Energy and exergy analyses of an experimental open-cycle desiccant cooling system.

Abstract A procedure is developed for the energy and exergy analyses of open-cycle desiccant cooling systems and it is applied to an experimental unit operating in ventilation mode with natural zeolite as the desiccant. The same procedure and formulations may easily be applied to the units operating in recirculation mode. Energy-based performance parameters such as the coefficient of performance (COP) of the unit and the effectiveness’ of system components are presented. Exergy destruction and exergy efficiency relations for the system and its components as well as the reversible COP of the system are derived. The energy and exergy formulations are applied to the experimental unit using the data collected during a typical operation of the unit. The unit has a COP of 0.35, a reversible COP of 3.11, and an exergy efficiency of 11.1%. Desiccant wheel has the greatest percentage of total exergy destruction with 33.8% followed by the heating system with 31.2%. Rotary regenerator and evaporative coolers account for the remaining exergy destructions. The analysis shows that an exergy analysis can provide useful information with respect to the theoretical upper limit of the system performance, which cannot be obtained from an energy analysis alone. The analysis allows us to identify and quantify the sites with the losses of exergy, and therefore showing the direction for the minimization of exergy losses to approach the reversible COP.

[1]  Akio Kodama,et al.  Entropic analysis of adsorption open cycles for air conditioning. Part 2: interpretation of experimental data , 2000 .

[2]  Z. Lavan,et al.  Second Law Analysis of Desiccant Cooling Systems , 1982 .

[3]  Y. Çengel,et al.  Thermodynamics : An Engineering Approach , 1989 .

[4]  W. M. Worek,et al.  The second-law analysis of a recirculation cycle desiccant cooling system: Cosorption of water vapor and carbon dioxide , 1996 .

[5]  Clive B. Beggs,et al.  The potential for solar powered single-stage desiccant cooling in southern Europe , 2002 .

[6]  M. Mobedi,et al.  Adsorption in Energy Storage , 1989 .

[7]  S. A. Sherif,et al.  A feasibility study of a solar desiccant air-conditioning system—Part I: psychrometrics and analysis of the conditioned zone , 1999 .

[8]  Richard A. Gaggioli,et al.  Available Energy and Exergy , 1998 .

[9]  Mehmet Kanoglu,et al.  Exergy analysis of multistage cascade refrigeration cycle used for natural gas liquefaction , 2002 .

[10]  S. Srinivasa Murthy,et al.  Experiments on a silica gel rotary dehumidifier , 1989 .

[11]  Michael J. Moran,et al.  Availability analysis: A guide to efficient energy use , 1982 .

[12]  Adrian Bejan,et al.  Theory of heat transfer-irreversible refrigeration plants , 1989 .

[13]  S. Farooq,et al.  Numerical Simulation of a Desiccant Bed for Solar Air Conditioning Applications , 1991 .

[14]  John W. Mitchell,et al.  Second Law Analysis of Solid Desiccant Rotary Dehumidifiers , 1988 .

[15]  William A. Beckman,et al.  Open-cycle desiccant air conditioning as an alternative to vapor compression cooling in residential applications , 1984 .

[16]  Akio Kodama,et al.  Entropic analysis of adsorption open cycles for air conditioning. Part 1 : first and second law analyses , 2000 .

[17]  Mehmet Kanoglu,et al.  Exergy analysis of vapor compression refrigeration systems , 2002 .

[18]  Clive B. Beggs,et al.  The use of solar desiccant cooling in the UK: a feasibility study , 2002 .

[19]  I. L. Maclaine-cross.  High-Performance Adiabatic Desiccant Open-Cooling Cycles , 1985 .

[20]  S. C. Kaushik,et al.  Experimental studies on the dehumidifier and regenerator of a liquid desiccant cooling system , 2000 .

[21]  Akio Kodama,et al.  Experimental Study of Optimal Operation for a Honeycomb Adsorber Operated with Thermal Swing , 1993 .

[22]  A. Bejan.  Advanced Engineering Thermodynamics , 1988 .

[23]  John W. Mitchell,et al.  The Use of Dehumidifiers in Desiccant Cooling and Dehumidification Systems , 1986 .

[24]  S. A. Sherif,et al.  A feasibility study of a solar desiccant air-conditioning system. Part II : Transient simulation and economics , 1999 .