Study On The Effect Of Different Condensers On Loop Heat Pipe PV/T System

Loop heat pipe Photovoltaic/Thermal(LHP-PV/T)system is one of the measures to solve the problem of water pipe freezing crack.The concentric double-tube heat exchanger(CDTHE)proposed in our previous work addresses the limitations of the large-scale combination application of conventional LHP-PV/T systems combined with buildings.The flow resistance of working fluid in CDTHE is large because of the long pipe,and many elbows.Therefore,the system performance has the potential to be improved.Based on this,a novel non-concentric multi-tube heat exchanger(NMTHE)as the condenser of the LHP-PV/T system was proposed in this paper,which improves the performance of system by reducing the flow resistance of the working fluid.The main works are as follows:(1)Experimental platform was designed and built to explore the performance difference between CDTHE-LHP-P V/T and NMTHE-LHP-PV/T system.Experimental results show that compared with the CDTHE-LHP-PV/T system,the thermal efficiency,the electrical efficiency,the primary energy-saving efficiency and the exergy efficiency of NMTHE-LHP-PV/T system relatively increase by 17.76%,2.1%,10.05%and 3.64%.(2)Mathematical models for two systems are established and verified.Then the performance of the two systems under different solar radiation and ambient temperature is explored.The results show that compared with the CDTHE-LHP-PV/T system,the performance superiority of the NMTHE-LHP-PV/T system is more prominent under lower solar irradiation and at lower ambient temperature,especially the superiority in the thermal efficiency and primary energy-saving efficiency.Besides,the annual performance of the two systems in four cities in different regions of China is predicted.The results show that the performance superiority of the NMTHE-LHP-PV/T system is particularly prominent in Beijing and Urumqi,and it is very suitable for year-round operation in North China such as Beijing.(3)Further,the parameters of the NMTHE-LHP-PV/T system with better performance are analyzed.The influences of parameters such as length of condenser,diameter of the inner tubes of condenser,number of evaporating tubes,diameter of the evaporating tubes,type of working fluid and thickness of air gap on the system performance were simulated and studied,and the suggested values were given,which provided a reference for the optimization design of the system.