Hermetic Swing Expander in Transcritical Carbon Dioxide
Cycle Water Source Heat Pump

LI Minxia  MA Yitai  AN Qingsong  SU Weicheng

(Thermal Energy Research Institute, Tianjin University, Tianjin 300072)

Abstract: Due to the advantage of global environmental protection, carbon dioxide, the natural refrigerant, has been attracting increasing attention over the last ten years. The low performance efficiency of the CO2 transcritical cycle is the main problem for the practical application. In order to reduce the irreversible loss caused by the throttling process from the supercritical region to the sub-critical and improve the coefficient of performance of CO2 cycle, an expander is adopted to replace the throttle valve and recover the expansion power. A hermetic swing expander in transcritical carbon dioxide cycle water source heat pump is developed. The structure of swing expander and stress on the swing piston are analyzed. The experiment on CO2 transcritical cycle water source heat pump is conducted. The results indicate that swing expander is suitable for the operation under high pressure. Under the test condition, the efficiency of the swing expander can reach 44%.

Key words: Carbon dioxide transcritical cycle  Swing expander  Water source-heat pump

CLC No: TU83

国家自然科学基金资助项目(50506019). Received 20070617, received in revised form 20080124

References

[1] LORENTZEN G. The use of natural refrigerants: a complete solution to the CFC/HCFC predicament[J]. International Journal of Refrigeration, 1995, 18(3): 190-197.
[2] LORENTZEN G, PETTERSEN J. A new efficient and environmentally benign system for car air-conditioning[J]. International Journal of Refrigeration, 1993, 16(1): 4-21.
[3] KIM Man-Hoe, PETTERSEN Jostein, BULLARD C W. Fundamental process and system design issues in CO₂ vapor compression system[J]. Progress in Energy and Combustion Science, 2004, 30: 119-174.
[4] MA Yitai, YANG Zhao, LÜ Canren. Thermodynamic analysis of CO₂ transcritical cycle[J]. Journal of Engineering Thermophysics, 1998, 19(6): 665-668.
[5] MA Yitai, WANG Kanhong, YANG Zhao, et al. Thermo-dynamic analysis on CO₂ transcritical cycle with expander[J]. Journal of Engineering Thermophysics, 1999, 20(6): 661-665.
[6] ROBINSON D M, GROLL E A. Efficiencies of transcritical CO₂ cycles with and without an expansion turbine[J]. International Journal of Refrigeration, 1998, 21(7): 577-589.
[7] PREISSNER M. Carbon dioxide vapor compression cycle improvements with focus on scroll expanders[D]. Univer-sity of Maryland College Park, 2002.
[8] BAEK J S, GROLL E A, LAWLESS P B. Piston-cylinder work producing expansion device carbon dioxide cycle. Part I: experimental investigation[J]. International Journal of Refrigeration, 2005, 28: 141-151.
[9] BJORN F. Feasibility study of using centrifugal compressor and expander in a car conditioner working with car-bon dioxide as refrigerant, ACRC CR-23 [OL]. http: // acrc.me.uiuc.edu/publications.asp.
[10] TONDELL E. Impulse expander for CO₂[C] // 7th IIR Gustav Lorentzen Conference on Natural Working fluids, Trondheim, Norway, Trondheim, SINTEF Energy Re-search Institute, 2006: 107-110.
[11] ZHA Shitong. Study and development of CO₂ transcritical expander[D]. Tianjin: Tianjin University, 2002.
[12] MASAYA T, TOSHIYUKI E, ALSUSHI O, et al. Devel-opment of the CO₂ hermetic compressor[C] // The Pro-ceedings of the 4th IIR-Gustav Lorentzen Conference on Natural Working Fluids, Purdue, USA, Purdue University, Purdue University, 2000: 323-330.