Study On Resistance Characteristics Of Low Reynolds Number Pulsating Flow In Flexible Mini-channel

As a kind of efficient heat exchange equipment,heat exchanger has a wide range of applications in the fields of HVAC,chemical industry,shipbuilding,metallurgy,etc.Therefore,improving the heat exchange efficiency of heat exchanger and reducing the flow resistance of fluids in heat exchanger are about the two unchanging topics of the heat exchanger.At present,there are more and more methods for reducing the flow resistance of fluids in heat exchanger with mini-channel,which can be mainly divided into active control drag reduction technology and passive control drag reduction technology,flexible wall drag reduction technology,without the need to input additional energy,has been widely concerned by scholars at home and abroad,but now the flexible wall reduction based on bionics is mostly used in the field of external flow fields such as ships and airplanes,and There are few studies on the internal flow field problem of flexible wall drag reduction technology such as heat exchanger.In this paper,the flexible wall drag reduction technology is applied to the in-flow pulsating flow,and the pulsating flow in triangular channel is taken as the research object.The characteristic of triangular mini-channel with flexible wall(hereinafter referred to as the flexible mini-channel)is studied.Firstly,in order to meet the experimental requirements,a flexible mini-channel was first designed,and the fourlevel five-factor orthogonal test was used to obtain the significance of the influence of the pulsation parameters and the flexible wall parameters on the flow resistance characteristics.Secondly,based on the bidirectional Fluid-Structure Interaction method,through COMSOL Multiphysics simulation software numerically simulates the resistance variation law and flow mechanism of low Reynolds number pulsating flow in flexible mini-channels.Based on above,the results of this paper are as follows:1.From the experiment on resistance characteristics of low Reynolds number pulsating flow in flexible mini-channel and the four-level five-factor orthogonal test analysis,it can be concluded that the five design factors include the pulsating average Reynolds number,the pulsation amplitude of pulsating flow,the pulsation frequency of pulsating flow and the type of wall material of the flexible mini-channel and the thickness of the flexible wall,and the average Reynolds number of the pulsating flow,the type of the flexible mini-channel wall material,and the pulsation amplitude of pulsating flow have a great influence on the flow resistance,The pulsation frequency has the least effect on the flow resistance.2.From the numerical simulation of two-way Fluid-Structure Interaction(FSI)of pulsating flow in a flexible mini-channel,it can be concluded that within the range of simulated parameters,the flow resistance increases with the increase of the average flow Reynolds number,pulsation amplitude and flexible wall thickness;the more flexible the wall,the flow resistance is smaller,The feasibility of flexible wall drag reduction technology in heat exchanger is verified;by the pulsation amplitude increases,and the flow resistance first increases and then decreases.Finally,the characteristics of the low Reynolds number pulsation flow resistance in the flexible mini-channel are explained from the difference between the deformation of the flexible wall surface and the stress of the flexible wall surface and the boundary layer velocity.Finally,through the dimensionless analysis,a correlation equation of the pulsating flow resistance factor in a flexible mini-channel is fitted.3.Through the orthogonal analysis of the experimental data and the two-way Fluid-Structure Interaction(FSI)numerical simulation experiment,it is verified that the flexible wall instead of the rigid wall has the effect of reducing the flow resistance of the pulsating flow heat exchanger.