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EXPERIMENTAL INVESTIGATIONS ON HYBRID SOLID DESICCANT – VAPOR COMPRESSION AIR-CONDITIONING SYSTEM FOR INDIAN CLIMATE

Authors:
  • Gujarat Technological University - GTU

Abstract

Hybrid solid desiccant-assisted pre-conditioner and split cooling system, which combines merits of moisture removal by rotary dehumidifier and VCR cooling coil for sensible heat removal, is recently developed as a potential alternative to the traditional vapor compression air conditioners. In the present paper, experiments on a hybrid solid desiccant VCR air-conditioning system were carried out for the typical hot and humid North Indian climate. The overall system performance was evaluated based on variations in ambient conditions i.e. temperature and humidity. The dehumidifier effectiveness is evaluated as a function of various inlet conditions. It is found that the hybrid system can achieve a better performance in hot and humid region due to significant reduction in humidity ratio, because of the introduction of desiccant dehumidifier. Key words: COP, dehumidification, regeneration, solid desiccant wheel, vapor compression system.
EXPERIMENTAL INVESTIGATIONS ON HYBRID SOLID DESICCANT
VAPOR COMPRESSION AIR-CONDITIONING SYSTEM FOR INDIAN
CLIMATE
D.B.JANI , MANISH MISHRA, P.K.SAHOO*
Department of Mechanical & Industrial Engineering,
Indian Institute of Technology, Roorkee, 247667, India
E-mail:dbjani@rediffmail.com,mmishfme@iitr.ernet.in,*sahoofme@iitr.ernet.in
ABSTRACT
Hybrid solid desiccant-assisted pre-conditioner and split cooling system, which combines merits of moisture
removal by rotary dehumidifier and VCR cooling coil for sensible heat removal, is recently developed as a
potential alternative to the traditional vapor compression air conditioners. In the present paper, experiments
on a hybrid solid desiccant VCR air-conditioning system were carried out for the typical hot and humid
North Indian climate. The overall system performance was evaluated based on variations in ambient
conditions i.e. temperature and humidity. The dehumidifier effectiveness is evaluated as a function of various
inlet conditions. It is found that the hybrid system can achieve a better performance in hot and humid region
due to significant reduction in humidity ratio, because of the introduction of desiccant dehumidifier.
Key words: COP, dehumidification, regeneration, solid desiccant wheel, vapor compression system.
1. INTRODUCTION
Traditional vapor compression refrigeration air-conditioning systems employ refrigerants which are
environmentally harmful and require high grade electrical energy for its running. Thus, in space cooling
applications, solid desiccant cooling systems are being developed as an alternative to the conventional vapor
compression refrigeration air-conditioners. Solid desiccant cooling systems are heat driven cooling units in
which heat energy is needed to regenerate the rotary desiccant dehumidifier. Desiccant wheel is the main part
of the system which removes humidity from the supply process air. Hot and dry process air is first sensibly
cooled in heat wheel and then in conventional cooling coil of vapor compression refrigeration air-
conditioner. Latent heat load is removed in rotary desiccant dehumidifier while sensible heat load is removed
later in heat wheel and in conventional cooling coil. Thus, solid desiccant cooling systems can take care of
both sensible and latent load of air conditioned space separately as well as of fresh air requirements. These
systems also have the advantage of being powered by waste heat or solar energy which can easily be
obtained from low grade or renewable energy sources. Thus, these hybrid systems can augment to the
amelioration of comfort, energy and cost saving.
Sheridan and Mitchell (1985) have investigated the energy consumption for air conditioning in hot-
humid and hot-dry climates using hybrid desiccant cooling system. They have concluded that the hybrid
cooling system can save more energy in hot-dry climate than that in hot-humid climate. The performance
evaluation of an integrated hybrid desiccant cooling system in terms of the sensitivity of ambient conditions
has been carried out by Worek and Moon (1988). The performance improvement in hybrid desiccant cooling
system was found 20-80% higher as compared with the traditional vapor compression refrigeration air-
conditioning system at different ambient temperatures. Yadav and Kaushik (1991) have examined a
simulation study of a hybrid solid desiccant air conditioning system consisting of a solid desiccant wheel and
a conventional vapor compression air conditioner unit. It was found that the hybrid system can have
significant energy saving over a traditional vapor compression refrigeration air-conditioning unit. Further,
Jain and Dhar (1995) have investigated four cycles namely the ventilation cycle, the recirculation cycle, the
Dunkle cycle and the wet surface heat exchangers cycle for different climatic conditions of India. The
influence of the effectiveness of heat exchangers and evaporative coolers on overall system performance has
been evaluated. The performance of the Dunkle cycle was found better compared to recirculation and
ventilation cycles in all climatic conditions. Experiments were carried out by Yadav (1995) showing that the
ICR 2015, August 16 - 22 - Yokohama, Japan
ID:229
... Many experiments were conducted on the conventional air-conditioning system in combination with desiccant and claimed improvement in the system performance (Jani et al. 2015(Jani et al. , 2016a. The latent heat load was taken by the solid desiccant, and the system was operated with the moderate cooling coil temperature to manage the sensible heat load only (Ramzy et al. 2011;Yuan et al. 2008). ...
... Many experiments were conducted on the conventional air-conditioning system in combination with desiccant and claimed improvement in the system performance (Jani et al. 2015(Jani et al. , 2016a. The latent heat load was taken by the solid desiccant, and the system was operated with the moderate cooling coil temperature to manage the sensible heat load only (Ramzy et al. 2011;Yuan et al. 2008). ...
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