Research On Influence Of Section Types Of Channel On Flow And Heat Transfer Characteristics In Solar Heat Absorber

Abstract:The flat-plate solar collector has got global attention for its high thermal efficiency,low price and facilitating to integrate with buildings.It takes account about90%share of solar collector market in the world with an exception of China.In our country,with the development of solar building integration process,the demand for flat-plate solar collector is also growing, solar heat absorber is the core component of the flat-plate solar collector,the cross section’s shape and the inner wall’s style of the solar heat absorber’s channel in which there is working fluid will produce a great influence on flow and heat thansfer characteristics of working fluid.This paper designs several different section types of channel,whose area of material section and flow section are all equal,and researches the influence of section types of channel on flow and heat transfer characteristics of working fluid,this will provide a theoretical reference for designing the channel of working fluid in solar heat absorber,the improvement of performance and structural optimization.The physical model for this study is established through abstracting and simplifying the actual model,and the geometric model of channel with two types is also established. In the theoretical analysis, mathematical model and theoretical formula involveing in the physical model are established.With the meshing of the geometric model, setting the initial and boundary conditions, the calculation of the numerical simulation is made.After finishing the calculation of the numerical simulation,this paper makes the analysis of velocity,temperature,heat transfer rate and pressure drop with the four types channel whose inner wall is smooth,the four types channel include single circle channel,single rectangle channel,several circles channel,several rectangles channel;moreover,a comparion between the three types single rectangle channel whose inner wall with different fin and the single rectangle channel whose inner wall is smooth is made, the different fins include semicircular fin,rectangle fin and triangle fin,the paper also make the analysis of velocity,temperature,heat transfer rate,pressure drop, skin friction coefficient, surface heat transfer coefficient and surface Nusselt number.The experimental platform of studying of flow and heat thansfer characteristics of working fluid is established,the experimental results are discussed and analyzed mainly from three aspects of temperature, pressure drop and velocity.A comparion between experimental results and simulation results is made,and the simulation results is verified. Eventually come to some rules of the influence of section types of channel on flow and heat thansfer characteristics of working fluid in solar heat absorber:from the view of heat transfer characteristics,if the channel’s area of material section and flow section are all equal,the several rectangles channel is the best of the four types channel whose inner wall is smooth,but the channels whose inner wall has fins are all better than the channels whose inner wall is smooth,and the channel with triangle fin is the best; from the view of flow characteristics, if the channel’s area of material section and flow section are all equal,the resistance loss of channels whose inner wall is smooth is all smaller than the resistance loss of channels with fins,and the single circle smooth channel’resistance loss is the minimum.