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CFD Analysis of Heat Transfer Enhancement in a Flat-Plate Solar Collector with Different Geometric Variations in the Superficial Section

Abstract:

Nowadays, there is an increasing need for improving the inefficient ways for obtaining thermal energy from renewable sources to fulfil the industrial and typical needs in heat transfer processes that may be covered using solar assisted heat pumps due to their appropriate performance in the thermal energy transfer process. To improve the efficiency of the collector/evaporator by increasing the heat flux to the refrigerant, in this research, a numerical and computational fluid dynamics (CFD) analysis is conducted with geometrical variations in the surface section of a collector/evaporator. The performance was compared to the results of a base case, replicating its limit and environmental conditions such as the initial temperature of 5.5 °C, incident solar radiation of 464.1 W·m-2, the operating temperature of 17.6 °C and other parameters. The surface geometrical variations involved in this study show a surface area similar to the base case. However, different lengths of the fluid path were considered due to the new geometrical shapes represented with less thermal resistances and correct distribution of the fluid in the collector/evaporator, obtaining temperature variations of 3.78, 5.47, 5.56 °C and a maximum value of 5.63 °C, including the corresponding variation of the heat flux. Considering the geometric changes in the superficial section of a flat-plate solar collector, it is possible to implement these variations in different kinds of heat exchangers in order to analyze the efficiency in these devices and the impact in the global systems where the heat exchangers are used