| Battery surface energy flow density was improved by fresnel concentration PV/T system, obtaining higher photoelectric conversion efficiency and reducing the cost of photovoltaic power generation, however, the temperature of the battery was increased and the thermal stress was formed, causing battery failure or damage. Therefore, in this paper, the spiral microchannel heat sink was used to cool the GaAs cell. A coolant with nanofluids, it had the characteristics of higher thermal conductivity, and the effect of nanofluids for heat transfer, flow and system performance were analyzed. The main research contents include:Preparation of SiO2 nanofluids by two step method, Particle size distribution, zeta potential and conductivity was measured through the experiment, the influence factor and the change law of the nanofluids to improve the heat conduction performance were analyzed. The results showed, as mass fraction increases, the rise of temperature, SiO2 nanofluids thermal conductivity gradually became larger. After 12 days, the fluid agglomeration of the mass fraction of 1%~3% was less, the reduction of thermal conductivity was small, the better suspension stability. The thermal conductivity of the nanofluids through the high pressure micro jet was higher than the ultrasonic wave.Research on the physical model of Ga As cell by using nanofluids spiral micro channel cooling, the cooling process of nanofluids with different particle sizes, different mass fractions and different flow states was simulated by Ansys software. The law of heat transfer enhancement by nanofluids was evaluated through the field synergy angle, which included by the velocity field and the temperature field. The analysis results showed, under the premise of meeting the cooling requirements, with small particle size, Reynolds number and large mass fraction, the nanofluids field synergy angle was small.From the point of view of cooling fluid flow and heat transfer, the heat transfer and flow state of the fluid were reflected by the Nusselt number, Reynolds number, and the heat transfer enhancement factor. The results showed that the more uniform energy flow density was, the better the heat transfer performance of the cooling structure was, the lower the pressure drop was. At the same time, the smaller the particle size, the mass fraction of 6~8%, the larger effect was of the heat transfer than pressure drop.Based on the study of the theory of microchannel cooling and enhanced heat transfer, this paper analyzed the performance of the high concentration PV/T system. Results showed that mass fraction of 5%, electric efficiency of the system reached its peak, SiO2 and Al2O3 nanofluids cooled, the value were 32.37% and 32%, respectively. When the Reynolds number is 600, thermal efficiency and comprehensive efficiency reached its peak, SiO2 and Al2O3 nanofluids cooled,the thermal efficiency were 50.27% and 47.26%, the comprehensive efficiency were 86.61% and 84.27%, respectively.Finel high concentration PV/T test system was established. Through monitoring the temperature of the battery, radiator outlet fluid temperature, voltage and current etc, the influence of different mass flow cooling fluid on the performance of the system was analyzed. The experimental results showed that with the increase of the mass flow rate of the cooling fluid, the temperature of the battery and the outlet of the radiator was decreased, the value of waste heat recovery was decreased, but the power and the electric efficiency were improved. |
PDF Full Text Request