Numerical Simulation And Experimental Research On Heat Transfer Flow Characteristics Of Asymmetric Plate Heat Exchangers

The asymmetric plate heat exchanger is a new type of plate heat exchangers,which can reduce heat exchange area under many working conditions,showing a good application prospect.However,due to the diversity of its structure and the uncertainty of its application range,its application in the market is limited.Therefore,it is of great significance to study its overall resistance and heat transfer performance to get its suitable application range.In this paper,the flow and heat transfer performance of asymmetric plate heat exchangers with different ripple heights were studied by numerical simulaiton.The influence of ripple depth on thier performance was analyzed.The asymmetric plate heat exchangers were also compared with a symmetric plate heat exchanger.Detailed research results were as follows:1.The asymmetrical plate heat exchanger was experimentally studied by using the experimental device of plate heat exchanger.The temperature and pressure drop in the inlet and outlet of the fluid were obtained.The heat transfer criterion equation of the experimental plate heat exchanger was fitted and compared with simulation results.The deviation of Nusselt number between simulation and experiments was less than8.0%,and the deviation of pressure drop between simulation and experiments was less than 8.2%,which could verify the numerical model.2.The performance comparison of the asymmetric plate exchange,which ratio of high corrugated depth to low corrugated depth was 2,and symmetrical plate exchange was simulated in different flow rate ratio of hot water to cold water and different allowable pressure drops.The heat transfer coefficient of asymmetric plate heat exchanger would increase more than 10% compared to the symmetric plate exchange when the flow rate ratio was greater than 1.3:1.When the allowable pressure drop increases from 16 k Pa/m to 80 k Pa/m,the heat transfer coefficient increasing percentage of asymmetric plate heat exchanger could be up to 30%.The number of contact points in the narrow channel and wide channels were different may be the reason of this phenomenon.3.The asymmetric index N was proposed to describe the ripple depth of asymmetric plate heat exchangers.The effect of asymmetric index on heat transfer performance was analyzed.The Nusselt number and friction coefficient formulas including asymmetry index were fitted.With the decreasing of N value,the difference of performance evaluation index ?=Nu/f^1/3 between the two channels of asymmetric plate was gradually increased.4.The sensitivity of asymmetric plate exchangers to operating conditions used in water-water heat transfer was studied.And the suitable working conditions of different asymmetric plate heat exchangers compared to the symmetric plate heat exchanger were obtained.