Comparative energy, exergy and entropy generation study of a minichannel and a conventional solar flat plat collectors

Abstract

Considering the importance of using renewable energies for human societies, it is necessary to optimize the devices used. Flat plate solar collectors play a prominent role in the domestic and industrial sectors, so it is very important to enhance their performance. Changing the structure of the collector and using minichannel flat plate collectors (MFPCs) instead of sheet and tubes conventional flat plate collectors (CFPCs) is one choice. This study examines and compares the performances of a MFPC and a CFPC based on the energy, exergy and entropy generation perspectives. The working fluid is water and the fluid flow is laminar. Both collectors have the same contact surface between the working fluid and the inner surface of the riser tubes or the minichannels. In order to solve the equations, a thermal model is developed and the engineering equation solver is used. The results show that for all of the investigated conditions, the thermal and exergy efficiencies of the MFPC are higher than those of the CFPC and the maximum energy and exergy superiorities of the MFPC are 13.8 and 14.08 %, respectively. The study of the energy performance criteria shows that the MFPC is more suitable at lower volumetric flow rates and higher inlet fluid temperatures. Investigating the entropy generation and exergy destruction indicates that for every similar case the entropy generation and exergy destruction of the MFPC are lower than those of the CFPC. These interpretations, which are based on the energy, exergy, entropy generation and exergy destruction evaluations, recommend utilization of MFPCs instead of CFPCs.