Influences Of Operational And Structural Parameters On The Performance Of Wavy Fin-and-tube Heat Exchangers

The condition of indoor thermal environment is mainly affected by temperature and relative humidity.The environment is too humid,which not only makes people feel sultry,but also breeds bacteria and affects human health.Most areas in the south of China are in areas with hot summers and cold winters or hot summers and warm winters.Even in the transition season,it is necessary to activate the air-conditioning dehumidification function in many areas in the south.The finned-tube heat exchanger plays an important cooling and dehumidifying role in the air conditioning system.Previous studies have focused on the effects of operating parameters and structural parameters on the performance of tubefin heat exchangers under specific inlet air conditions.The range of selected operating parameters and structural parameters is relatively narrow,and the inlet air conditions are not based on actual environmental parameters.As a basis,it is not enough to reveal the performance difference of heat exchangers when they are applied in different hot and humid environments,and it can not well guide the design of air-conditioning systems in different climate areas to the structural selection and operation optimization of heat exchangers.In addition,with the development of household central air-conditioning systems,the research of air-water finned tube heat exchangers needs to be more extensive and in-depth.To provide sufficient guidelines for optimizing operational parameters of wavy finned-tube heat exchanger under different thermal and moisture loads,a mathematical model was established to solve the heat transfer and dehumidification problem of a 9-row tube air-water counterflow wavy finned-tube heat exchanger.Resorting to Matlab programming,the model simulation results were validated by experimental data at first.Then,the effects of water flow speed,wind speed,inlet water temperature,transversal tube pitch,longitudinal tube pitch,and fin pitch on heat transfer and dehumidification performances of heat exchanger were explored under the weather conditions of Xi'an,Guangzhou and Hangzhou.Results show that adjusting wind speed has the greatest impact on heat exchange capacity,but adjusting inlet water temperature has the greatest impact on dehumidification capacity.When only the operational parameters are changed under the structural parameters of the experimental prototype(longitudinal tube pitch is 21.65 mm,transversal tube pitch is 25 mm,and fin pitch is 2.8mm),the heat exchange and dehumidification capacities in Guangzhou are 23.8%~44.1% and 33.5%~64.3% higher than those in Hangzhou,the heat exchange and dehumidification capacities in Guangzhou are 36.3%~83.3% and 117.8%~693.3% higher than those in Xi'an.And they almost don't vary with the change in wind speed,but increase linearly with the decrease in water temperature.When only the structural parameters are changed under rated operational conditions(wind speed is 2m / s,water speed is 1m / s,inlet water temperature is 7 ° C),the heat exchange and dehumidification capacities in Guangzhou are 23.2%~33.9% and 32.9%~47.3% higher than those in Hangzhou,the heat exchange and dehumidification capacities in Guangzhou are 25.5%~57.3% and 100.2%~213.4% higher than those in Xi'an.And they almost don't vary with the change in structural parameter.Under the coupling effect of structural and operational parameters,the heat exchange and dehumidification capacities in Guangzhou are 23.0%~44.3% and 32.5%~64.5% higher than those in Hangzhou,the heat exchange and dehumidification capacities in Guangzhou are 23.1%~87.7% and 94.7%~722.9% higher than those in Xi'an.The proper ranges of various operational parameters and structural parameter that should be taken to achieve the rated heat exchange capacity are proposed for operating in Xi'an,Guangzhou and Hangzhou.