• 한국태양에너지학회 논문집
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• 제35권4호
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• pp.43-55
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• 2015

This paper presents the thermal hydraulic performance of a three dimensional rib-roughened solar air heater (SAH) duct with the one principal wall subjected to uniform heat flux. The SAH duct has aspect ratio of 12.0 and the Reynolds number ranges from 2000 to 12000. The roughness has relative rib height of 0.045, ratio of dimple depth to print diameter of 0.5 and rib pitch ratio of 8.0. The flow attack angle is varied from $35^{\circ}$ to $70^{\circ}$. Various turbulent flow models are used for the heat transfer and fluid flow analysis and their results are compared with the experimental results for smooth surfaces. The computational fluid dynamics (CFD) results based on the renormalization k-epsilon model are in better outcomes compared with the experimental data. This model is used to calculate heat transfer and fluid flow in SAH duct with the compound roughness of V-shaped ribs and dimples. The overall thermal performance based on equal pumping power is found to be the highest (2.18) for flow attack angle of $55^{\circ}$. The thermo-hydraulic performance for V-pattern shaped ribs combined with dimple ribs is higher than that for dimple rib shape and V-pattern rib shape air duct.

• 동력기계공학회지
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• 제9권2호
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• pp.88-92
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• 2005

The experiment of thermal performance about closed-wet cooling tower was conducted in this study. A closed cooling tower is a device similar to a general cooling tower, but with cooling tower replaced by a heat exchanger. The test section for this experiment has the process that the cooling water flows from the top of the heat exchanger to the bottom side in the inner part of the tube, and spray water flows in the gravitational direction in the outer side. Air comes in direct contact with the spray water at the outer side of the tube while passing from the lower the upper part having a counterflow to the spray water. The heat transfer pipe used in this experiment is a bare-type tube having an outer diameter of 15.88mm. The heat exchanger is consisted of seven rows and fifteen columns. In this experiment, thermal performance of the cooling tower is derived from overall heat transfer coefficients between the process fluid and sprayed water and volumetric overall mass transfer coefficient between sprayed water and air.

• 태양에너지
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• 제19권3호
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• pp.23-28
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• 1999

본 논문에서는 난방용 축열보드에 응용하기 위해서 미세캡슐을 함유한 축열블럭의 열성능 특성을 조사하였다. 상변화 물질인 $CH_3COONa{\cdot}3H_2O$를 미세캡슐 형태로 제조하였고 미세캡슐 함유량이 각각 10%, 20%가 되도록 시멘트 몰타르와 혼합하여 축열블럭을 제작하였다. 축열블럭의 축열 및 방열 특성을 분석하기 위하여 유량과 유입 냉각 온도를 변화시켰다. 실험결과를 보면 미세캡슐 함유량이 증가할 수록 블럭에 축열되는 축열량은 증가를 하였고 방열시간도 증가를 하였다. 그리고 방열과정시 유량이 증가하고 유입 냉각온도가 감소함에 따라 방열시간은 감소하였다. 순수블럭(0% 미세캡슐 함유량)은 방열과정시 총괄 열전달 계수는 시간에 따라서 일정하게 유지를 하지만 축열블럭에서는 시간이 지남에 따라 증가를 하였다.