Study On Flow And Heat Transfer Characteristics Of Air Side Divergent Heat Transfer Surface Without Thermal Contact Resistance

Heat exchanger is one of the most important part of energy and power industry and its performances of flow and heat transfer has a direct impact on the related systems.Because of the air side heat transfer has great influence on the performance of overall heat exchanger and based on heat transfer component without thermal contact resistance,a new air side divergent heat transfer component without thermal contact resistance is proposed,and in this thesis we study its flow and heat transfer performance by numerical calculation and experimental tests.In this thesis,we study the three basic heat transfer process of air side divergent heat transfer component without thermal contact resistance by theoretical analysis.According to the traditional heat transfer model,we conclude a suitable method,which can be applied to analyze the three heat transfer process of air side divergent heat transfer component without thermal contact resistance.The three heat transfer process are water side convective,fin heat conduction and air side convective.The heat transfer model of air side divergent heat transfer component without thermal contact resistance is reasonably simplified,and we use 3D modeling software,Proe,to establish the calculation model.Then use Gambit to complete the grid division of the computational model,and the grid is structural grid.After that,use fluid-solid coupled heat transfer model and k-? turbulence model for flow and heat transfer process numerical calculation.According to the numerical results,we analyze the air side convection heat transfer and flow resistance of different equivalence Re,obtain the temperature distribution of fin thermal process and analyze the heat transfer performance of water side convection.The results of numerical calculation is verified with the standard laboratory experimental correlation.We conclude the correlation formula of air side Nu on the Re.Finally briefly analyze the flow and heat transfer characteristics of different air side divergent angle of air side divergent type heat exchanger elements,and we can find that the air side Nu increases with the increase of Re.At the same time,because of the local resistance of inlet,the overall flow resistance also increases with the increase of Re.The heat transfer performance of air side divergent heat transfer component is better than the air side uniform heat transfer,and the ratio is between 2.4~4%,but at the same time flow resistance significantly increase.Finally,set up a small wind tunnel test station for measuring the flow and heat transfer performance of air side heat exchanger element diverging,and make two experimental samples by wire cutting processing technology.One is air side divergent type experimental element,the other is a experimental element with rectangular fins.Through constant power heating,use the centrifugal fan to change the air flow rate,measuring the flow and heat transfer performance of the experimental element.Based on a large number of experimental data,we conclude the air side convective heat transfer properties of the air side divergent heat exchanger and the pressure resistance during the air flow process,and based on experimental data,we analyze the sources of numerical calculation.