Investigation On Thermal Performance And Application Of Microchannel Heat Sink Using Nanofluid

The availability of solar energy was the ideal energy source to alleviate the growing demand for power production systems,which can produce electrical and thermal energy due to its cleanness and richness.In the solar power generation operation system,in order to improve the photoelectric conversion efficiency,a solar high-power concentrating system was usually used on the surface of the battery.Although this measure increased the energy flow density,it caused the temperature and thermal stress on the surface of the battery to rise,jeopardizing the safety of the entire system.Therefore,it is necessary to arrange an efficient heat sink on the surface of the battery to improve the energy conversion efficiency.For the micro-channel cooling system of solar cells,this article selected different nano-fluids as a new type of cooling medium for thermophysical properties testing and heat transfer enhancement experiments and theoretical studied,so as to provide reliable experimental and theoretical basis for the use of micro-channel cooling systems.The main contents included:In this paper,carbon nanotube particles were selected,and four different types of dispersants were added to prepare DB-CNTs,CTAC-CNTs,SDS-CNTs,Tx-100-CNTs nanofluids,Then,the effects of ultrasonic oscillation time,the ratio of carbon tube to dispersant and the days of placement on the stability of nanofluids were studied.Transmission electron microscopy,average particle size,Zeta potential and ultraviolet-visible spectrum were used to evaluate its stability.The results showed that the original multi-walled carbon nanotube fluid had poor hydrophilicity and the particles were entangled with each other through TEM observation;when the oscillation time was about 60min,the measurement results of Zeta potential and average particle size were consistent,CTAC-CNTs Nanofluid obtained the highest stability,and the content of carbon tubes had a small effect on the oscillation time within a certain range;When the ratio of carbon tube to dispersant of DB-CNTs,CTAC-CNTs,SDS-CNTs and Tx-100-CNTs was 1:2,1:2,1:1,1:2 respectively,the particle size showed the minimum value and the zeta potential reached the maximum value;the stability of nanofluids was analyzed by absorbance.All the samples had obvious absorption peaks in the wavelength range of 250-350.CNTs nanofluids had obvious absorption peaks in the wavelength range of 250-350,indicating that the addition of dispersants had high stability.The thermal conductivity,density and viscosity of nanofluids were studied.The optimal dispersant type and the mass ratio of CNTs to dispersant were further tested and their long-term stability was analyzed.The results showed that the thermal conductivity of CTAC-CNTs nanofluid reaches its maximum value at 60 min;With the increase of dispersant content,the thermal conductivity of 0.5wt%-CNTs nanofluid had a peak value,and the nanofluid containing DB dispersant had the highest thermal conductivity,the thermal conductivity decreased by 4.32%after being left for 30 days;the mass fraction of the carbon tube increased the thermal conductivity and viscosity of the nanofluid.The viscosity of the carbon nanotube fluid was higher than that of the Si O₂nanofluid.The microchannel heat exchange system was built,water and nanofluid were used as heat exchange materials for experiments.The feasibility of the experiment was verified by simulation and simulation through ANSYS software.The results showed that the simulation values of water and Si O₂fluid outlet temperature are in good agreement with the experimental values;With the increase of Reynolds number,the heat transfer ability of nanofluids was enhanced compared with that of water channels.When Re=178,the heat transfer coefficient of 0.3wt%-CNTs nanofluids was 30.5%higher than that of Si O₂nanofluids,that is to say,adding nanoparticles can enhance the heat transfer of channels;Combined with the engineering practice,aiming at the cooling problem of Ga As photovoltaic cell in Fresnel CPVT system,simulation calculation was performed by Trace Pro and Ansys software,and the entranspy theory was introduced.The influence of the ratio of transverse to longitudinal,the position of the inlet and outlet of the channel,the position of the batteries and the heat exchange quality on the temperature of the back of the plate,the equivalent thermal resistance,the thermal stress and the thermal strain were analyzed.The results showed that the thermal stress was greatest in the contact area of the cell;when the aspect ratio was 0.25,the entrance and exit position was type I,and the cell position y=-4,the heat transfer effect was the best.