Structure Design And Performance Analysis Of Composite Flow Closed Cooling Tower With Packing

Composite flow closed cooling tower with packing refers to both counter current heat exchange and cross current heat exchange in the cooling tower.Spray water and air are counter-current heat exchange in the coil area.After the temperature rise in the coil area,the spray water falls into the packing area and cross-flow heat exchanges with the air.Compared with traditional closed cooling tower with single coil,composite flow closed cooling tower is a closed cooling tower with packing and coil.It has lower manufacturing costs than closed cooling tower with single coil with the same cooling effect.Compared with the cross-flow closed cooling tower,spray water and air are counter-current heat exchange in the coil area,the heat exchange effect is better than cross-flow heat exchange,that is,in the case of the same coil arrangement,the counter-current can be obtained lower export cooling water temperature.Based on the above considerations,the feasibility of composite flow closed cooling tower with packing was determined,and the structural design,software development,and performance analysis were completed.Firstly,based on the heat and mass transfer theory,the heat and moisture exchange model of the coil area and the packing area was established on the basis of certain assumptions,and the analytical solution was obtained based on the empirical formula.Then the structure design process is converted into computer language,and the software development is completed to make it an independently executable software.The user can quickly obtain the size of the coils and packing in the closed cooling tower of the composite flow by inputting some determined parameters.Finally,the author conducted a performance analysis of the composite flow cooling tower with a certain structure.When designing the structure,the design conditions are standard conditions that the dry bulb temperature is 31.5?and the wet bulb temperature is 28?.The cooling water volume is250 m~3/h,the cooling water inlet temperature is 45?,and the outlet water temperature is 35?.The design process is to determine the size of the coil first,and then determine the packing size based on the temperature rise of the spray water and the amount of spray water.Whether in the calculation of the coil size or the packing size,there is a hypothetical value.The calculation method of the author is based on the hypothetical value to determine the size of the coil or the size of the packing,and verify whether the assumed value is consistent with the actual value.If the two values match,that is,the design is reasonable and does not match,the actual value is used instead of the hypothetical value to recalculate.After a few iteration cycles,the final output result will be obtained.Because the structure of the counter and cross in composite flow cooling tower in this project is symmetrical,half of the data is used in the design calculation,software development and performance analysis,and the other half structure is mirrored.Prior to the structural design,the user should specify the design task,the meteorological conditions of the cooling tower application,the type of packing and the other parameters.In the calculation,there is a case where the proper size cannot be obtained under the set conditions.For this moment,the author takes the adjustment of the air flow or the spray density,so the final result may differ from the setting valuer.All user should be understand this illustrate.The specific flow chart can be viewed in Chapter III.The final performance analysis was carried out on the premise of a fixed cooling tower structure.First of all,compare it with a composite cooling tower with pure counterflow.It is concluded that composite flow closed cooling tower has a slightly higher cooling water outlet temperature,but the resistance of the coil and the packing to the air is smaller.The influence of spray density and cooling water on the counter and cross in composite flow cooling tower was analyzed.With the spray density increases,the water temperature at the outlet of the cooling water decreases,the cooling efficiency increases,and the fan loss in the coil area increases.With the increase of cooling water,the cooling efficiency is reduced.The cooling water volume of the cooling tower structure designed in this project is recommended to be between 198m~3/hand 330m~3/h.