A Theoretical and Experimental Study for A humidification-Dehumidification (HDD) Solar Desalination Unit
A humidification-dehumidification (HD) solar desalination unit was designed. It seems to be suitable to provide drinking water for population or remote arid areas. Solar water and solar air collectors were designed to provide the hot water and air to the desalination chamber. The desalination chamber was divided into humidifier and dehumidifier towers. The circulation of air in the two towers was maintained by the forced convection. Theoretical and experimental works were done at different environmental conditions. A mathematical model was formulated, in which the thermodynamic relations were used to study the flow, heat and mass transfer inside the humidifier and dehumidifier. Such a technique was performed in order to increase the unit performance. Heat and mass balance was done and a set of governing equations was solved using the finite difference technique. The solar intensity was measured along the working day during the summer and winter months and a comparison between the theoretical and experimental results were performed. The average accumulative productivity of the system in November, December and January was ranged between 2 to 3.5 kg / m day while the average summer productivity was found between 6 to 8 kg/m day in June and 7.26 to 11 22
Energy Consumption Minimization of a New Desalination System
Demand for fresh water has increased very dramatically in recent years due to the huge increase of the population and the great development in industry and agriculture. Among many water treatment technologies, seawater desalination process is the ideal solution to address the problem of the shortage of fresh water in many places around the world. However, energy consumed in the desalination process is the major challenge which faces its success in solving the problem of the shortage of fresh water. Generally, desalination process consumes a very large amount of energy. The majority of this energy comes from fossil fuel sources, which is the main source of environmental pollution and global warming. Reducing the energy consumed in the desalination process is a key factor for cutting the cost of fresh water produced by the desalination process. For this purpose, a new system has been developed for water desalination through integration of the heat pump system and humidification and dehumidification technology. The energy consumption in the desalination process was minimized by controlling the water and air flow rates in the new system. The results showed that 1.71 kg/hr of fresh water can be produced using only 0.726 kWhr. This result is an important achievement in reducing the energy consumed in the desalination process. Keywords—component; Humidification-Dehumidification, Desalination, Minimum Energy , Heat pump,
Heat pumps as a source of heat energy for desalination of seawater
Thermal desalination plants consume large quantities of heat energy for seawater evaporation. In condensing water vapor procured in evaporators and cooling distillate, a major part of heat energy is lost in the environment. Heat energy in processes of condensation and evaporation in desalination of seawater is quantitatively equal but these processes take place under different temperatures. Different power plants such as turbines of thermal and atomic power stations usually are the source of heat energy for the desalination process. Extraction of heat for evaporators for desalters reduces heat and electric power production of power plants. Besides emission of heat, energy from desalters in the environment results in its heat pollution, a greenhouse effect. Thermodynamic analysis described in this paper shows that the heat pumps make it possible to use heat energy effectively at desalination plants. It is provided with the incorporation of a heat pump in the flow diagram of the desalination plant.