Heat Transfer Analysis And Numerical Simlation On Liquid-immersion Solar Receiver In Medium And High CPV Systems

Based on the fact that concentrated photovoltaic (CPV) systems have the heatdissipating problem, liquid immersion cooling was proposed to be used in CPVsystems in order to improve the efficiency of power output. In this paper,experimental and numerical simlation works on heat transfer performance for mediumand high liquid-immersion CPV systems were investigated.A smale-scale plane mirror linear CPV system with the concentrated illuminationof11.7suns was established as the outdoor experimental platform, and thetemperature and electrical characteristics of the cell array were experimentallyinvestigated. Experimental results showed that liquid immersion cooling could keepthe maximum temperature of the cell array no more than16.5℃and the temperaturenon-unifornity of less than3℃under direct normal irradiance of910W/m~2,8.2℃liquid inlet temperature and inlet flow rate of0.544L/s; at inlet flow rate of1.08L/s,the average heat transfer convective coefficient can be achieved at750W/(m~2·K); thecell temperature almost had a linear relationship with liquid inlet temperature.Additionally, the output power could be stabilized at the level of around20W underDNI of950W/m~2, wind speed of1m/s and12.3~18.7℃cell temperature; thetemperature coefficient of open circuit voltage for the liquid-immersed cell array was-9.7mV/℃; no obvious deterioration of cell module electrical parameters wasobserved after being immersed in silicon oil.For purpose of guiding and designing a more efficient linear CPV system,three-dimensional geometrical model and mathematical models of the prototypicalreceiver were built. The simulated results showed that the liquid inlet temperature hadan effect on the cell temperature, but not on the temperature non-uniformity;increasing fluid inlet velocity could enhance the heat transfer and resulted in afavourable cell temperature, but higher liquid inlet velocity caused more pressure dropwhich required more pump power, and the suitable inlet velocity was1.0m/s; thehigher heat load on cells led to a higher cell temperature and a worse temperatureuniformity; downsizing the distance from receiver inlet to the cell array couldimprove the heat transfer performance and caused a lower cell temperature; loweringthe receiver channel could enhanced the heat transfer and thus decreased cell temperature, but reducing the channel height induced obvious pressure drop betweenreceiver inlet and outlet. By integrated consideration of cell temperature and pressuredrop, the channel with10mm was the best choice.For the sake of learning the capacity of liquid immersion cooling for high CPVsystems and better understanding the law of micro fluid flow and heat transfer inliquid immersion cooling, numerical investigations on the heat transfer performanceof a cylindrical liquid-immersion receiver applied in250X dish system were done.The simulated results showed that the addition of fins could efficiently reduce the celltemperature and improve the cell module temperature uniformity. The simulationresults for the finned module showed that increasing fluid inlet velocity caused lowerand more uniform cell temperature, but resulted in greater pressure drop; fin heightand fin number could affect the heat transfer area and flow mode inside the receiver,and a fin height of4mm and a fin number of11was recommended for optimalconfiguration.