Design And Operation Characteristics Of Solar Collector Coupling Pulsating Heat Pipe And CPC

Pulsating Heat Pipe(PHP)has the advantages of simple structure,low cost and strong ability of heat transfer,it has huge potential in the field of solar collector,electronics cooling and spacecraft cooling.The premise of stable and efficient work of PHP is the high heat flux density of evaporation.Based on the analysis of the experimental results of the solar heat collector with similar pulsating heat pipe structure from the scholars at home and abroad,it is found that the heat transfer performance of the PHP can be improved by the enhancement of the heat flux in the evaporation section.The introduction of appropriate concentration ratio of Compound Parabolic Concentrator(CPC)can increase the heat flux density of evaporation section without complicated solar tracking system.Based on this,a new type of PHP solar collector equipped with a CPC has been put forward and designed,modeling analysis is carried out on the collector physical structure parameters and the thermal performance theory analysis and experimental study on the collector,the main results and conclusions are as follows:(1)A new type of PHP solar collector equipped with a CPC has been put forward and designed,and the heat flux in evaporation section of PHP as the evaluation index of the heat transfer performance is come up with.(2)The thermal performance of the collector is analyzed theoretically,and the thermal efficiency of the solar collector can reach the maximum of 76.18%,and the performance is similar to the vacuum tube collector performance but higher than the flat collector.The results show that the collector heat leakage loss is mainly affected by wind speed,the thickness of the glass plate,the thickness of the insulation layer,the solar radiation intensity,the inclination angle of collector and inner diameter of copper tube and other parameters.The factors restrict each other.(3)Using the FLUENT software to establish the numerical model of a heating unit and to study the effect of various parameters on the thermal performance.Thereinto,the thickness of the glass,the thickness of the insulation layer,the ambient wind speed and the inclination angle have little influence on the performance of the collector.(4)In order to further improve the efficiency of collector simplify the structure of collector,this paper proposes a exhaust temperature in CPC capillary solar collector.The water inside copper tube is heated by concentrated of the CPC,the collector structure is simplified,and the influence of various parameters on the heating unit of thermal performance has been simulation analyzed.With the increase of radiation intensity,the thermalperformance of the collector is improved;Wind speed,the thickness of the glass,insulating layer thickness,inclination angle has little effect on the performance of the collector;with the increasing of the copper tube inner diameter,the heat collecting efficiency is significantly increased and the heat collecting performance improved dramatically.(5)Building a solar collector thermal performance test rig of PHP with CPC,an experimental study on the performance of collector has been carried on.The study found that working fluids,filling rate,collector inlet water temperature and ambient temperature have great influence on the performance of collector,inclination angle has little effect on the heat transferring performance;R134a has the best performance;filling ratio of 40% has better thermal performance and smaller thermal resistance than filling ratio of 60%;As the water temperature of the collector is rising,the heat efficiency decreases;The heating collecting efficiency was significantly decreased when the inlet water temperature of the collector reaches 45?;With the declining of the ambient temperature,the thermal resistance of the heat absorber of PHP is reduced,heat collecting efficiency is also reduced due to the heat loss increasing.A preliminary exploration research has carried on the medium temperature solar collector with CPC and PHP from two aspects of theory and experiment,which provides a certain research basis for the new type of solar collector and a train of thought for solar energy efficient and small scale of medium temperature heating.