Computer simulation on dynamic behaviour of a hot water driven absorption chiller

Abstract

The dynamic behaviour of a 40 RT (140 kW) absorption chiller driven by hot water has been numerically investigated. The thermal models for the components of the system have been developed to investigate the dynamic behaviour of the system at off-design conditions, such as the change in heat transfer medium temperature or the construction change of the system components. A sudden change in hot water temperature results in the very rapid change at the beginning. The change becomes slower and slower and ultimately the system reaches a new steady state. The COP at the new steady state is hardly affected by the variation of hot water inlet temperature, while the variation of cooling capacity is almost proportional to the hot water temperature. Similarly, the effect of a sudden change in cooling water temperature has been investigated. It is found that the (UA)-value below the design point causes significant damage to the system COP and the cooling capacity, while the increase above the design point gives only a little improvement. A proper solution circulation rate should be chosen to improve the COP without crystallization. The simulation describes the cooling capacity control process well and a desired cooling capacity can be obtained by controlling the mass flow rate of hot water.