International Conference on Mechanical, Industrial and Energy Engineering 2010 23-24 December, 2010, Khulna, BANGLADESH
Construction and Performance Test of Solid Desiccant Cooling System Md. Hasan Ali1, A. N. M. Mizanur Rahman2,,*, N. U. I. Hossain2, K. S. Islam2 1 Department of Energy Technology, 2 Department of Mechanical Engineering Khulna University of Engineering & Technology, Khulna-9203, Bangladesh ABSTRACT Apart from the conventional cooling, there are other methods that are employed for specific applications. Evaporative cooling comes under this category. This type of cooling has a great potential to provide thermal comfort in places where humidity is low. A way to solve this problem of high humidity is to use dehumidifiers for preconditioning the process air. Desiccant evaporative cooling (DEC) system has been proposed as energy saving alternatives to conventional cooling systems. In desiccant cooling, the air is first dehumidified before its temperature is reduced by evaporative cooling. Desiccant materials remove moisture from humid air, when air is passes through the desiccant. Use of solid desiccants offer several designs and performance advantages over liquid desiccants, when solar energy is used for regeneration. This paper presents the outcome of a solid desiccant evaporative cooling system (DEC) that can be used in moderate humid climates by coupling desiccant dehumidification equipment to evaporative coolers. Silica gel is used as desiccant in the present system. The rates of cooling and dehumidification were assessed under the effects of variables such as air temperature and humidity. The constructed solid desiccant cooling system could reduce the outlet air temperature up to a maximum of 9°C and the relative humidity of the room also decreases gradually. Keywords: Evaporative cooling, solid desiccant, desiccant cooling, relative humidity improvement was made in this system by using desiccant solution . The more important factors for human comfort are temperature and humidity. Cooling is necessary for comfort, also at high humidity our body sweats and we feel discomfort . Evaporative cooling is a process that reduces air temperature by evaporating water of the air stream. As water evaporates, energy is lost from the air causing its temperature to drop. Latent heat describes the amount of heat that is needed to evaporate the liquid; this heat comes from the liquid itself and the surrounding gas and surfaces. When considering water evaporating into air, the wet bulb depression is a measure of the potential for evaporative cooling. This technology has proven to be efficient in arid climates. The main drawback of evaporative cooling is - it is only effective for comfortable cooling in dry climates. When outdoor humidity rises, the cooling capability of evaporative systems declines unless occupants are willing to suffer with high humidity. One way to make evaporative cooling systems which function effectively in hot, humid climates is to add a desiccant pretreatment to the process. The desiccant dehumidifies the air before its temperature is reduced by evaporative cooling. Desiccant cooling systems are rapidly becoming established technology in most parts of the world. This growth has been brought about by the contribution of refrigerants used in conventional cooling systems to the depletion of the ozone layer. Also, the contribution towards global
1. Introduction The energy demand for air-conditioning to provide temperature and humidity control has increased continuously throughout the last decades and is still rising. This increase is found both, in commercial and residential buildings and is largely caused by increased thermal loads, residents’ comfort demands, and architectural trends. Since most of the air-conditioning systems are electrically driven vapor compression machines, the increase is responsible for a large rise in electricity demand and especially high peak loads. The...
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