Performance analysis of a new type desalination unit of heat pump with humidification and dehumidification

Desalination with humidification and dehumidification process is deemed as an efficient and promising means of utilizing the condenser and evaporator of heat pump to produce freshwater from seawater. This paper presents a new type desalination unit driven by mechanical vapor compression pump which was designed and fabricated by the Institute of Air-Conditioning & Solar Energy of the Northwestern Polytechnical University. The unit utilized the heat from condenser and the cold from evaporator of heat pump adequately, and reclaimed most latent heat. The air, firstly, was humidified in the humidifier with the alveolate structure, and then was cooled in the precondenser and the evaporative condenser to produce freshwater. A mathematical model of the unit is presented, in which the hydrokinetics method was used to study the flow and the heat and mass transfer inside the alveolate humidifier. The effects of some of the operation such as flow rates, temperatures of cooling water and air, and etc., were studied in detail. The comparison between the numerical and experimental results was accepted. The desalination unit that is considered in the study produces freshwater 60 kg/day with the less electric power that is 500 W and is proven to be an efficient desalination device to obtain freshwater.

Fig. 5. Effect of cooling inlet seawater temperature on freshwater production. A new desalination system of heat pump was proposed and a mathematical model was presented. Simulation results were in agreement with the experimental data. The results of this study indicate that the mass flow rate of cooling seawater and the cooling inlet seawater temperature have the apparent effect on the freshwater yield of the desalination system. Approximately, when the mass flow rate of cooling seawater is larger and the cooling inlet seawater temperature is lower, the water yield of system is more. It is worthy of being attention that the matching the mass flow rate of cooling seawater and the cooling inlet seawater temperature for the system desalination. From the application standpoint, the system produces freshwater 60 kg/day with the less electric power that is 500 W (compressor rated power) and the desalination has the advantages that the fee of maintenance is little and operating is easy. If much freshwater is needed, the more power system can be constructed to satisfy the requirement by the appropriate proportion. So, the system is more fit for the people of the remote area to use.