Theoretical and experimental study on heat and mass transfer of a porous ceramic tube type indirect evaporative cooler

摘要

The wettability characteristic of wet channels plays an important role in cooling performance of an indirect evaporative cooler (IEC). To improve its wettability, porous ceramic is used as a novel material for IEC. The porous structure provides hydrophilic feature and water storage capacity. Therefore, the wet-bulb efficiency of the cooler can be improved because of higher wettability and larger specific surface area. This paper presents a theoretical and experimental study on a tubular porous ceramic IEC. The mathematical model of heat and mass transfer was established and numerically solved to evaluate its cooling performance. The influence of various structural parameters and operational parameters of porous ceramic IEC are analyzed, including the tube length, tube spacing, wall thickness, wet-bulb temperature depression and working/output air volume ratio. The experimental study is also carried out, on one hand, to validate the numerical model; and on the other hand, to optimize the working air/product air flow ratio. The results indicate the optimal tube spacing is 40 mm. The tube length plays a significant effect on the cooling performance of IEC when it is less than 1.5 m. Experimental study shows the optimal performance of porous ceramic IEC prototype is achieved under the product air velocity of 3.4 m/s, working air velocity of 4.0 m/s and the working air/product air volume ratio of 0.9.