Investigation Of Thermodynamic Properties For Working Pairs Of Absorption Refrigeration System On The Basis Of Phase Equilibrium Theory

Absorption refrigeration is one of the refrigeration methods which can make use of low quality heat sources. Some HFC refrigerants have been put forward in the absorption refrigeration systems for their good properties. To make the HFC refrigerants better applied in the absorption refrigeration system, selecting suitable absorbent for the specified refrigerant is one of the key tasks. While, it is impossible to study all kinds of working pairs in absorption system by experimental method. Vapor liquid equilibrium(VLE) data is the basis of calculating thermodynamic properties and system performance. Thus, through studying the VLE data, and analyzing the relationship between thermodynamic properties of working pairs and system performance, finally we can conclude the assessment method to evaluate the potential of working pairs.In this work, a comprehensive assessment method was concluded through theoretical analysis, and the VLE data of R1234yf+NMP, R1234yf+DMETrEG, R152a+DMETrEG are measured. These works provided the basic data for investigating performance of HFCs+absorbent in absorption system, and indicated the direction of the system experiment. The main aims in this work are as follows.(1) Based on the investigation of literature, assessment criteria including p (bubble point pressure), GE (Excess Gibbs free energy) and dR (deflation ratio) were selected to combine and form the assessment method. It can be found that:First, the working pairs with too large differential pressure can excluded by estimating differential pressure based on p; Second, small value of the GEmax means the strong absorption ability of absorbent, and there exist a best range of GEmax. When the GEmax of the working pairs fall in this range, the system can get better performance; Finally, the bigger dR meant the better cycle performance. This assessment method considerd the influence of thermodynamic properties of working pairs on COP as well as f (circulation ratio) and Wp (power consumption of solution pump).(2) The experimental apparatus was reformed for the VLE measurement of HFCs+absorbent:By-pass line was added to improve liquid circulation; 4 port internal (fixed volume) was used as the sample valve, and analysis condition of gas chromatogragh was adjusted to improve peak shape and reduce experiment error.(3) The VLE data of R1234yf+NMP, R1234yf+DMETrEG, R152a+DMETrEG from (293.15～353.15)K are measured by dual cycle method. The VLE data were correlated by NRTL model, and results shew they had a good agreement. Comparative analysis was carried out for several R1234yf+absorbent and R152a+absorbent working pairs to verify the feasibility of assessment method.