International Journal of Modern Engineering Research (IJMER) www.ijmer.com Vol.3, Issue.2, March-April. 2013 pp-962-969 ISSN: 2249-6645 www.ijmer.com 962 | Page Y.B.Karhe, 1 Dr. P.V.Walke 2 1 Student IV Semester, M. Tech. Heat Power Engineering, G.H.Raisoni College of Engineering, Nagpur, India 2 Professor, Mechanical Engineering Departments, G.H.Raisoni College of Engineering, Nagpur, India Abstract: Desalination involves any process in which dissolved minerals are removed from saline or brackish water. The paper evaluates the characteristics for several layouts for the humidification dehumidification desalination process. It gives bird-eye view to Humidification-Dehumidification (HDH) process by comparing various authors’ works. Necessary schematic figures, graphs between affecting operational and environmental parameters and tables are reviewed. Particular attention was given to all vital components in the system. It is concluded that HDH technology has great promise for decentralized small-scale water production applications, although additional research and development is needed for improving system efficiency and reducing capital cost. Keywords: Humidification-Dehumidification (HDH), Desalination, Double Glazing, Heat Exchanger, Closed Water Open Air System (CWOA), Conventional desalination system, solar air heater. I. Introduction There are two main challenges for the world in the future, shortage of energy and shortage of fresh water, both play a crucial role in the overall economic development of any country [19].Conventional desalination technologies are usually large-scale, technology intensive systems is most suitable for the energy rich and economically advanced regions of the world. They also cause environmental hazards because they are fossil-fuel driven and also because of the problem of brine disposal. In the following sections these conventional desalination technologies are introduced and their drawbacks are discussed .These heaters can amount to over 40% of the total cost of a humidification-dehumidification system and so the development of a cost effective and efficient solar collector is essential to the system‘s overall feasibility [1]. II. Conventional Desalination Technologies Desalination processes. Phase-change processes 1. Multi-stage flash (MSF) 2. Multiple effect distillation (MED) 3. Vapor compression (VC) Membrane processes 1. Reverse osmosis (RO) 2. Electrodialysis (ED) Multi Stage Flash (MSF): Pressurized seawater [2, 8] flows through closed pipes where it exchanges heat, with vapour condensing in the upper sections of the flash chambers. Water is then heated to a certain initial high temperature, using burnt fuel or external steam, and this allows flashing along the lower part of the chambers, from chamber to chamber under reduced pressure conditions. Vapour generated is allowed to flow through a mist eliminator to meet the condensing tubes, where heat is transferred to the heating feed seawater. The condensate drips into collectors and is pumped out as the plant product. Exhausted brine, concentrated in salt, is pumped out and rejected to the sea. Part of the brine is recirculating with the feed in order to increase water recovery. Multi-effect Distillation (MED): Basically, the method [2, 17] can use low temperature, low-pressure steam as the main energy source. Steam from burnt coal or fuel can be used, as well as spent steam emerging at the outlet of a steam-operated power station. The primary steam is used to evaporate heated seawater and to generate more steam at a lower pressure, while the primary steam condensate is taken back to the generation chamber, or to the steam generator of the power station. The secondary steam generated goes into a second stage to condense while transferring the latent heat to low temperature seawater, flowing in falling film. The process is repeated as many times as the design permits, between the upper possible temperature and the lower possible cooling temperature, which depends on seawater temperature. The condensate is accumulated stage wise as the product water. A vacuum pump takes the remaining vapour after the last condensation stage, to maintain the gradual pressure gradient inside the vessel. A Solar Desalination System Using Humidification- Dehumidification Process- A Review of Recent Research