Refrigeration absorption cycles with ammonia-water driven by low temperature heat sources

At present much interest is being shown in cycles working with low temperature heat sources. They can use low temperature waste heat or extract more heat from waste streams and use it to produce cold. In our case we are interested in producing of subzero temperatures (-5 degrees C). Cycles are simulated with generator temperatures between 60 and 110 degrees C and absorber temperatures between 35 and 50 degrees C and compared to a single effect cycle. The most suitable working pair for this application is the natural working fluid, ammonia with water as absorbent, associated to advanced absorption cycles which are adapted to these specific conditions. The cycles studied are the double lift series flow, the double lift vapour exchange and a triple lift cycle. The working range of the double lift cycle is significantly wider than the single effect, and that of the triple lift is even larger. The COP for the double lift cycles is about 0.35, while that of the triple lift is much lower. Therefore the double lift cycles and especially the vapour exchange cycle, seem more interesting than the triple effect, also because of their less complex structure. Further work will be done on other double lift cycles such as the Semi-GAX cycle and on other environmental friendly working pairs.