Topics: HVAC, Water vapor, Water Pages: 23 (5898 words) Published: August 28, 2013
International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol:13 No:01


Application of Evaporative Air Coolers Coupled With Solar Water Heater for Dehumidification of Indoor Air A S Alosaimy
Mechanical Engineering Department, Faculty of Engineering, Taif University, KSA Abstract -- In the present work, novel configuration of solar powered desiccant dehumidification system is investigated. The proposed system comprises two evaporative air coolers. One of the two coolers functions as an absorber and the second, which is coupled with solar water heater, functions as a desiccant regenerator. In the experimental part of this investigation, Calcium Chloride is regenerated using solar energy. Hot water from a solar collector is circulated through an air heater to regenerate the liquid desiccant. Mathematical model, which can be applied for analysis of the proposed system, is developed. Absorption-regeneration cycle for the dehumidifier is described and analyzed. An expression for the efficiency of the simple cycle is introduced. Theoretical analysis shows that strong and weak solution concentration limits play a decisive role in the value of cycle efficiency. S ystem efficiency with consideration of heat and work added to the system is well defined. The limits of regeneration temperature and mass of strong solution per kg of produced vapor are found highly dependent on the operating concentration of desiccant. Experimental results show that solution with 30% concentration can be regenerated up to 50% using solar energy. Good agreement is found between the trained data of the ANN model and the experimental measurements for the whole range of the air inlet temperature.

Index Term--

Desiccant; humidification; absorption; air conditioning; Calcium chloride.

1. INTRODUCTION In hot and humid areas ,interest in utilizing solar poweredcooling systems for air-conditioning and refrigeration purposes has been growing continuously. Being considered as one path towards more sustainable energy systems, solar-cooling is comprised of many attractive features . This technology can efficiently serve large latent loads and greatly improve indoor air quality by allowing more ventilation wh ile t ightly controlling humidity [1]. On the other hand, solar-powered air conditioning has seen renewed interest in recent years due to the growing awareness of environmental problems such as global warming [2,3]. Solar collector/regenerator (C/R) systems can achieve liquid regeneration at lower temperatures which is suitable for buildings with high outdoor air requirements in high humidity areas [4,5]. Several solar-driven refrigeration systems

have been proposed and most of them are economically justified. These systems include sorption systems containing liquid/vapor or solid/vapor absorption/adsorption, vapor compression systems, and hybrid desiccant vapor compression systems [6]. The regenerator is one of the key components in liquid desiccant air-conditioning systems, in wh ich desiccant is concentrated and can be reused in the system. The heat required for regenerating the weak desiccant solution is supplied into the regenerator by either hot air or hot desiccant solution. This heat can be provided by any form of low-grade thermal energy which is suitable for solar thermal applications. Different regenerator designs have been examined and a variety of theoretical models have been employed to analyze the regeneration process [7-9]. An analytical procedure for calculating the mass of water evaporated from the weak solution in the regenerator in terms of climatic conditions and solution properties at the regenerator inlet has been developed by Kakabayev and Khandurdyev[1].Alizadeh and Saman [10] developed a computer model using Calciu m Chloride as the working desiccant to study the thermal performance of a forced parallel flo w solar regenerator. A parametric analysis of the system has been performed...

References: [1] [2] [3] [4] [5] [6] [7] [8] [9] A. Kakabaev, A. Khandurdyev, Absorption solar refrigeration unit with open regeneration of Solution, Gliotekhnika (in Russian) 5(4) (1969) 2832. R. Yang, P.L. Wang, Experimental study of a forced convection solar collector/regenerator for open cycle absorption cooling, Trans. ASME J Solar Energy Engineering 116 (1994) 194-199. G. Grossman, Solar-powered systems for cooling, dehumidification and air-conditioning, Solar Energy 72(1) (2002) 53–62. M. Krause, W. Saman, K. Vajen, Open cycle liquid desiccant air conditioning systems-Theoretical and experimental investigations, in: Proceeding of the ANZSES Conference, Dunedin, New Zealand, 2005. K. Daou, R.Z. Wang, Z.Z. Xia, Desiccant cooling air conditioning: a review, Renewable and Sustainable Energy Reviews 10 (2006) 55-77. J.R.KDieckmann, J. Brodrick, Liquid Desiccant Air Conditioners, ASHRA Journal, October 2008. R. Yang, W.J. Yan, Simulation study for an open-cycle absorption solarcooling system operated in a humid area, Energy 17(7) (1992) 649-655. A.A. Aly, E.B. Zeidan, A.M. Hamed, Performance evaluation of opencycle solar regenerator using artificial neural network technique, Energy and Buildings 43 (2011) 454–457. R. Yang, P.L. Wang, A simulation study of the performance evaluation of single-glazed and double-glazed collectors/regenerators for an opencycle absorption solar cooling system, Solar energy 71(4) (2001) 263268. A. Alizadeh, W. Saman, Modeling and performance of a forced flow solar collector/regenerator using liquid desiccant, Solar Energy 72(2) (2002) 143-154. R.M. Lazzarin, F. Castellotti, A new heat pump desiccant dehumidifier for supermarket application, Energy and Buildings 39 (2007) 59–65 E. Hurdogana, O. Buyukalaca, T. Yılmaz and A. Hepbasl, Experimental investigation of a novel desiccant cooling system, Energy and Buildings 42 (2010) 2049–2060. X. Niu, F. Xiao, G. Ge, Performance analysis of liquid desiccant based air-conditioning system under variable fresh air ratios, Energy and Buildings 42 (2010) 2457–2464. Hamed AM and Alosaimy AS. Modeling and Simulation of Desiccant Operated Humidity Pump (DOHP).Int. J. of Thermal & Environmental Engineering. Volume 4, No. 1 (2012) 39-45.
[15] Hamed AM. Absorption–regeneration cycle for production of water from air-theoretical approach. Renewable Energy Journal 19(2000) 625–35. [16] A.S.Alosaimy and A.M Hamed, Theoretical and Experimental Investigation on theApplication of Solar Water Heater Coupled with Air Humidifier for Regeneration of Liquid Desiccant. Energy 36 (2011) 3992-4001. [17] A. S. Alosaimy, A. M. Hamed, A. M. El-Kersh and A. A. Aly, Application Of Solar Energy For Air Conditioning In Humid Zones, Final Report, Taif University, 2010. [18] E.Z. Zaetsev, G.G. Aseev, Physical-chemical properties of binary nonorganic solutions, Khemia, Leningrad, USSR, 1988.
NOMENCLAT URES Ca Carnot factor, dimensionless Cp specific heat, J/kg.oC h enthalpy, J/kg H total equivalent heat, W L latent heat of evaporation of water, J/kg m mass flow rate of evaporated water during regeneration, kg/s M mass flow rate of desiccant kg/s p vapour pressure, mmHg q heat added to vapour, W Q heat added, W t ambient temperature, o C T desiccant temperature, K X desiccant mass concentration GREEK SYMBOLS   efficiency relative humidity
Subscripts a b d cyc e o r s sys v condition at the end of absorption bed desiccant cycle equivalent initial, inlet condition at the end of regeneration saturation condition system vapor
[10] [11] [12] [13] [14]
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