Dynamic modelling and simulation of a gravity-assisted solution pump of a novel ammonia-water absorption refrigeration unit

This work presents a comprehensive modelling and simulation of a heat-driven gravity-assisted solution pump for an aqua ammonia absorption refrigeration unit. The pump is essentially a hermetic vessel located at an intermediate elevation between the absorber and generator. It is connected to both components with vapour and liquid tubes. The flow in the vapour tubes is controlled by solenoid valves, while a regulating valve and two non-return valves are incorporated in the liquid tubes. The developed pump overcomes the leakage problem which is still a major constraint in developing ammonia-water refrigeration and heat pumping systems of small capacities. The simulation results revealed that the diameter of the pump vessel has no effect on its flow rate. The elevation differences have a slight effect on the flow rate. The most important parameters are the diameter of the liquid tubes and the pressure loss coefficients of the incorporated regulating and non-return valves. The obtained results pave the way to implement this type of solution pumps in the development of small capacities ammonia-water absorption refrigeration units. (c) 2005 Elsevier Ltd. All rights reserved.