Numerical And Optimization Research On Conjugated Heat-transfer Performance Of Plate Heat Exchanger With Dimples And/or Protrusions

The metal plate is the main part of the plate heat exchanger. The heat transfer and momentum conversion is determined by the shape of surface. The heat transfer and flow resistance characteristics in the double flow channel of plate heat exchanger with dimples are numerically studied by conjugate heat transfer method based on the principle of enhancement of heat transfer. And a new kind of wavy plate heat exchanger is proposed. The main work and conclusions of this paper are as follow:(1) The plate heat exchanger with dimples and smooth plate are numerically studied by conjugate heat transfer method. The Standard k-? model and Enhanced Wall Function are applied in caculation. The nitrogen is the working medium in the hot side and the helium is the working medium in the cool side. The whole flow channel of plate heat exchanger with dimples and smooth plate heat exchanger are investigated. The results show that the total heat transfer, the surface coefficient of heat transfer and Nu increase with the Re increases, meanwhile f decreases gradually with Re increases. The comprehensive heat transfer performance Nus/fs^1/3increases with Re increases and it varies from 246 to 566. The synergy angle in the dimples decreases sharply, it indicates that the dimples is conducive to improve the synergy performance of temperature field and flow field.(2) The multi-objective optimization research on structural parameters and fluid parameters of double channel of the plate heat echanger with dimples is studied.The simulation optimization is comprehensively consider the optimal structure parameters of the plate heat exchanger under different Re by using genetic algorithm and determining the constraints of the optimization objective and variables space in the Workbench platform. The results show that the prediction of response surface has reasonable value with the test results, and the optimization results are accurate and reliable. The depth of dimples h and plate spacing H have decisive effect to the objective function, the radius of dimples R has the second place, and the effects of dimples space P can be neglected. The flow and heat transfer equation of plate heatexchanger with dimples are obtained by multivariate linear regression analysis of125 groups of data.(3) A new kind of wavy plate heat exchanger has been proposed, and the heat transfer and flow resistance characteristics are numerically studied, which is based on the results of numerical simulation and calculation. The thermal performance of wavy plate heat exchanger is comparatively researched with smooth plate heat exchanger and plate heat exchanger with dimples. The influence of coupled heat transfer is analyzed with different structure parameters and flow conditions. The results show that the heat transfer performance of wavy plate heat exchanger slightly increases compared with the plate heat exchanger with dimples, but the increment decreases with Re increases. The f of wavy plate heat exchanger significantly declined compared with the plate heat exchanger with dimples. Comprehensive heat transfer performance of the wavy plate heat exchanger is much better than the smooth plate heat exchanger and the plate heat exchanger with dimples. The Re is the most sensitive parameters, followed by shear wavelength L, the amplitude h has no significant influence on Nu, f, and the comprehensive heat transfer performance.