanent, determined experimental a way

In dielectrics with the increase of temperature the coefficient of heat conductivity is usually increased (see picture 1). As a rule, for materials with a by volume high-slay more high value has a coefficient of heat conductivity. He depends also on the structure of material, his porosity and humidity. From porosity of structure of heat-insulation materials application of law Fur'e to such bodies is to a certain extent conditional. The presence of pores in material does not allow to examine such bodies as continuous environment. Conditional is also a size of coefficient of heat conductivity of porous material. This size makes sense coefficient of heat conductivity of some homogeneous body, through which at an identical form, sizes and temperatures the that amount of heat passes on scopes, what through this porous body. The coefficient of heat conductivity of powdery and porous bodies strongly depends on their b.d.. For example at growth of closeness from 400 to the 800 кг/м³coefficient of heat conductivity of earth-flax is increased from 0,105 to 0,248 Vt/m•grad. Such influence of closeness on the coefficient of heat conductivity is explained that heat conductivity of filling pores air considerably less than, than hard components of porous material.

Picture 1 is Dependence of coefficient of heat conductivity on a temperature

The effective coefficient of heat conductivity of porous materials strongly depends also on humidity. For moist materials coefficient of heat conductivity what for dry and waters individually. For example, for a dry brick λ=0,35, for water λ=0,60, and for the moist brick of λ=1,0 vt/m•grad. This effect can be explained the konvektivnym transfer of warmth, to arising up due to capillary motion of water into porous material and partly that absorption CPLD moisture has other descriptions as compared to free water.
The coefficient of heat conductivity of build and heat-insulation materials is had values, lyings approximately scope from 0,023 to 2,9vt/m•grad. Materials with the low value of heat conductivity usually and used for a thermal isolation and named heat-insulation.
CONCLUSIONS

As a result of research work were collected and studied materials on questions, to related to the theme of master's degree work: the questions of the use of heat-insulation materials of different type are considered, their thermophysical descriptions and properties are investigational depending on different operating and climatic factors, also development and making of experimental fluidizer goes receipt of own results in this area.
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© DonNTU 2009 Pigildina Victoriya.

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