흡수식 냉동기용 유하액막식 증발기의 전열관 형상이 열전달 성능에 미치는 영향

Abstract

To understand the mechanism and obtain data that can be used for design, an experimental apparatus was constructed to investigate the heat transfer characteristics of a falling film evaporator for an absorption chiller. Evaporators with plain tubes or three enhanced tubes were prepared. The enhanced tubes were designed to improve surface wetting rate with surface protrusions or a floral pattern shape. The performance change of the evaporator was investigated according to the flow rate of chilled water, the inlet temperature of the chilled water, the liquid film Reynolds number, and the evaporation temperature. In the case of using the enhanced tube, the average heat transfer rate was approximately 16.3% higher than that of the plain tube, and the difference in heat transfer rate between the enhanced tubes was as small as approximately 6%. The Nusselt number of end-cross, end-dimple, and end-dimple floral tubes was higher by 13.1%, 26.5%, and 46.9%, respectively, than in the plain tube.