Study on ammonia/water hybrid absorption/compression heat pump cycle to produce high temperature process water

The objectives of this paper are to analyze the heat transfer characteristics during the ammonia water absorption process for the hybrid absorption/compression heat pump system application. The hybrid absorption/compression heat pump cycle aims at obtaining the high temperature process water. The parametric analysis on the effects of each key parameter, which are system high-pressure, ammonia weak solution concentration, ammonia weak solution and vapor flow rates is carried out. It is found that the increases in the high pressure and ammonia weak solution flow rate have positive effects on the absorber heat transfer rate, whereas the increase in the weak solution concentration does negative effect. It is also found that the weak solution concentration acts as the most important parameter to obtain the high temperature process water. As the weak solution concentration increases, the absorber heat transfer rate decreases, but the system COP tends to increase. It is concluded that the concentration of the weak solution should be maintained at approximately 0.40-0.45, the flow rate of the weak solution be lower than 0.03 kg/s, and the high-pressure be higher than 1700 kPa to obtain process water of higher than 80 °C.