Research On Experiment, Simulation And Application Of The Evaporative Cooling Heat Exchanger

The air conditioning and heating system consumes more than half of the buildingenergy. Improving the efficiency of air conditioning system through developingefficient equipments are important means of energy-saving and emission reduction.Evaporative cooling is considered as a high-efficiency cooling method, with advantagessuch as energy saving, compact structure, and has a great practical applicability in airconditioning system. Therefore, researching on its heat and mass transfer characteristicsand optimizing its parameters and structure will provide a theoretical support fordeveloping evaporative cooling heat exchanger technology and promote practicalapplication in engineering.The heat and mass transfer process of the evaporative cooling heat exchanger isquite complicated due to the diversity of fluid, structure and flowing direction. As aresult, the current research mainly focuses on the evaporative cooling heat exchangerwith specific configuration. There is lack of a general modeling for performanceanalysis and configuration optimization of different evaporative cooling heat exchanger.At the same time, the performance of the widely-used tube-and-fin evaporative coolingheat exchanger is not deeply investigated. To solve problems above, a series researchare conducted in this paper:(1) An experimental bench of the tube-and-fin evaporative cooling heat exchangerwas built. The effects of the parameters of air and cooled medium on the performance oftube-and-fin heat exchanger were investigated, and finally the mass transfer coefficientof the evaporative cooling heat exchanger was fitted based on experimental data.(2) A general modeling approach for complex evaporative cooling heat exchangerbased on spatial scanning was proposed. This method divides the evaporative coolingheat exchanger into a number of nodes, and each node is regarded as an independentmicro heat exchanger. The fluid flow is used to establish links between nodes and nodes,and the scanning iteration method is built to solve the energy conservation equationsbetween different nodes. The method was validated by the experimental results.(3)The built model was used to analyze the parameter distribution and impact ofthe fluid inlet state on the evaporative cooling heat transfer. And the model was alsoused to optimize the configuration of different type evaporative heat exchanger, which can be used to guide the enhancement of the evaporative heat exchanger.(4) Mathematical model of the tube-and-fin air conditioner was established, and thevariable condition features of the air conditioner with and without spray were analyzedand compared. The results showed that the cooling seasonal energy consumption of theunit with spray decreased20%~26%. According to manufacturer experimental data, aircooling, water cooling and evaporative cooling chiller performance model were built,and the SEER of three kinds of chiller were compared. As a result, the SEER of theevaporative cooling chiller is13%~30%higher than air cooled chiller and2%~11%higher than water cooled chiller. This research will largely help the research anddevelopment of the evaporative cooling chiller and design of the HVAC system.