Research On The Flow And Heat Transfer Characteristics Of Air-water Plate Heat Exchanger

With the development of society economy and technology, demand of energy resources grew day by day. Under the condition of limited energy resources, enhanced heat transfer, efficient and energy-saving technologies, product applications had been paid a great deal of attention. The study of the process of enhanced heat transfer technology and designing the novel compact heat exchanger devices had became an important problem with theoretical and practical meaning.The main contents of this paper were the studying of air-water medium corrugated plate heat exchanger flow resistance characteristics according to the principle of primary surface heat transfer. The two successful cases of plate heat exchanger and gas turbine regenerator which applied primary surface to transfer heat efficiently were extensively researched including theory study, experiment study, numerical simulation and model development. Then the efficiently primary surface was introduced to the field of air-water heat transfer, which expanded the application scope of primary surface.The traditional water-water plate heat exchanger was converted into air-water heat exchanger and the experimentation was carried out. Through comparing with the heat transfer and flow resistance authority data of smooth tube and finned tube compact heat exchangers, the results demonstrated that the primary surface corrugated plate heat exchanger had the characteristics of low flow resistance and compact construction and could transfer heat efficiently between water and air.The salient and depression of the primary surface corrugated plates were not only the promotion of passive disturbance, but also could block the development of boundary layer. The corrugated plates with inclination angle were congruently placed; the flow passage had a complex space structure. In view of these characteristics, the basic laws-the mass conservation, momentum conservation, energy conservation and the basic theory of turbulence were adopted in the study to establish the mathematical model of air flowing and transferring heat between the corrugated plates. Through solving 27 physical models which could represent the shape and surface characteristics of the primary surface, the impact of air transferring heat and flowing between the corrugated plates by corrugation shape, corrugation height and corrugation inclination angle were compared. The indexes of high convective heat transfer coefficient and low flow resistance were selected and several efficient primary surfaces were primarily chosen. The area best heat transfer factor j/f and volume best heat transfer factor E were taken as the follow-up estimation basis to select the best one.The method of differ height corrugation was put forward innovatively on the basis of differ section theory. The experimentation proved that this method could reduce the heat capacity ratio of the fluid on both sides further and improved the heat transfer efficiency. The numerical simulation data and experimental results were compared and the mathematical model was validated satisfying the request of this study.The anti-frozen performance of stainless steel corrugated plates was also experimented studied. The minimum icing temperature of water on the stainless steel surface was determined; the convex-concave structure could block the ice adhering on the surface of corrugated plates and had a certain anti-frozen function. The three-dimensional processes of water statically freezing and flow freezing between the corrugated plates were simulated; the temperature variation and phase change interface moving law were analyzed, which could be used in the improvement of corrugated plates.This study provided the basis and method guidance to the design and development of air-water primary surface and similarly the compact, efficient heat exchange equipment, which expanded the scope of application and had a certain theoretical and practical value.