Experimental Study on a Process Design for Adsorption Desiccant Cooling Driven with a Low-Temperature Heat

Abstract

Among the desiccant cooling process, 2-rotor process consisting of a honeycomb rotor dehumidifier and a sensible heat exchanger is the mainstream of the cooling processes which are practically applied to supermarket, hospital and so on. Most of them are driven with a higher regeneration temperature around 100–140∘C obtained from gas-engine heat pump or micro gas turbine generator. However, dehumidifying performance of this typical configuration driven with a low temperature heat is not sufficient for cooling at higher ambient humidity. In this study, 4-rotor desiccant cooling process equipped with a double stage dehumidification was proposed and investigated experimentally. In this process, regeneration temperature around 70∘C could produce a sufficient dehumidifying performance at high ambient humidity. Furthermore, the cascade use of hot water inside the cooling cycle was applied and confirmed somewhat lower cooling performance than that operated with parallel supply of hot water. Against this result, COPr of the former was much higher than that of the latter. Effect of water spray evaporative cooling at the inlet of regeneration air stream on the process performance was also investigated. This evaporative cooling was expected to cause humidity increase in regeneration air reducing the dehumidifying performance of the honeycomb absorber, while the evaporative cooling plays an important role to produce a lower temperature in supply air. Experimental results showed that the amount of dehumidified water at the process without water spray evaporative cooler was actually larger than that of process with water spray evaporative cooler. This behavior was due to increase of humidity or relative humidity in the regeneration air as expected. However, temperature of supply air produced by the process with evaporator was rather lower than that of the other, resulting higher COP value. It was concluded that the evaporative cooler effectively worked at higher regeneration temperature and lower ambient humidity.