Optimization And Application Of HCPVT Microchannel Heat Exchanger System Based On Nanofluidics

The contradiction between growing energy demand for energy and carbon emission has become an important factor restricting the development of productivity,solar energy,as a rich renewable energy source,can alleviate the growing demand for energy,but also put forward higher requirements for the conversion efficiency of solar energy utilization equipment.In this paper,for the effect of negative temperature coefficient of high-power concentrated three-junction gallium arsenide cells,hybird nanofluids were selected as the heat exchange working fluid,combined with the forced convection heat transfer of high efficiency microchannel to effectively cool the photovoltaic cells bearing high heat flow density.The specific work content is as follows:Firstly,three surfactants were used to prepare carbon tube nanofluids and zinc oxide nanofluids,as well as zinc oxide-carbon tube hybird nanofluids.The types and proportions of surfactants suitable for each nanofluidic were determined.The effects of p H and ultrasonic time on the stability of each nanofluid,using particle size,potential and transmittance as evaluation indexes,were analyzed,and the optimal preparation scheme of each nanofluid was obtained.The results show that under the premise of determining the type and proportion of surfactants,elemental nanofluids have better stability in acidic base liquid environment,and hybird nanofluids have better stability in alkaline base liquid environment.With the increase of ultrasonic time,the particle size of nanofluids first decreases and then slowly increases,and the higher the proportion of carbon tube particles,the longer the ultrasonic time required to reach the minimum particle size.Secondly,the heat transfer characteristics of hybird nanofluids in microchannels were analyzed,and the structure of individual microchannels was optimized by orthogonal test combined with matrix analysis method,so that the field synergy angle of the optimized microchannel heat exchanger was reduced to 78.4°.The results showed that when the content of carbon tube nanoparticles in hybird nanofluids is high,the convective heat transfer coefficient is higher and the thermal resistance is smaller.When the ratio of carbon tube particles to zinc oxide particles is 8:2,the maximum enhanced heat transfer factor can reach1.3.The type of working fluid has the most significant effect on the field synergy angle,and the significance can reach 0.52,indicating that the use of nanofluids with high thermal conductivity is an effective method to reduce the field synergistic angle.Thirdly,the cell matrix arrangement scheme is proposed,and the physical model of the heat exchanger is established according to the optimized internal structure of the microchannel.The influence of heat exchanger channel number on the heat transfer characteristics of different cell matrix systems was analyzed,and the most suitable number of microchannels was selected.On this basis,the cell power and photoelectric efficiency of each system under different direct solar irradiation intensities are calculated,and the feasibility of establishing a training sample database of HCPVT system prediction model based on simulation calculation is also proved.Finally,the neural network prediction model of HCPVT system is established,the accuracy and reliability of the prediction model is optimized,and the optimized prediction model is used to predict the range of input parameters,and the influence of different working conditions on the cell output performance of HCPVT system is analyzed according to the prediction results.The results show that when the number of training samples is 80 and the number of hidden layers is 6,the coefficient of determination of the prediction model is greater than 0.95,and the average relative error is less than 1%.Compared with the standard genetic algorithm and quantum genetic algorithm,it is found that the prediction of the three output layers using the quantum genetic algorithm is more accurate,which can better balance the sensitivity of different output layers to weights and thresholds,so as to improve the overall prediction accuracy and make the prediction more reliable.When the direct solar irradiation intensity is 1000W·m^-2 and working fluid temperature of 25°C,the working fluid flow rate is increased from 0.01m·s^-1 to 0.2 m·s^-1,the power of the three cell systems is increased by 1.09%,0.53%and 0.27%,and the photoelectric efficiency is increased by1.21%,0.43%and 0.49%,respectively,which provides a certain theoretical basis for the setting of actual system operating parameters.