Numerical Simulation Of Thermal Plume Backmixing In Cooling Tower Group

As an important part of the central air conditioning system,the cooling effect of cooling tower directly influences the operation performance of the central air-conditioning system.Due to the limitation of installation position of air conditioning cooling tower,the thermal plume backmixing has a negative effect on the energy consumption of the cooling tower.For the above problems,the numerical simulation method is used to study the thermal plume backmixing in the air conditioning cooling tower group.The conclusions are as follows:The outdoor cooling tower group with forced ventilation under a row of obstacles was taken as the research object,the law of heat and moisture of cooling towers has been investigated using the continuity,momentum,energy and component mass conservation equations.The average moisture fraction and average backmixing rate of air inlet were used as evaluation indexes.The influence of the height of obstacle,the distance between the obstacle and the cooling tower and air guide on the heat and moisture transfer of the air flow in the cooling tower has been studied.The results show that:(1)When the obstacle lies in the back of the cooling tower,the distance between the obstacle and the cooling tower is small,the average moisture fraction and average backmixing rate of the cooling tower increase with the increase of the obstacle height without air-guide.When the distance between the obstacle and the cooling tower is small,the average moisture fraction and average backmixing rate of air inlet change slowly with air-guide.(2)When the obstacle lies in the back of the cooling tower,no matter whether the cooling tower has air duct or not,the cooling tower exhaust has no effect on the average moisture fraction and average backmixing rate in the front part of the cooling tower,while the average moisture fraction and the average backmixing rate in the rear part of the cooling tower increase with the increase of obstacle height.When the obstacle lies in both sides of the cooling tower,the average moisture fraction and the average backmixing rate in the front of the cooling tower are larger than that in the rear area of the cooling tower.Air conditioning cooling tower group in the high-rise building equipment layer was taken as the research object,the air distribution around the cooling tower group has been investigated.The results show that the thermal plume backmixing of cooling tower is very serious,the average backmixing rate is about 20%,the average moisture fraction of the inlet is higher than that of the atmosphere moisture fraction 0.0177.Due to the failure of the hot and humid air to be discharged in time,the hot and humid air has a negative effect on the cooling effect of the cooling tower.Combined with the numerical simulation results in third chapter,the ventilation scheme of the air conditioning cooling tower was improved and an organized ventilation scheme was adopted to obtain the air distribution in the equipment layer under the scheme.Compared with the original ventilation scheme,the hot and humid environment at high temperature in equipment layer has been effectively improved.The average moisture fraction of the inlet is similar to that of atmosphere,the average backmixing rate of the cooling tower is about 2%.The return rate of hot humid air is reduced,the cooling efficiency of the cooling tower was improved and the normal operation of the central air conditioning system is ensured.The research results reveal the law of heat and moisture transfer in air conditioning cooling towers at high-rise buildings,which has a certain engineering significance on the governance of air conditioning cooling towers of thermal plume backmixing and the installation of air conditioning cooling tower.