Study On Solar Parabolic Trough Collector Based On MWCNT Nanofulid

The trough concentrating solar power(CSP)is a new type of clean power generation technology that can efficiently convert solar energy into thermal energy.It is one of the important ways to solve the current energy crisis and environmental pollution caused by fossil fuel.The collector is the core equipment in converting solar energy into thermal energy.The application of nanofluid is an effective measure to improve the efficiency of the parabolic trough solar collector.In this paper,the numerical simulation of the trough solar collector based on multi-walled carbon nanotubes/heat transfer oil nanofluids,as well as related experimental research was carried out.Based on the Monte-Carlo-ray-tracing(MCRT)method,the optical simulation software,Sol Trace was used to build the 3-D optical model of trough collector.The collector tube radius the size of evacuated glass envelope and concentrator was studied to investigate the effects on the collector heat flux distribution and optical efficiency.The results show that the optical efficiency of the collector will decrease as the radius of the collector tube decreases;compared with the trough collector with evacuated glass envelope,the optical efficiency of the bare tube collector is 10% higher on average.As the focal length of the concentrator increases,the optical efficiency of the trough collector first decreases slowly;when the focal length continues to increase increases,the optical efficiency begins to decrease sharply;when the width of the concentrator increases,the heat collector The optical efficiency of the condenser increases first and then decreases,and reaches the maximum when the width of the condenser is 2.5m.The thesis applied computational fluid dynamics(CFD)software to build the 3-D model of parabolic trough solar collector tube.Based on the heat flux distribution acquired by the optical simulation,the effects of multi-wall carbon nanotube concentration and different inlet operating conditions on the heat transfer performance of the collector were studied.The results show that the thermal efficiency of the collector will decrease as the inlet temperature increases and the inlet velocity decreases;meanwhile,the addition of multi-walled carbon nanotubes significantly changes the thermal performance of the heat transfer fluid.In general,there is a most suitable concentration of carbon nanotubes to optimize the thermal efficiency of the collector.In order to investigate the effect of different nanofluid on the performance of collector,the paper also numerically studied the collector based on aluminum oxide/heat transfer oil nanofluid,different nanoparticle concentrations and operation conditions were investigated.The performance of the trough collector based on aluminum oxide /heat transfer oil nanofluid and multi-walled carbon nanotubes/ heat transfer oil nanofluid were compared and analyzed.The results show that,compared with the ordinary metal nanoparticles,multiwalled carbon nanotubes have unique advantages in improving the performance of the heat transfer fluid,and can greatly improve the thermal efficiency of the collector.Finally,in order to verify the effectiveness of the numerical simulation,the thesis applied multi-walled carbon nanotubes/ heat transfer oil nanofluid as the heat transfer fluid to carry out experiment of the trough solar collector,and investigated the mass flow rate and inlet temperature and t the addition of carbon nanotubes on the performance of the collector,it proved that simulation result is agree with the experimental results perfectly.