Development of innovative and high-efficiency air conditioning system using chemical humidity conditioning

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The largest problem of today's air conditioning system is the dehumidification. Conventional air conditioning needs cooling down to dew point, and when target temperature is only 19℃, cooling down to 5℃ is needed, which results in low system efficiency. To circumvent this problem, we proposed a high-efficiency chemical humidity conditioning system where sodium carbonate decahydrate suspended in inert solvent is employed, and fundamental dehumidification characteristics were determined. First, we prepared slurry by suspending sodium carbonate decahydrate in n-pentanol, checked the fundamental reaction to proceed, and reaction rate was determined. In parallel, screening of the solvent was conducted, and considering price, safety, smell, and other characteristics, polyethylene glycol was found to be suitable for our purpose. Repetitive reaction was conducted for the sodium carbonate slurry in polyethylene glycol, and it was found that complete dehydration to monohydrate results in decrease in reactivity, but that dehydration leaving some decahydrate maintained reactivity, leading to stable repetition of hydration and dehydration. In addition, equilibrium water concentration for hydration/dehydration was determined for the slurry using polyethylene glycol. The water vapor pressure over polyethylene glycol-water mixture was measured, and parameters of UNIQUAC equation were determined. Hydration rate, that directly determines the process performance, was measured, and the rate equation was determined so that theoretical minimum volume for dehumidification of kitchen was calculated. For demonstration purpose, suspended bubble column reactor was built and dehumidification experiment was conducted with changing air flow rate and solid concentration. From the result, it was found that rate determining step was mass transfer of water vapor from gas phase to liquid phase.