Solar MEH Desalination Assisted With forced-draft circulation
2019 – 2020
أ.د. السيد صابر
أ.د. أشرف سعيد
Multi-effect humidification (MEH) consists of an evaporator where air is humidified and a condenser where distilled water is recovered. The process occurs under atmospheric conditions by an air loop saturated with water vapor. MEH units are very compact and fall into two types of processes: openwater/closed- air cycle, and open-air/closed-water cycle. There are two types of MEH. In the first type of MEH unit, air circulates between a humidifier and a condenser using natural or forced-draft circulation. Saline water feed is preheated in the condenser by the latent-heat condensation of water that would have been lost in a single-basin still. The feed water leaving the condenser section is further heated in the solar collector before being sprayed over packing in the humidifier section. In the second type of MEH unit, the water heats and humidifies the cold mixed air entering the evaporator. The warm, moist air then enters the condensing section and heats the saline water feed before it is discharged from the system. The MEH principle offers several advantages, such as flexibility in capacity, moderate installation and operating costs, simplicity, and the possibility of using low temperature energy such as solar energy. Two types of energy –low-temperature heat at about 85 °C and electricity– are required in an MEH process. The energy is needed for compensation of sensible heat loss of salt water, pumping salt water, and blowing the air. The largest application of this type of distiller is implemented in Dubai, UAE, and has been operating since 2008. The system consists of a156-m 2 absorber area and 4.8 kW of PV panels. The economic and environmental benefits of the humidification and dehumidification (HDH) desalination technology are enormous including feasibility of being powered by sustainable energy sources such as solar and geothermal, ability to operate at low temperature, low maintenance requirements, and simple construction needs. In the present work, MEH system is modified to increase its efficiency.