Numerical Study On Heat And Mass Transfer Of Moist Air Flowing Through Plane Finned Tube Surface

Nowadays, on many occasions of production and chemistry, the heat exchanger is needed to transfer the heat between cold and hot fluid. The plain finned tube heat exchanger, with its simple structure and small pressure drop loss, has been widely used in the field of air conditioning refrigeration. In the context of the current energy shortage, it is necessary to further strengthen the effect of heat-exchanging on the air side of the fin, making the heat exchanger more compact, high-efficient and energy-saving. Since the researchers have given different results of the value range of Lewis factor in the process of heat mass analogy, it is needed to find out a range suitable for plain fin under dehumidifying conditions. Based on this, the research in this paper is of great scientific value and practical significance.This paper studies the heat and mass transfer between moist air and plain finned tube heat exchanger under dehumidifying conditions. Due to the complexity of heat and mass transfer in the phase change process, the experimental method cannot result an overall distribution of the temperature and velocity in the flow field. So this research adopt a numerical method.In this research, a reasonable assumption of the heat transfer when the humid air flows through the plain finned tube heat exchanger is made. A numerical model of the heat and mass transfer is established on the air side of fins, the rationality and feasibility of the model are verified. FLUENT software is applied to solve the established numerical model. The objects are the phase-change heat transfer of 2～5 rows of finned tube heat exchanger when the moist air inlet velocity is in the 1～6 m/s range and its relative humidity in the 30%～100% range. We analyze the influence of inlet moist air parameter and heat exchanger tube row number on the quantity and coefficient of heat and mass transfer, analogy analysis of heat and mass transfer,and fin performance.The results show that when the fin surface is under partly dehumidifying conditions, non-condensed area in front of the tube row increases with the increase of inlet air velocity while the non-condensed area at the back of the tube row decreases. The total condensation amount and heat transfer rate on the fin surface increase with the increase of the flow rate of the moist air inlet, relative humidity, and the tube row number of the heat exchanger. The heat transfer rate and condensation amount of each tube row near the moist air inlet are greater than that of the downstream areas. When the moist air inlet velocity is greater than a certain value, the condensation quantity of the second row tube will be close to that of the first row tube. In this paper, the research scope of Lef values is between 0.9～1.01. The heat and mass transfer fin efficiency decrease with the increase of moist air inlet velocity and increase with the row number. When the inlet relative humidity increases, the fin efficiency of heat transfer drops and that of the mass transfer increases.