Performance Investigation Of The Heat Pump Assisted Humidification-Dehumidification Desalination System Based On Counterflow Packing Tower

Humidification-dehumidification desalination technology is a new kind of desalination technology.Most of the existing humidification-dehumidification setups air driven by solar energy and thus are restricted by unfavorable climate conditions.To solve this problem,a novel heat pump assisted humidification-dehumidification desalination system based on counterflow packing tower is proposed and a deep investigation of the proposed system is conducted in this paper,which includes the following contents:(1)The counterflow packing tower is an important component of the heat pump assisted humidification-dehumidification desalination system.The mathematical model of heat and mass transfer of the counterflow packing tower is established.The heat and mass transfer balance differential equations are solved by adopting the control volume balance method.In addition,an experimental study on a polypropylene fill is carried out to develop the empirical correlations of the mass transfer coefficient and the air side resistance loss coefficient,which provided theoretical and experimental basis for the performance analysis and optimization of the fill.(2)The effects of spray water mass flow rate,air mass flow rate and packing height on the humidification performance of the packing tower are theoretically analyzed.Based on the multi-objective particle swarm optimization algorithm,the packing volume,specific humidification energy ratio are used as the objective functions by optimizing the spray water mass flow rate,air mass flow rate,fill cross-sectional area and fill height of the packing tower.The impact analysis of various factors on the humidification performance and their optimization provide a theoretical basis for the heat pump assisted humidification-dehumidification desalination system based on the counterflow packing tower.(3)A novel heat pump assisted humidification-dehumidification desalination system based on counterflow packing tower is proposed.The mathematical model of this desalination system is established considering the influence of external parameter changes on the operating state of the heat pump unit,which is closer to the actual operating conditions of the system.The mathematical model is verified by experimental data and utilized to study the effects of air temperature,air humidity ratio,air flow rate,seawater temperature and seawater flow rate on the fresh water production.The establishment of the mathematical model and impact factor analysis provide a theoretical basis for subsequent optimization studies.(4)The multi-objective design optimization of the heat pump assisted humidification-dehumidification desalination system based on counterflow packing tower is conducted in this work.Firstly,the mathematical model of the desalination system is modified by refining the heat pump circulation submodel,in which the heat balance equations of the refrigerant state equation,evaporator and condenser are included.Moreover,the black-box model of the key parameters of the proposed system including system energy consumption rate and fresh water productivity is established through the support vector machine regression method and the calculation speed is significantly improved under the premise of ensuring the calculation accuracy.Then,combined with the monthly typical meteorological parameters,the multi-objective particle swarm optimization algorithm is used to optimize the design of the heat pump assisted humidification-dehumidification desalination system based on the packing tower with three objective functions and eleven control variables.This optimization study provides a design reference for the practical application of heat pump assisted humidification-dehumidification desalination system based on counterflow packing tower.