The Optimization Design And Software Development Of The Closed Cooling Tower Composed With Air And Evaporation Cooling

The closed cooling tower composed with air-cooling and evaporative cooling is a heat exchange equipment which put the finned tubes and plain tubes in a series. Cooling water and air transfer heat through the coil, not only ensure the water quality of cooling water is not contaminated, but also reduce the evaporation of water waste, improve the reuse rate of water. Cooling water firstly flow through the finned tubes,and then flow into the evaporative cooling plain tubes, when the cooling water is cooled to a certain temperature it flow out of the tower. The composite closed cooling tower has two sets of running programs, one is a combination of air cooling and evaporative cooling operation when the outdoor air temperature is high,which can not be achieved simply by air cooling to achieve the cooling demand;another running program is to close the spray water,reducing the temperature of cooling water only relying on the air cooling,when the outdoor air dry bulb temperature is low,this kind operation scheme can save energy consumption of spray water and spray pump.Based on the study of the theory of traditional cooling tower,this thesis studies mainly from three aspects:establishing and solving the mathematical model,developing the design software and optimizating the structure and operation parameters.Firstly,based on the heat and mass transfer theory, the heat transfer process of finned tubes and plain tubes has been analyzed, and due to the different heat transfer conditions in two parts, the mathematical models are established respectively. According to the empirical formula, heat and mass transfer coefficients have been obtained,and the analytical solution under certain assumptions is gotten,finally we get the designed results of the tower.Secondly, the design process of the cooling tower is converted into computer language, with the Visual Basic programme to achieve cooling tower design, and performance analysis, which can make the tedious calculation process procedures. Through the visual user interface meteorological parameters,the cooling tower location parameters,the parameters of the process fluid and operating parameters can be inputed,as the result we can get the final two parts of coil’s size,and the limiting air temperature in which we can turn off the spray water,and we can also get the total investment costs(including initial investment and operating cost).Finally, through the cooling tower design software, the cost per year is made as objective function,the parameters(the tube’s material,length of the tube,and the diameter of the tube) and operating parameters(spray water density,dry air flow rate) is made as the optimization variables, then the influence of different optimization variables to the objective function have been discussed, each variable value corresponds to an optimization scheme therefore this problem can be regarded as a discrete variable optimization problem, enumeration method can be used to solve it,during which all feasible solutions and the objective function need to be listed to select the best solution to achieve the optimal design of the composite cooling tower, reference for the application of this kind composite closed cooling tower is provided.