Performance Analysis And Evaluation For An Absorption Refrigeration Coupled With A Liquid Dehumidification System Driven By Low-grade Waste Heat

At present,the main energy consumption fields in China are the industrial field and the construction field.The industrial process generated huge amount of low-grade waste heat which is hard to be effectively recovered and utilized.In the construction field,the HVAC is the main energy consumption equipment.The traditional HVAC has lower efficiency and is hard to utilize energy effectively.The HVAC driven by the low-grade waste heat can not only realize the efficient utilization of the energy,nut also improve the efficiency of HVAC.Thus,this thesis proposed a cascade system combined an absorption refrigeration system and a liquid dehumidification system.Compared with the traditional energy system,the proposed system has better efficiency and can effectively utilize the low-grade waste heat.First of all,according to the energy cascade utilization method,the cascade system combined an absorption refrigeration system and a liquid dehumidification system driven by low-grade waste heat was proposed.And the models of the proposed system were conducted.The proposed system is consisted of an absortion refrigeration system and a liquid dehumidification system.The combination between the evaporator of the absorption refrigeration system and the condenser of the liquid dehumidification system realized the energy cascade utilization.Based the Aspen Plus software,the models for the proposed system were conducted.According to the data of literatures,the validation of the proposed system was conducted.The performance of the proposed system was being obtained from the viewpoint of thermodynamic index,the dehumidification index,the exergy index,the economic index.And the analysis for the key parameters of the subsystems was conducted.Secondly,the thermodynamic performance,the dehumidification performance,the exergy performance and the economic performance of the proposed system were analyzed from the simulation results.The thermodynamic performance and the dehumidification performance indicated that the increase of the refrigeration temperature is harmful to the system efficiency.With the refrigeration temperature of 2℃,the optimal COP,enthalpy efficiency,moisture removal rate and humidity efficiency are 0.61、0.80、20.20g/kg and 0.94 respectively.The exergy performance showed that the exergy efficiency of the proposed system reduces from 10.34%to 10.06%with the refrigeration temperature increasing to 10℃.The economic performance indicated that the increase of the refrigeration temperature is advantageous to the economic performance of the proposed system.With the refrigeration temperature of 10℃,the lowest total annual cost of the proposed system is 5.77×10~5$.Then,this thesis conducted the multi-objective optimization of the proposed system with total exergy destruction,COP and total annual cost as objective functions.Under the optimal solutions,the low-grade waste of 90-109.99℃is used for absorption refrigeration system and the low-grade waste heat of 109.99-150℃is used for liquid dehumidification system.The total annual cost,COP,and the total exergy destruction of the proposed system are 5.86×10~5$,0.60 and 337.17k W respectively.The deviation between the optimal performance indicators with the best value of the performance indicators are 1.54%,1.64%and 0.08%respectively.The research results showed that the optimal solutions can effectively trade off the performance of the coupled system.Finally,the life cycle assessment of the proposed system was conducted by the Ga Bi software.Based on the Recipe2016 method and Eco-indicator 99 method,the indicators for life cycle assessment had been normalized and weighted to get the single evaluation index:EI16.The life cycle assessment results indicated that the contribution of the construction phase for the environment damage is the largest.And the second largest is demolition phase.The improvement to the environment at the usage phase determines the environment efficiency of the proposed system.Meanwhile,the improvement for the manufacturing and recovery technique of stainless steel,copper and rubber can enhance the environment efficiency of the proposed system.