Numerical Simulation of Heat Transfer Using Cooling Roof Panels

Roof cooling can be used in coffered roofs, acoustic panels, as active cooling plasterboard attached to a standard metal structure designed for lowered roofs, or as a system of cooling register under the plaster. The roof cooling system works on the principle of heat transfer through a large active area and there is no unpleasant air flow than with conventional air conditioning. For technological reasons, very often pipes with a heat transfer medium are attached to a sheet metal of various materials, the thermokinetic properties of which significantly influence the intensity of the heat flux dissipated by the cooling system. The paper presents a numerical analysis of heat transport using stainless steel and aluminium sheets as the supporting sheet, as well as the influence of different ways of installing large panels under the roof.

Functional Dependence of Thermodynamic and Thermokinetic Parameters of Refrigerants Used in Mine Air Refrigerators. Part 1 – Refrigerant R407C

The authors of this article dealt with the issue of modeling the thermodynamic and thermokinetic properties (parameters) of refrigerants. The knowledge of these parameters is essential to design refrigeration equipment, to perform their energy efficiency analysis, or to compare the efficiency of air refrigerators using different refrigerants. One of the refrigerants used in mine air compression refrigerators is R407C. For this refrigerant, 23 dependencies were developed, determining its thermodynamic and thermokinetic parameters in the states of saturated liquid, dry saturated vapour, superheated vapor, subcooled liquid, and in the two-phase region. The created formulas have been presented in Tables 2, 5, 8, 10 and 12, respectively. It should be noted that the scope of application of these formulas is wider than the range of changes of that refrigerant during the normal operation of mine refrigeration equipment. The article ends with the statistical verification of the developed dependencies. For this purpose, for each model correlation coefficients and coefficients of determination were calculated, as well as absolute and relative deviations between the given values from the program REFPROP 7 (Lemmon et al., 2002) and the calculated ones. The results of these calculations have been contained in Tables 14 and 15.