Analysis and optimization of subcritical two-stage vapor injection heat pump systems

Two of the major problems of heat pump systems working in extreme conditions are the loss of efficiency of the system and the high compressor discharge temperatures. One possibility in order to overcome these issues is to perform the compression in two stages. In this frame the use of vapor injection two stage cycles represent an economic and effective solution. This study analyzes the influence of design parameters and injection conditions for two different configurations of two stage cycles, for four refrigerants (R407C, R290, R22 and R32). Design parameters, such as the displacement ratio, are optimized in terms of COP in ideal conditions for both injection systems. A deeper analysis taking into account the efficiencies of the compressor is done finding that two stage systems could reach improvements of 30% in terms of COP compared with one stage systems and that a bad design of this type of systems could represent a loss of improvement between 6% and 10%. Finally a method to control the system at any operating point in order to make it works in its optimum is done. From all the analysis, guidelines for the optimum design and control of such systems are obtained in terms of capacity, Coefficient of Performance (COP), seasonal performance factor and discharge temperature criteria.

[1]  Jean Lebrun,et al.  Scroll compressors using gas and liquid injection: experimental analysis and modelling , 2002 .

[2]  Xianting Li,et al.  Numerical analysis on the effects of refrigerant injection on the scroll compressor , 2006 .

[3]  Baolong Wang,et al.  Design of experimental bench and internal pressure measurement of scroll compressor with refrigerant injection , 2007 .

[4]  Ma Guoyuan,et al.  Experimental investigation of air-source heat pump for cold regions , 2003 .

[5]  Wenhua Li,et al.  Simplified modeling analysis of mass flow characteristics in electronic expansion valve , 2013 .

[6]  Rachid Outbib,et al.  Energy production for dwellings by using hybrid systems based on heat pump variable input power , 2015 .

[7]  E. Groll,et al.  Two-stage air-source heat pump for residential heating and cooling applications in northern U.S. climates , 2008 .

[8]  Piotr A. Domanski,et al.  Theoretical Evaluation of the Vapor Compression Cycle With a Liquid-Line/Suction-Line Heat Exchanger, Economizer, and Ejector (NISTIR 5606) , 1995 .

[9]  W. B. Gosney.  Principles of Refrigeration , 1982 .

[10]  Roberto Cipollone,et al.  Theoretical modeling and experimental investigations for the improvement of the mechanical efficiency in sliding vane rotary compressors , 2015 .

[11]  J. W. Ramsey,et al.  Thermal Environmental Engineering , 1970 .

[12]  Guo-yuan Ma,et al.  Characteristics of an improved heat-pump cycle for cold regions , 2004 .

[13]  Honghyun Cho,et al.  Mass flow characteristics and empirical modeling of R22 and R410A flowing through electronic expansion valves , 2007 .

[14]  K. Umezu,et al.  Heat pump room air-conditioner using variable capacity compressor , 1984 .

[15]  I. B. Vaisman.  Economizer Cycle In Air Conditioning Systems with Rotary Vane Compressors , 2000 .

[16]  Jain Siddharth,et al.  Vapor Injection in Scroll Compressors , 2004 .

[17]  Reinhard Radermacher,et al.  Performance Investigation of Refrigerant Vapor-Injection Technique for Residential Heat Pump Systems , 2008 .

[18]  Syed M. Zubair,et al.  Second-law-based thermodynamic analysis of two-stage and mechanical-subcooling refrigeration cycles , 1996 .