열전달 향상 장치에 따른 평판형 태양열 집열기의 압력강하 및 열전달 특성
Pressure drop and heat transfer characteristics of a flat-plate solar collector with heat transfer enhancement device
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초록
평판형 태양열 집열기의 효율을 높이기 위한 방법으로 열전달 향상 장치의 삽입, 표면 거칠기의변화 등 다양한 방법들이 알려져 있다. 본 연구는 실험을 통해 다양한 열전달 향상 장치를 제작하고 이를 덕트에 삽입해 실험을 수행하였다. 실험은 기본적으로 덕트 윗 평판에 일정한 열유속을 가하였고, 삽입된 모델은 매끈한 덕트 형상(Base case)과 Chamfered rib 10°, Chamfered rib 20°, Rib & Groove, Rib &Dimple 모델이다. 실험은 Reynolds 수가 2,300∼22,000의 범위에서 이루어졌으며 이는 난류영역에 해당한다. 열전달 향상 장치를 삽입하면 면적의 증가와 2차 유동으로 인하여 열전달이 향상되고, Reynolds 수가 증가할수록 열전달이 향상되었으며 압력강하도 증가하였다. 열전달 측면에서는 Rib & Dimple 모델이열전달 향상 효과가 가장 좋았으며, 압력강하는 Chamfered rib 10° 모델이 가장 낮았으며, 성능계수 측면에서도 Chamfered rib 10° 모델이 가장 높은 것으로 나타났다.
Abstract
The surface roughness and heat transfer enhancement devices are known to increase the performance of a flat plate soar collector. This study includes the experiments on the effect of the several heat transfer enhancement devices inserted in duct to simulate the flat-plate solar collector. Experiment was basically at a constant heat flux on the upper duct wall. Inserted heat transfer enhancement devices are Chamfered rib 10°,Chamfered rib 20°, Rib & Groove and Rib & Dimple. Reynolds number is in the range of 2,300 to 22,000which corresponds to turbulent regime. With the heat transfer enhancement devices, heat transfer would increase by the secondary flow and the increase of the heat transfer area. Pressure drop also increases with the insertion of the enhancement devices. Rib & Dimple model is the best in heat transfer enhancement, however,Chamfered rib 10° model is the lowest in the pressure drop. Considering the heat transfer enhancement simultaneously with low pressure drop increase, performance factor was the best for the Chamfered rib 10°.
참고문헌 (10)
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