| Abstrakt: |
An experimental study of a low-temperature chamber included measuring the temperature inside and outside the chamber as it was cooled to a temperature of 150 °C and then heated with the cooling unit turned off. In addition, the temperature of a 14.4 kg steel plate placed inside the cooling chamber was measured as it cooled from ambient to the minimum temperature. It is shown that a regular thermal regime is established very quickly in the process of heating the cooling chamber. From this, we can find the equivalent value of the thermal diffusivity coefficient of the thermal insulation of the chamber. Using the analytical solution of the thermal insulation model with the value of the thermal diffusivity obtained in the experiment with a regular thermal regime of heating, it is possible to calculate the temperature distribution in the thermal insulation of the chamber during its cooling. Having an analytical solution for the temperature in the thermal insulation, we find the temperature gradient on the inner wall of the chamber as a coordinate derivative of the expression for the temperature in the thermal insulation. Given the analytical solution for a temperature gradient in the thermal insulation, it is possible to find the heat flow through the inner wall surface, which is equal to the product of the temperature gradient on the inner wall, inner wall surface and the thermal conductivity of the thermal insulation. However, the thermal conductivity of the polyurethane foam insulation can be assumed to be known with a large margin of error. Therefore, to refine the thermal conductivity coefficient of thermal insulation at low temperatures, we will use the results of the experiment to cool a loaded refrigerator chamber. The steel part inside the refrigeration chamber plays the role of a calorimeter. From this, we find the value of the thermal conductivity of the thermal insulation, which is equal to 0.0407 W/(m∙K), and we find the cooling capacity of the refrigerating unit at 150 °С, which is equal to 136 W. [ABSTRACT FROM AUTHOR] |
