IIR document

Limiting heat and mass transfer mechanisms in desiccant wheels.


Desiccant cooling is an environmentally attractive alternative to conventional mechanical airconditioning. The heart of the process is the rotary desiccant wheel which is used to dehumidify air. Recent experimental measurements of wheels with proposed alternative materials at low regeneration temperatures have shown fewer benefits than anticipated based on the material adsorption characteristics. Here a numerical model of a desiccant wheel was used to investigate the specific influence of the desiccant equilibrium moisture adsorption capacity on the overall wheel performance. In addition, the heat of adsorption, moisture diffusion rate and desiccant specific heat capacity were also varied to provide further insight into the limiting heat and mass transfer mechanisms. The results show that: i) at moderate to high face velocity dehumidification of the supply air is limited by the desiccant diffusion kinetics; ii) at low to moderate face velocities, dehumidification of the supply air is limited by carryover of heat from the regeneration stream; iii) increasing the equilibrium moisture content of the wheel gives only marginal improvement over a range of velocities indicating that the isothermal equilibrium moisture storage capacity is not the primary dehumidification performance limitation, and iv) reducing the heat of adsorption gives a greater improvement at lower face velocities (where the wheel operates closer to the point of adsorption equilibrium).

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Pages: 679-687


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  • Original title: Limiting heat and mass transfer mechanisms in desiccant wheels.
  • Record ID : 30001266
  • Languages: English
  • Source: Sources/sinks Alternative to the Outside Air for Heat Pump and Air-conditioning Techniques (Alternative Sources - AS), Padua, Italy, April 5-7, 2011. / International Sorption Heat Pump Conference (ISHPC11), Padua, Italy, April 6-8, 2011.
  • Publication date: 2011/04/06


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