Study On Cooling Performance And Software Development Of An Air-cooled And Evaporating Hybrid Cross-flow Closed Cooling Tower

The cross-flow cooling tower is a kind of common cooling device in the air conditioning system and industrial production.It uses air and spray water as medium to cool the working fluid for meeting cooling requirements.As a new type of high-efficiency cross-flow cooling tower,the air-cooled and evaporating hybrid cross-flow closed cooling tower is a series of finned tubes and light pipes,and the spraying device is arranged above the light pipe area.By air cooling and evaporating double cooling modes to achieve the purpose of cooling the working fluid.In order to ensure the quality of the cooling water in the tube and reduce the evaporation loss,a type of air cooling and evaporation double cooling tower was used widely.Based on the combination of numerical simulation and software development,this paper studies the influence of the internal structure and operating parameters on the cooling performance of cross-flow tower.The applicability of different operating modes of the hybrid cross-flow tower under different seasonality was obtained and its optimization control strategy was developed.Based on this,thermal calculation software suitable for engineering applications was improved.In the field of numerical simulation,the heat and mass transfer equations of the fin tube region,the light tube region and the packing region of the hybrid cross-flow tower are established by MATLAB software,and the influence of the structural and operating parameters on the cooling water outlet temperature and cooling efficiency is numerically simulated.The results show that the cooling efficiency of the cooling water is increased with the increase of the number of single pipe pipe,the number of tubes and the length of the single pipe of the coil pipe.On the contrary,with the increase of the tube spacing,the cooling water outlet temperature increases and the efficiency decreases.In terms of operating parameters the cooling water outlet temperature and cooling efficiency are raised with the increase of the air wet-bulb temperature.With the increase of the flow rates of air and spray water,the cooling water outlet temperature and cooling efficiency both decrease.And the increase of the cooling water flow rate will make the increase of cooling water outlet temperature and the reduction of the cooling efficiency.Moreover the change of air wet bulb temperature and cooling water flow rate has the most influence on the cooling efficiency among all the influence parameters.In terms of operation mode control strategy,taking the meteorological conditions in Nanjing as an example,MATLAB was used to study the applicability and control strategies of different operation modes under different meteorological conditions.Research shows that due to the different applicability of various operating modes under different meteorological conditions,in order to full use the advantages of the hybrid cross-flow tower,the operating mode conversion conditions must be optimized.Taking the composite transverse flow tower studied in this paper as a model,valves are arranged at the inlet and outlet of the cooling tower heat exchange coil and the spraying device.Four modes of operating which are the air-cooling of the finned tube,the air cooling of the finned tube and the light pipe,the evaporating cooling of the light pipe,and the air cooling of the finned tube and the evaporating and cooling of the light pipe can be realized by controlling the opening and closing of the valve.In order to meet the cooling requirements,when the air dry bulb temperature is less than 30℃,the air-cooling of the finned tube mode can be chosen;when the air dry bulb temperature between 30℃-33℃ the evaporating cooling of the light pipe mode can be chosen;if the air dry bulb temperature between 33℃-34.5℃,then select the hybrid cross-flow closed mode.When the air dry bulb temperature exceeds 34.5 ℃,the all four modes can not meet the cooling requirements,and when the air dry bulb temperature exceeds the cooling water inlet temperature,the finned tubes area does not have any cooling effect,if still need cooling tower to dissipate heat,the last mode can be chosen.In software development,in order to make the research results convenient for in engineering applications,the thermal calculation software of the composite cross-flow closed cooling tower was developed by using MATLAB.The software consists of three programs,the corresponding combination of programs can be ensured by choosing different modes and the thermodynamic calculation results can be obtained by inputting parameter.The applicability of the cooling tower in different operating modes can be easily judged under different climatic conditions by using the software.The aim of this paper is to find out the effect of structure and operation parameters on the cooling performance of the hybrid cross-flow closed tower,obtain the optimal control strategy of seasonal operation mode,and develop a thermodynamic calculation software for cross-flow tower which is convenient for engineering application.Theoretical basis and technical support are provided for further research and development of the cross-flow tower...