Study On Heat Transfer Enhancement Of Fin-and-Tube Evaporator Based On Field Synergy Theory

Due to its good heat transfer effect,small size and other advantages,heat exchanger are widely used.Fin-and-tube heat exchanger as the most commonly used components in air conditioning systems,it plays an important and significant role in improving heat transfer efficiency for China's energy-saving emission reduction,and economic development.In this paper,the numerical simulation and experimental study on the dry and wet conditions of the heat exchanger are performed for by using the computational fluid dynamics method.The 3D model of plain fin,wavy fin and louver fin were established.And we add mass source and energy source phases during the steam condensation process by UDF to consummate the heat transfer and mass transfer process in the wet condition.And we study the heat transfer and fluid flow characteristic of plate fin-and tube heat exchanger under dry and wet conditions.In addition,the simulation results based on experimental results for feasibility analysis.The accuracy error was 6%-14%,which meet the accuracy requirements.Finally,according to the velocity and temperature synergetic distribution in the flow field,the structure is optimized to achieve the purpose of enhanced heat transfer.Since the heat transfer process of the fluid under the wet condition occurs phase change,the total heat transfer coefficient under the wet condition is far greater than the heat transfer coefficient under the dry condition.Under wet conditions,the Nu of plain fin is about 1.1 times than the dry condition,wavy fin is 1.21 times,and louver fin is 1.28 times;however the resistance coefficient under wet conditions is higher than the dry condition,the friction factor f of the louver fin is 1.56 times than the dry condition and wavy fin is 1.28 times.The plain fin is less affected by the dry and wet conditions,which is 1.08 times.And when the air flow through the copper tube,it occurred flow around a circular cylinder phenomenon.So there is a retention area in the leeward side,where the synergy is poor and the heat transfer capacity is weak.For louver fin and wavy fins,due to it increased disturbance to the fluid,the overall synergy is improved compared to the plain film,and the heat transfer effect is improved.Finally,it strengthen heat transfer for the region with poor synchronicity in the flow field and optimized fin structure.The j / f of the louver fin is 9.75% higher than plain fin,and the j / f of the bridge fin is 4.55% higher than the j / f of the louver fins.