Effect Of Baffle Layout On The Performance Of Solar Air Collector

As the key equipment to gather solar radiation energy,solar air collector(SAC)is an indispensable part of solar thermal conversion process.Due to the heat conductivity coefficient,density and specific heat of air is small,as the heat-transfer medium of SAC,there is a low heat transfer rate between the absorber plate and air.The accumulated heat increases the temperature of absorber plate,which will increase the heat loss and limit the application scope of SAC.In order to further improve the heat collecting efficiency of SAC,numerous novel ideas have been put forward by domestic and foreign scholars to improve the thermal performance of SAC.The type SAC with the introduction of suitable baffles in the collector is a typical optimization method.On the basis of Baffle-type SAC(BSAC),this paper put forwards a new optimization method of “rearrange the baffle layout with the first-cavity narrowing”.The mechanism of enhanced heat performance by first-cavity narrowing is revealed by analyzing the flow and heat transfer characteristics of the five first-cavity narrowing models.The results show that narrowing the first cavity can improve the heat collecting efficiency obviously,and change the resistance of BSAC weakly.At the same time,there is an optimal narrowing width for a certain scale BSAC.In the scope of this paper,the optimal width of the first cavity is 200 mm and the maximum growth rate is 16.90% comparing with the baffle uniform distribution model.Based on the first cavity width of 200 mm,the models were established with changing the baffle layout of the last four chambers.The results show that widening the tail cavity width can result in the increase of high temperature area and heat loss of the tail cavity,and narrowing the width of the tail cavity can result in the increase of flow resistance and heat loss of the middle chambers.Therefore,the change of the baffle plate layout in the last four chambers cannot improve the thermal performance significantly.According to the optimal model of numerical simulation,the experiment table was established according to the ratio of 1:0.5 to verify the correctness of the first-cavity narrowing method.The experimental results are consistent with the numerical simulationresults,which verifies the correctness of the numerical simulation results.The experimental results also show that the first-cavity narrowing method can get better results under low speed,and the heat collecting efficiency is not sensitive to the heating power of absorber plate.The first-cavity narrowing method has a stable optimization effect and is suitable for promotion to different application fields and different climate regions.This paper provides a new idea to optimize the thermal performance of BSAC.