Theoretical And Experimental Research On Heat Exchange Performance Of Air-cooled Evaporative Compound Type Cross-flow Closed Cooling Tower

As an important heat exchange equipment in the industrial field,cooling tower is widely used in all walks of life.The air-cooled cooling tower uses the temperature difference between the surrounding air and the cooling water to cool the cooling water;the evaporative cooling tower uses the unsaturation of the air,driven by the water vapor partial pressure difference.So that the cooling water in the open cooling tower exchanges heat and mass,and the spray water in the closed cooling tower exchanges heat and mass with the air.No matter what kind of cooling tower,the core medium of heat exchange is water.However,China is in short supply of water resources,unevenly distributed between the north and the south.The industrial water consumption is huge.Therefore,it is necessary to study water-saving cooling towers.The series air-cooled evaporative composite cross-flow closed cooling tower studied in this paper was a typical water-saving cooling tower.Due to the addition of finned tubes,the cooling tower had both air cooling and evaporative cooling.It can greatly save spray water.In addition,the composite cooling tower had a variety of operating modes.Choosing different operating modes according to different climatic conditions can meet the cooling requirements while avoiding energy waste.This paper used a combination of numerical simulation and experimental research to study the structure and operating parameters of the composite cooling tower,and combined the composite cooling tower with the group intelligence algorithm to determine the structural parameters of the composite cooling tower.The structural parameters of the composite cooling tower were optimized to some extent,and the applicability of the optimized cooling tower in different regions of China was discussed.In terms of numerical simulation,the mathematical model of the air-cooled evaporative composite cross-flow closed cooling tower was established,and two structural forms of the composite cooling tower were proposed(the finned tube area is on the top,the smooth tube area is on the middle,the filler area is on the bottom and the finned tube area is on the top,the filler area is on the middle,the smooth tube is on the bottom).The corresponding programs were compiled for these two tower types using Matlab software.Taking tower type one as an example,the influence of some structural parameters on the composite cooling tower was studied.Studies had shown that:with the increase of fin height,fin tube wall thickness,and coil inner diameter,the efficiency of the cooling tower increases;with the increase of fin spacing,fin thickness,and smooth tube wall thickness,the efficiency of the cooling tower decreases.As far as the degree of influence was concerned,the change of the fin height and the inner diameter of the coil has a greater influence on the cooling efficiency.while the thickness of the fin and the wall thickness of the coil had a smaller influence on the cooling efficiencyIn terms of experimental research,the two tower types under different operating parameters were studied,and the heat exchange between finned tubes and bare tubes were analyzed separately.The results show that the change of operating parameters had the same effect on the two tower types.With the increase of cooling water flow and spray water flow,the heat exchange of the finned tube and the heat exchange of the bare tube increased,the total heat exchange of the cooling tower increased,and the cooling efficiency improved;with the increase of air flow and air-water ratio,the heat exchange of the fin tube increased,but the heat exchange of the bare tube decreased,and the total heat exchange of the cooling tower increased,the cooling efficiency improved.Compared with tower type 1,tower type 2 had better cooling performance.The cooling efficiency of tower type 2 was 3%～8%higher than tower type 1 under the same conditions.In terms of structural optimization,taking tower type 2 as an example,using Matlab to combine the particle swarm algorithm with the mathematical model of the composite cooling tower,12 structural parameters in the composite cooling tower were optimized,and the composite cooling tower with the highest cooling efficiency was obtained.Several combinations of cooling tower structural parameters,and screening them from two aspects of size and initial investment,and finally determine the structural parameters of the cooling tower.The optimized cooling towers were applied to five climatic regions in China.The results show that the cooling tower studied in this paper was more suitable for hot summer and cold winter regions or hot summer and warm winter regionsThis article aims to explore the influence of different parameters on the composite cooling tower,find the cooling tower structure and structural parameters that are most conducive to the cooling performance,and explore the applicability of the composite cooling tower in China.It is expected to provide a basis for the application of the series air-cooled evaporative composite cross-flow closed cooling tower in the project promotion and application.