A new open absorption heat pump for latent heat recovery from moist gas

Conventional drying processes discharge high humidity gas to the atmosphere. The exhaust gas contains large amount of energy. The direct discharging would result in relatively large energy waste. In order to improve the thermal efficiency of drying process, in this paper, a new open absorption heat pump system was proposed, which aims at recovering the latent heat from exhausted moist gas and producing steam for reutilization. The working principle was discussed in detail and thermodynamic models were established to analyze the performance of the new system. The new system can work under both single-stage and double-stage modes. Simulation results showed that the new system could utilize a heat source with lower generation temperature compared with that utilized by a traditional open absorption system. The temperature range of heat source for the double-stage mode is 130-160 degrees C, and that for the single-stage mode is 160-175 degrees C. The new system also eliminates the limitation of traditional close absorption system, whose evaporation temperature has to be lower than the dew point temperature of discharged mbist gas to recover the latent heat of water steam. Simulation results also indicated an improved COPh of the new system compared with that of double-stage close absorption heat pump system. The COPh of the new system varied from 1.52 to 1.97 and the efficiency of heat recovery varied from 15.1% to 54.8% when the temperature of heat source varied from 135 degrees C to 175 degrees C and saturated steam of 100 degrees C was produced. (C) 2015 Elsevier Ltd. All rights reserved.