Research On The Application Of Airfoil Structure In Compact Heat Exchange Device

Airfoil is a classical structure in aerodynamics.Its unique flow pattern can significantly reduce pressure loss,and hence it has been receiving numerous attentions in the development of heat exchanger recently.In the present study,the main focuses were to explore the feasibility of applying airfoil structures in the design of heat exchanger under different scenarios.Through the comprehensive assessment of thermal-hydraulic performance and the characterization of local heat transfer mechanism,the influence of the installed airfoil structures in the flow channel on the heat transfer enhancement and pressure loss was discussed in detail.The effects of geometric parameters as well as the arrangement patterns of the airfoils on its comprehensive performance was carefully explored..Airfoil vortex generators(VGs)were firstly applied to enhance the heat transfer performance in a fin-and-tube heat exchanger.Numerical simulations were carried out to:(1)investigate the heat transfer and flow characteristics of VGs with different airfoil structures under different Reynolds numbers,and meanwhile the effects of VG height,angle of attack,relative positions and other geometric parameters;(2)characterize the enhanced heat transfer mechanisms of airfoil VGs by comparing the flow parameters and the comprehensive heat transfer factor,local Nusselt number and secondary flow intensity.Meanwhile,for fin-and-tube heat exchangers,redesigning the shape of tubes is another option to improve the overall performance.As a result,this study also investigated the thermalhydraulic performance of a new configuration of applying airfoil shaped tubes in a fin-and-tube heat exchanger.Based on numerical simulation:(1)The hydraulic,heat transfer and comprehensive heat transfer performances of different tube types such as circular,elliptical and airfoil tubes were studied;(2)The influence of the angle of attack as well as the arrangement of the airfoils on the flow and heat transfer performance were investigated in detail;(3)A more compact heat exchange channel structure design is proposed by systematically studying the arrangement of the airfoil tubes.Printed circuit board heat exchanger(PCHE)is a new type of compact heat exchanger.Its working temperature,pressure,and working medium are very different from other heat exchangers.As it is so compact,a reasonable fin structure is necessary to be optimized in order to reduce the system pressure loss.Therefore,this study further explores the thermal-hydraulic performance of airfoil fins in a PCHE.Based on the numerical simulations:(1)the flow resistance and heat transfer performance of NACA 0024 airfoil fins in the cold and hot channels under the same inlet mass flow rate were investigated;(2)Effects of the thickness,camber length,and angle of attack of a series of NACA airfoils on the heat transfer,flow resistance and overall performance of the PCHE heat exchange channel were explored;(3)The response surface method(RSM)of the central composite design(CCD)was used to correlate the convective heat transfer coefficient,the pressure drops of the cool/hot sides and the geometric design parameters,and the significance of the primary,quadratic and interaction terms of the design parameters in each response variable was clarified.