New Organic Working Pairs Design For Absorption Heat Pump Cycle

Under the policy guidance of "carbon peak" and "carbon neutral",the efficient use of energy is one of the most important research directions today.Since the absorption heat transformer can directly use the waste heat at the middle temperature in industrial production to produce higher temperature heat,it is widely used in the research of waste heat recovery systems.The working pairs is the key factor that determines the operating conditions and thermal efficiency of the absorption heat transformer.However,the most widely used Li Br/H2O working pair cannot meet the working requirements of some conditions due to defects such as crystallization and limited working temperature range.Therefore,looking for new working fluid pairs has broad research prospects.Nowadays,most of the researches focus on the experimental regression of the physical parameters of the specific working fluid.They are time-consuming and costly.The research in molecular design mostly focuses on the design of a single refrigerant or absorbent,ignoring the interaction between the absorbent and the refrigerant and the influence of thermodynamic processes on the working fluid.Therefore,it is a key problem to be solved urgently to establish a design scheme of absorption heat transformer working pairs that considers the thermodynamic process.This paper establishes a computer-aided molecular design method for absorption heat transformer working pairs,and adapt it to processes such as single-effect absorption heat transformer and compression-absorption coupled heat pumps to explore the new working pairs in a variety of heat pump cycles.First of all,in the physical property method,the group regression parameters of the constant pressure specific heat of organic refrigerants have been improved.The average prediction error of the new group contribution method is less than 10%,which is 1/2 of the prediction error of the general group contribution method.By combining the CAMD and COSMO-SAC models to predict the activity coefficient between the working pairs and the mixing enthalpy of the solution,the error of the coefficient of performance calculated using the TFE/E181 working pairs under the same conditions is less than 5%.In the design of working pairs,the reliability of the design results was verified by the existing working pair TFE/E181 in the design results,CH3CH2CH(OH)CH2CF3/TEGDME and CF3CH2CH(OH)CH2CF3/TEGDME were applied under the operating conditions of higher than 130℃,the coefficient of performance is above 0.4,which is greater than the existing TFE and HFIP refrigerants(0.35),which reflects the potential of the new working fluid in the high temperature area.In the expansion of the heat pump model,the superstructure model of the absorption heat pump was established and applied to the compression-absorption cycle with two new working fluid pairs.From the design results,it can be obtained that the designed new working fluid pair CF3CH2CH(OH)CH2CF3/TEGDME can be applied to the absorption-compression coupling cycle,and the exergy loss under the best working condition is about 10% lower than the Li Br/H2O cycle exergy loss under the same condition.