| Energy saving technology is the priority theme of China’s energy strategy development,and energy saving and emission reduction is the basic national policy of China’s energy development.China’s energy consumption is large and energy supply is tight.One of the keys to improve energy efficiency and reduce energy waste is to develop and optimize energy equipment.The advantages of gas air source heat pump in primary energy utilization rate,economic energy saving,waste heat recovery and utilization make it develop rapidly in recent years.As an important part of the heat pump system,the performance of condenser also greatly affects the overall quality of the heat pump system.Because the evaporative condenser has obvious advantages over other types of condensers in terms of water saving,energy saving and comprehensive performance.Therefore,it is of great significance to deeply study the mass and heat transfer process of evaporative condenser,analyze the influence of various factors on its heat transfer performance,and reasonably design and optimize it for the development of China’s energy strategy.In this paper,the research work of evaporative condenser is mainly carried out from the following aspects:Firstly,the classification and performance characteristics of condensers in gas-fired air source heat pump system are analyzed.The basic structure,working principle,tube type and other aspects of evaporative condenser are studied.The mechanism of heat and mass transfer is emphatically analyzed,and the structural design of drop tube evaporative condenser is completed through calculation.Secondly,the simulation model of evaporative condenser is established,and the temperature field and velocity field of circular tube and drop tube evaporative condenser are simulated by using FLUENT software under the same conditions.The accuracy of simulation results is verified by comparing with relevant literature,and it is further proved that the special arc surface design of drop tube can improve the heat transfer performance of evaporative condenser.Using the control variable method,the liquid distribution height,spray water spray speed,spray water spray temperature,arrangement angle and tube bundle spacing are taken as variables respectively,and other parameters are controlled unchanged.The influence of each single factor on the heat transfer performance of drop tube evaporative condenser is simulated and analyzed,and its structure is optimized.The results show that: when the liquid distribution height is set as a variable,from the aspect of heat exchange performance,the liquid distribution height is 250 mm,from the aspect of thermal economy,the liquid distribution height is 300 mm;when the spray water speed is set as a variable,from the aspect of heat exchange performance,the spray water speed is 1.4 m / s,from the aspect of thermal economy,the spray water speed is 1.6 m / S;the spray water temperature is set The results show that there is an optimal temperature of 30 ℃when the temperature is the variable,and the condenser has the best heat transfer performance;when the tube bundle arrangement is set as the variable,the arrangement is 10 ° parallel,but the energy loss is too much,considering the heat economy,the normal arrangement is the best;when the tube bundle spacing is set as the variable,the tube bundle spacing is 48 mm,the heat transfer performance is the best,and the tube bundle spacing is 48 mm 50 mm is the best thermal economy.Finally,considering that the heat transfer performance of the drop tube evaporative condenser is determined by many factors,the influence degree of these factors can not be distinguished by single analysis,the orthogonal test method is used to calculate the combination of four important factors,and the primary and secondary relationship of the influencing factors is spray water speed > tube bundle spacing > liquid distribution height > spray water temperature;and the most optimal combination is proposed The results show that when the height of liquid distribution is 250 mm,the temperature of spray water is 29 ℃,the speed of spray water is 1.4m/s,and the spacing between tube bundles is 48 mm,the heat transfer coefficient of drop tube evaporative condenser is the highest and the heat transfer performance is the best. |
