Research On Optimization Of Numerical Simulation Of Activated Carbon-Ethanol Adsorption Refrigeration System

With the rapid development of the global economy,the world’s primary energy consumption has increased year by year.At the same time,in the process of energy development and utilization,environmental pollution problems have become increasingly serious.Traditional vapor compression refrigeration technology uses refrigerants such as chlorofluorocarbons(CFC),hydrochlorofluorocarbons(HCFC)and hydrofluorocarbons(HFC),which cause the greenhouse effect and also deplete the ozone layer.Adsorption refrigeration is a green and environmentally friendly technology that uses thermal energy as the driving energy source.It has been widely researched and applied in recent years,but its disadvantages such as low system efficiency and large system size have restricted its application and development.In view of the low efficiency of the adsorption refrigeration system,this paper uses a high-performance adsorption working pair(activated carbon Maxsorb Ⅲ-ethanol),selects a finned tube heat exchanger,focuses on the core component of the adsorption refrigeration system——the adsorption bed,and uses the distributed parameter method to establish the calculation model.The calculation program is built with CFD software,and the dynamic simulation of the heat transfer and mass transfer process of the adsorption bed and the operation process of the circulating refrigeration system with or without mass recovery is carried out.During this process,the effects of the performance parameters of the adsorbent and the system operating conditions on the refrigeration system are clearly defined.The main research content and conclusions of this article includes the following three aspects:(1)Based on the analysis of the Maxsorb Ⅲ-ethanol adsorption process,a finned tube adsorption bed model was established,obtain the distribution of physical quantities such as adsorption amount,temperature,and pressure during desorption in the adsorption bed with the help of numerical simulation method,and clarify the effect of total porosity and adsorbent particle size on the heat and mass transfer performance in the adsorption bed,obtaining the following conclusions:when the total porosity(εt)is around 0.65,the average adsorption capacity and total desorption amount of the adsorption bed reaches a better value,and the adsorption bed has good heat and mass transfer performance;under the condition of a fixed cycle period,a higher porosity is beneficial to the improvement of SCP;In order to improve the system COP,the adsorbent with too low porosity should not be selected;when the manufacturing process and cost of the adsorbent are not considered,the adsorbents with smaller particle size are supposed to be chosen.(2)Build a model of Maxsorb Ⅲ-ethanol double bed adsorption refrigeration system,use CFD simulation software to perform dynamic simulation analysis on its operation process,and study the influence of working temperature parameters such as operating temperature,cycle period,preheating/cooling time on the refrigeration system.The research results show that:the heat source temperature is the main factor affecting the refrigeration system SCP.When the heat source temperature rises from 343.15K to 373.15K,the system SCP increases by 131%.The cycle period has the greatest impact on the COP of the refrigeration system.In the range of 400s-1600s,the system COP is increased by a maximum of 53%.In addition,the COP and SCP of the refrigeration system will increase first and then decrease with the extension of the preheating/cooling time;a higher evaporation temperature and a lower condensation temperature will significantly improve the performance of the refrigeration system.(3)Build an Maxsorb Ⅲ-ethanol adsorption refrigeration system with a mass recovery cycle,and carry out the simulation to explore the impact of the mass recovery cycle on the adsorption refrigeration system,while obtaining the influence law of the cooling/heat source temperature,pre-cooling/heating time and cycle time on the system COP and SCP.According to the simulation results,under the same conditions,the system with increased return-to-mass circulation shows a clear advantage over the basic system.When the temperature of the cold and heat sources were 298.15K and 363.15K,respectively,by performing mass recovery for 50 seconds,SCP increased by 8%and COP increased by 17%compared to the basic cycle.SCPs of systems with different quality recovery times all achieve the maximum value at the pre-cooling/heating time of 20s.When the mass recovery time is 50s,the maximum value is obtained.Compared with the basic circulation SCP,the improved system SCP increases by 9%,and the COP increases by 16%.In summary,this paper has carried out research and system optimization on the heat and mass transfer process of the Maxsorb Ⅲ-ethanol adsorption bed and the refrigeration system with or without mass return cycle,which provides theoretical guidance for the design and development of the activated carbon adsorption refrigeration system.