When used to dehumidify indoor air, ordinary air-conditioners demand abundant energy and expend it inefficiently. The mechanism of dehumidification on which they rely, the cooling of air to below its dew point to remove moisture by condensation, significantly limits the efficiency, as the air reheats once the moisture is removed. To solve this problem, our group has proposed to use desiccant. The system dehumidifies air using sodium carbonate monohydrate, a chemical that absorbs moisture and changes into decahydrate at low temperature. The compound polyethylene glycol (PEG) is added to the system as a water-transfer medium to increase the contact between the air and sodium carbonate hydrates. In earlier work our group proposed a basic system design and evaluated its efficiency. In doing so, we identified three important points neglected in the design: the power consumption for the circulation pump, the mass transfer characteristics of the spray column, and the hydration reaction rate. In the current study we evaluate a renewed design for the proposed chemical humidity-conditioning system taking these points into account. According to calculations of the system energy balance, the system enables dehumidification with higher COP by 1.5, and practical rates of mass transfer and hydration are expected from the experimental results.

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