Journal of the Korean Solar Energy Society (한국태양에너지학회 논문집)

The Korean Solar Energy Society (한국태양에너지학회)
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Research on the Heat Transfer and Pressure Drop by Installation Conditions of Rectangular Obstacle in a Solar Air Heater Based on CFD

CFD를 활용한 태양열 공기가열기 내 사각저항체 설치 조건에 따른 열전달 및 압력강하에 관한 연구

  • Choi, Hwi-Ung (Graduate School of Refrigeration and Air-conditioning Engineering, Pukyong National University) ;
  • Kim, Young-Bok (Dept. of Mechanical System Engineering, Pukyong National University) ;
  • Son, Chang-Hyo (Dept. of Refrigeration and Air-conditioning Engineering, Pukyong National University) ;
  • Yoon, Jung-In (Dept. of Refrigeration and Air-conditioning Engineering, Pukyong National University) ;
  • Choi, Kwang-Hwan (Dept. of Refrigeration and Air-conditioning Engineering, Pukyong National University)
  • 최휘웅 (부경대학교 냉동공조공학과 대학원) ;
  • 김영복 (부경대학교 기계시스템공학과) ;
  • 손창효 (부경대학교 냉동공조공학과) ;
  • 윤정인 (부경대학교 냉동공조공학과) ;
  • 최광환 (부경대학교 냉동공조공학과)
  • Received : 2019.01.14
  • Accepted : 2019.02.11
  • Published : 2019.02.28
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Abstract

The solar air heater has various performances according to an obstacle installed in the air duct. Many studies on thermal performance have been conducted. But many of these studies were using a kind of rib type obstacle attached at the bottom of absorbing plate, but they are so hard to be manufactured. In this study, characteristics of the heat transfer and pressure drop in the solar air heater with various horizontal rectangular obstacles was investigated by CFD (Computational Fluid Dynamics) analysis. As a result, the heat transfer performance was improved from 1.2 to 3.32 times depending on installation conditions of rectangular obstacle. The pressure drop, however, also increased with increment of heat transfer performance from 2.8 to 180 times only by changing installation conditions of rectangular obstacle. Thus, the performance factor presenting the thermal performance enhancement on the same pressure drop was also confirmed. As a result, the highest value of 0.828 as better performance factor was obtained at the lower height of rectangular obstacle and this value has started to decrease with increment of heat transfer performance. In the end, it could be confirmed that the pressure drop was carried higher than the quantity of improvement of the heat transfer performance when the heat transfer performance was increased by change of installation conditions of rectangular obstacle. Both heat transfer enhancement and pressure drop to be required for system need to be considered before the rectangular obstacles are applied to the solar air heater.

Keywords

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Fig. 1 Schematic view of solar air heater with rectangular obstacle

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Fig. 2 Computational domain and boundary conditions for smooth duct

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Fig. 3 Geometric condition of rectangular obstacle

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Fig. 4 Comparison between simulation results and Dittus-Boelter equation

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Fig. 5 Nusselt number with respect to installation conditions of rectangular obstacle

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Fig. 6 Velocity vector with respect to installation conditions of rectangular obstacle

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Fig. 7 Friction factor with respect to installation conditions of rectangular obstacle

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Fig. 8 Pressure contour with respect to installation conditions of rectangular obstacle

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Fig. 9 Performance factor with respect to installation conditions of rectangular obstacle

Table 1 Simulation conditions

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Table 2 Pressure drop with respect to installation conditions of rectangular obstacle

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