Investigation of an Energy Source Temperature for NH3 + NaSCN and NH3 + LiNO3 Absorption Refrigeration Systems

Abstract

This paper evaluates the energy source temperature for novel salts based ammonia/sodium thiocyanate (NH3 + NaSCN) and ammonia/lithium nitrate (NH3 + LiNO3) absorption refrigeration systems. Minimum energy source temperature (cutoff) required to initiate the cooling, critical energy source temperature for optimized thermodynamic performance and possible maximum energy source temperature to avoid crystallization have been determined, and empirical correlations are developed to facilitate continuous operation of the system. A comparison of cutoff energy source temperature depicts that the NH3 + NaSCN pair requires averagely 6 –7 °C higher cutoff temperature compared with the NH3 + LiNO3 pair. Contradictory to this, the maximum coefficient of performance (COP) of the NH3 + NaSCN pair is 7.02% higher than that the NH3 + LiNO3 pair. However, NH3 + NaSCN pair operates in a very narrow range of energy source temperature. From the P − T − X diagram, the crystallization phenomenon is clarified and the maximum energy source temperature has been determined beyond which the system would not function due to crystallization problems. For −10 °C evaporator temperature, the energy source temperature should be controlled between 87 °C and 115 °C for the NH3 + NaSCN pair and between 80 °C and 147 °C for the NH3 + LiNO3 pair.