Absorption refrigeration has become the focus of research in there refrigeration field in recent years because it has a lot of merits such as little power consumption，great energy adaptability， no influence for the environment about working fluids etc. As a clean energy，natural gas will be applied extensively in the energy consumption structure. So research of gas-fired air conditioning has an important theoretical and practical significance .In this paper，a new type of absorption refrigeration system-middle pressure double-effect cascade cycle was studied. The aim is to meet gas-fired air conditioning miniaturization and air-cooling. In addition，the system should have high Coefficient of Performance(COP).
A general program was compiled to calculate the thermophysics property of ammonia-water solution on the base of research of others. The result is tallied with the data which literature has given. So the program can be used to design ammonia-water absorption refrigeration system.
The middle pressure double-effect cascade cycle was studied and analyzed. The analyzed result indicates that rectified heat should be reclaimed in such systems. A mathematic model about this system was established. Performance of this system and its influencing factor was calculated and analyzed exclusively. Those conclusions provide theoretical method for designation of such kind of absorption refrigeration system.
In addition，exergy loss about the system was studied. The result indicates that generator and absorber and solution heat-exehange equipment have a high exergy loss. Those conclusions provide a basic guideline for further effective use energy and proceed system optimization.
KEYWORDS: ammonia-water solution，absorption refrigeration system，exergy loss，rectified heat，air-cooling，gas-fired.
