Thermal characteristic comparison of three-dimensional oscillating heat pipes with/without sintered copper particles inside flat-plate evaporator for concentrating photovoltaic cooling

In this study, a three-dimensional oscillating heat pipe with flat plate evaporator has been designed and experimentally tested for the cooling of concentrating photovoltaic cells. The startup performance, effective thermal resistance, and inclination angle effect on the thermal performance of oscillating heat pipes with/without sintered copper particles in the evaporator section were compared and evaluated. Experimental results showed that porous structures of sintered copper particles on the evaporator can significantly improve the vapor bubble generation and growth rate, and easily produce thin film evaporation to enhance latent heat transfer capacity. When charged with the same volume fraction of ethanol, the three-dimensional oscillating heat pipe with sintered copper particles always outperformed the one without them, especially at the horizontal orientation. The temperature of concentrating photovoltaic cells can be maintained below 57 degrees C at a corresponding heat flux of 5.88 W/cm(2) when the input power is 40 W. In addition, a lowest thermal resistance of 0.145 K/W was achieved by the oscillating heat pipe with sintered copper particles at a filling ratio of 30% under an input power of 100 W. The three-dimensional oscillating heat pipe associated with outstanding heat transfer performance provides a promising candidate for concentrating photovoltaic cooling.