Study On The Thermal Performance Of Packing In The Closed Counterflow Cooling Tower

Closed cooling tower will have more and more advantages in the metallurgy, electricity,chemical industry,food industry and many other applications.All along, the cooling tower packing is the core of open cooling tower and its thermal performance has a direct impact on the operating efficiency of the open cooling tower.In the counterflow closed cooling towers,the cooling tower packing has a cooling effect on the spilled water.There have been lots of study on the thermal performance of cooling tower packing at home and abroad,but the analysis study often pay attention on cooling tower packing itself,neglecting its real working environment. In particular the closed counterflow cooling tower,its structure and working principle are different from open cooling towers.Unlike open-cooling tower,the air works in the packing is not the atmosphere yet,because it has already flown through the coil area,Its state is different to the atmosphere.The water works in the packing is not the cooling water,but the cycled spray water.The heat of cooling water is distributed into the air through coil area and the cooling tower packing,the heat dissipation of the packing just oen part of the whole tower's heat dissipation.An in-depth on the thermal performance of packing in the closed counterflow cooling cower has an important reference value on the development of new products.In the closed counterflow cooling tower packing,the quality and heat exchange process of spray water and air obeys material and energy conservation law.On this basis,this article made reference to some literatures,considering the calculation of the efficiency-transfer units(ε—NTU) used in the heat exchangers,the author compile a mathematical calculation and use the MATLAB software to solve the mathematical model.It can calculate the temperature of outlet spray water and the enthalpy of outlet air by entering the parameters of the original variables,then calculate the temperature of outlet air.The maximum deviation of outlet spray water temperature measurements and calculated is 0.91%,the maximum deviation of outlet air temperature measurements and calculated is 0.72%.It verifies that the mathematical model is reasonable and the results meet the requirements of the project.In order to carry out experimental research,the author build a new type of closed counterflow cooling tower testing system in a company.The thermal Performance of cooling tower packing has been stuied when spray water and air flow changes.Experimental studies have show that,while the cooling water flow.cooling water inlet temperature,the import air fow,the import air status unchanged,with the increase of the ratio of air to water,spray water temperature difference gradually increased,pray water heat dissipation gradually reduce,the percentage of the load of closed counterflow cooling tower accounted for pray water heat dissipation increase firstly and then decrease,the efficiency of closed counterflow cooling tower gradual reduce.While the cooling water flow,cooling water inlet temperature,spray water flow and the import air status unchanged,with the increase of the ratio of air to water, spray water temperature difference and pray water heat dissipation increased firstly and then decrease,the percentage of the load of closed counterflow cooling tower accounted for pray water heat dissipation increased firstly and then decrease too,the efficiency of closed counterflow cooling tower gradual increase.When the counterflow closed cooling towers have reached the required efficiency standards,the percentage of the load of closed counterflow cooling tower accounted for pray water heat dissipation is very low,This shows that Cooling water heat dissipation already gone into the air in coil region.In this experiment,when the cooling water flow is 9.00t/h,the air flow on the unit cross-sectional area of cooling tower packing is 3.46(kg/m~2.s),spray water density is 3.50(kg/m~2.s),the ratio of air to water is 0.99,the efficiency of the closed counterflow cooling tower get the highest value,it is 95.93%.In this condition,the heat dissipation of cooling tower packing is 3.37kW,the heat dissipation of the closed counterflow cooling tower is 69.05 kW,the percentage of the load of closed counterflow cooling tower accounted for pray water heat dissipation is 5.18%.