Optimization Of Heat Transfer Characteristics To Downhole Air Cooler

With the improvement of mechanization level of mining,the mining depth is increasing and the heat damage phenomenon of high temperature,high humidity inside the mine is becoming more and more serious.As the most common terminal equipment of mine air conditioning,the performance of surface type air cooler is of great importance to solve the problem of mine heat damage.Therefore,it is an urgent problem to study the factors influencing the condensing heat transfer of mine air cooler,optimize the internal structure of air cooler and improve the condensing heat transfer performance of mine air cooler.In this paper,the condensing heat transfer of the external fluid in the pipe wall was analyzed theoretically.It established two model,one of single smooth tube and one of air cooler which include three rows of smooth circular tubes.The main research contents and conclusions are as follows:1)The influence of different pipe cross section shapes on condensation heat transfer was researched.The physical model of single smooth tube is established.And compare the situation of moist air condensation heat transfer on the wall surface of four types of heat exchange pipes with the same cross-sectional shapes(round pipe,#1elliptical pipe,#2elliptical pipe,#3elliptical pipe),and the results show that with the increase of the axial ratio of the ellipse tube,the heat and mass transfer coefficient showed an increasing trend on the whole,the moisture evolution coefficient also increased,and the proportion of latent heat transfer increased.The condensing heat transfer effect of the elliptic tube is better than that of the circular tube.2)Based on the numerical model of condensing heat transfer of air cooler with three rows of smooth tubes,the influence of parameters such as inlet velocity,inlet temperature and pipeline wall temperature on the condensing heat transfer effect of air cooler was analyzed by using the control variable method.The results show that the increase of inlet velocity,temperature and wall temperature improved the mass transfer rate of moist air.The condensed water decreases with the increase of air velocity and increases with the increase of air inlet temperature and wall temperature.The cooling effect of air decreases with the increase of steam velocity and wall temperature,and increases with the increase of inlet temperature.The coefficient of heat and mass transfer increases with the increase of inlet velocity and inlet temperature,and decreases with the increase of wall temperature.3)Based on the numerical model of condensing heat transfer of air cooler with three rows of smooth tubes,the structure of air cooler is optimized.The influence of different structure parameters such as sequential and cross arrangement modes,relative position relationships was analyzed.By comparing the influence of two arrangement modes on the condensation heat transfer of moist air in the air cooler,it is found that cross arrangement mode is the best.By comparing the condensation heat transfer of moist air in air cooler with different relative position relationships(tube spacing of 30 mm,35mm,40 mm,45mm,50 mm,respectively),the optimal tube bundle spacing is 40 mm when the hydraulic diameter is 20 mm.