RU2490619C1 - Method of determining efficiency factor of super-thin liquid heat-insulating coatings - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: efficiency factor of super-thin liquid heat-insulating coatings is determined using a multilayer plane-parallel wall. The problem is solved based on the principle of determining specific heat flow with and without insulation and using the formula $${\eta }_i=1-\frac{q_{withi}}{q_{withacti}}$$

to find the efficiency factor of super-thin liquid heat-insulating coatings.

EFFECT: enabling determination of the efficiency factor of heat insulation in conditions imitating operation of heat insulation in real conditions.

1 dwg

Description

The invention relates to the field of research and analysis of the thermophysical properties of materials, and can be used to determine the efficiency coefficient of ultrathin liquid thermal insulation coatings - η _u .

A known method for determining the efficiency coefficient of ultra-thin liquid heat-insulating coatings at existing facilities in the production of energy audit of heat loss and the efficiency of thermal insulation of pipelines.

$${\eta }_u=\mathrm{one}-\frac{q_{cu}}{q_{bu}}$$

where: q _cu and q _bu are the specific heat fluxes with and without thermal insulation, respectively.

Here we consider a pipeline covered with thermal insulation, inside which a working medium flows at a certain temperature, which is necessary for the consumer.

(Zlobin A.A., Kuryatov V.N., Maltsev A.P., Medvedeva I.Yu. Romanov G.A. Examples of energy inspection of industrial enterprises // "PRACTICE OF ENERGY AUDIT AND ENERGY SAVING", 2008, No. 4 (8) . - S.20-21).

The method determines the coefficient of thermal insulation efficiency at existing facilities and does not give an answer to the determination of the coefficient of thermal insulation efficiency in laboratory conditions, which is necessary to know before applying thermal insulation in production.

The invention is aimed at determining the efficiency coefficient of ultrathin liquid heat-insulating coatings - η _u in laboratory conditions, close to real.

The result is achieved by the fact that the method for determining the efficiency coefficient of ultrathin liquid heat-insulating coatings is that two layers of material of the same thickness and thermal conductivity are fixed on a heat source, the temperature of the heat source is measured t _t , the temperature between two layers of material t, then fixed on the outer surface the upper layer of the material a thin metal plate, coated with an ultra-thin liquid heat-insulating coating, measure the temperature in the contact surface of the upper its material layer and a metal plate with thermal insulation t _u , the temperature between two layers of material when using thermal insulation t ^* and determine the efficiency coefficient of an ultrathin liquid thermal insulation coating - η _u according to the formula:

$${\eta }_u=\mathrm{one}-\frac{t^{*}-t_u}{t_t-t}\left(\mathrm{one}\right)$$

where: η _u is the efficiency coefficient of an ultrathin heat-insulating coating,

t _t - temperature of the heat source without insulation,

t is the temperature between two layers of material without thermal insulation,

t ^* is the temperature between two layers of material when using thermal insulation,

t _u - temperature in the contact surface of the upper layer of the material and the metal plate with thermal insulation.

A device for determining the coefficient of thermal conductivity of ultrathin liquid heat-insulating coatings η _u is shown in (Fig. 1).

The device is an installation (figa), which is a multilayer plane-parallel wall, including two layers of the same material of the same thickness δ and equal thermal conductivity λ: the lower layer 1 and the upper layer 2 mounted on top of each other. A thin layer 2 is fixed on the upper layer 2 a metal plate deposited on its outer surface of an ultra-thin liquid heat-insulating coating 4 (hereinafter referred to as thermal insulation) (Fig. 1b). The thickness δ of the plate must be such that it does not warp from thermal stresses. Due to the high coefficient of thermal conductivity, a thin metal plate practically does not affect the results of measured temperatures. Since the thermocouple itself and its measuring junction have certain dimensions, additional metal plates are installed between the layers, with a thickness compatible with the dimensions of the temperature junction of thermocouples. Slots are made in these plates for thermocouples, providing temperature measurement approximately in the center of the layer. All this is installed on a temperature-controlled heat source 3, providing a snug fit of all layers. Installation should exclude the influence of the external environment on the side surfaces of the layers.

The method for determining the efficiency coefficient of an ultrathin liquid heat-insulating coating is as follows. The temperature-controlled heat source 3 is turned on and, upon reaching the calculated thermostationary mode, thermocouple readings are taken: temperature t _{t of} heat source 3, temperature t between layers 1 and 2 (Fig. 1a). After installing the metal plate with thermal insulation 4 on the upper layer 2 (Fig.1b), measure the temperature t _u in the contact surface of the upper layer of material 2 and the metal plate with thermal insulation 4 and the temperature t ^* between the layers 1 and 2 with insulation at the same operating mode heat source (temperature values are taken from a personal computer monitor, where they are transferred from thermocouples through a TPM138 meter-controller and an AC3-M-220 interface converter using the SCADA-system program (process controller). As a material for layers and enjoyed windowpane with δ = 0,0059 m and λ = 0,74 W / m ° C).

Then determine the specific heat flux without thermal insulation (Fig. 1a):

, $$q_{bu}=\frac{\lambda }{\delta }(t_t-t)$$

,

where: t _t and t are the temperatures of the heat source and between the layers of an uninsulated multilayer wall (Fig. 1a).

,Specific heat flux is determined using thermal insulation (Fig. 1b) during thermostationary mode of operation of a heat source: $$q_{cu}=\frac{\lambda }{\delta }\left(t^{*}-t_u\right)$$

,

where: t ^* and t _u are the temperatures between the layers in the contact surface of the layer and insulation at the same mode of operation of the heat source.

Substituting their values in (1), we obtain:

$${\eta }_u=\mathrm{one}-\frac{t^{*}-t_u}{t_t-t}$$

The proposed method for determining the efficiency coefficient of an ultrathin liquid heat-insulating coating λ _{u is} quite simple and affordable. Thermal insulation works as a real production facility. There is no need to measure the temperature on its surface, which, due to the thermophysical properties of thermal insulation, is practically difficult to measure. The method allows to determine the coefficient of thermal insulation efficiency η _u in a mode that simulates the thermal insulation in real conditions, which will allow you to confidently use ultra-thin liquid thermal insulation coatings in production, using their positive qualities, and leads to the development of new even better materials.

Claims (1)

A method for determining the efficiency coefficient of ultrathin liquid heat-insulating coatings, namely, that two layers of material of the same thickness and thermal conductivity are fixed to a heat source, the temperature of the heat source is measured t _t , the temperature between two layers of material t, then a thin metal is fixed on the outer surface of the upper layer of the material a plate coated with an ultra-thin liquid heat-insulating coating, measure the temperature in the contact surface of the upper layer of the material and metallic thermal insulation plate t _u , the temperature between two layers of material when using thermal insulation t ^* and determine the efficiency coefficient of an ultrathin liquid thermal insulation coating η _u according to the formula
$${\eta }_u=\mathrm{one}-\frac{t^{*}-t_u}{t_t-t},$$

where η _u is the efficiency coefficient of an ultrathin heat-insulating coating,
t _t - temperature of the heat source without insulation,
t is the temperature between two layers of material without thermal insulation,
t ^* - temperature between two layers of material when using thermal insulation,
t _u - temperature in the contact surface of the upper layer of the material and the metal plate with thermal insulation.