Research On The Performance Of Solar Collectors With Ionic Liquid-Based Nanofluids

1-ethyl-3-methylimidazole diethyl phosphate?[EMIM][DEP]?is a kind of Ionic liquid,which has the advantages of non-toxicity and weak corrosion,and it's friendly for the environment.[EMIM][DEP]and water have been used as new working fluid of absorption refrigeration and heat pumps.The ionic liquid[EMIM][DEP]and water have been used as working fluid of heat pumps.A series of nanofluids were prepared in this paper in order to supply heat for absorption refrigeration and heat pumps,which contained[EMIM][DEP]/H₂O system and single walled carbon nanotubes?SWCNT?.And the performance of these nanofluid systems used as working fluid of direct absorption solar collectors was explored in this paper.In this paper,SWCNT was used without surface modification,and it was evenly dispersed in the[EMIM][DEP]/H₂O binary system by stirring and ultrasonic cleaning.The mass fraction of SWCNT inside the nanofluids were 0.01%,0.02%,0.03%,0.04%and 0.05%.An ultraviolet/visible/near-infrared spectrophotometer was used to measure the transmittance of the nanofluid samples under different optical paths,and the extinction coefficient was calculated.On this basis,the absorption efficiency was calculated and data fitted using the photothermal conversion theory.The results show that the addition of a small amount of SWCNT can significantly improve the photo absorption performance of the base fluid.The extinction coefficient can reach 0.986 when the mass fraction of SWCNT is 0.05%and the optical path is 10mm.With the addition of a small amount of nanoparticles,solar radiation is basically absorbed.The extinction of photo through the fluid is mainly dominated because of the absorption of photo by SWCNT,and the effect of scattering is much less.A series of solar-collector tube models covered with single-layer and double-layer?hollow?glass was established in this paper.The heat collection process of the nanofluids inside solar-collector tubes was simulated by using ANSYS^?Fluent.The Influencing factors of the temperature rise of the fluid inside the solar-collector tubes and the efficiency of the tubs were discussed,which included the concentration of SWCNT,the height of the fluid region in the tubes,the velocity of the fluid,the wind speed and the form of the covering glasses.The simulation results show that:under certain operating conditions,the fluid in the collector can reach the required temperature for absorption refrigeration and heat pump after absorbing solar radiation.When the other conditions are the same,the outlet temperature and thermal efficiency increase when the mass fraction of the SWCNT increases;the outlet temperature generally decreases,and the thermal efficiency increases when the height of the fluid channel increases;the outlet temperature and thermal efficiency decrease when the ambient wind speed increases.At the same time,compared with the solar-collector tubes only covered with the single-layer glass,the tubes covered with double-layer glass can make the fluid reach a higher outlet temperature and thermal efficiency,and the higher the ambient wind speed,the more obvious the effect of heat preservation.The experimental and simulation results show that the nanofluid prepared in this paper can be used as the working fluid of the direct absorption solar collector and can meet the heat supply requirements of absorption refrigeration and heat pump.