Dynamic Characteristics of Thermal Stratification Build-up by Unsteady Natural Convection

비정상 자연대류에 의한 온도성층화의 동특성에 관한 연구

  • 강보선 (한국과학기술원 기계공학부) ;
  • 이준식 (서울대학교 공과대학 기계공학과) ;
  • 이택식 (서울대학교 공과대학 기계공학과) ;
  • 노승탁 (서울대학교 공과대학 기계공학과)
  • Published : 1988.08.01

Abstract

Dynamic characteristics of thermally-forced stratification process in a square enclosure with a linear temperature profile at the side walls have been investigated through flow visualization experiment and numerical analysis. The experiment was performed on air with the Rayleigh numbers of order $10^5$. A particle tracer method is used for the flow visualization and to obtain a sudden linear temperature profile at the side walls copper blocks which already have a linear temperature profile are come into contact with the thin copper plates of the test section. Immediately a meridional circulation is developed and heat transfer takes place from the wall to the interior region by circulation of fluid and finally a thermal stratification is achieved. In the numerical study, QUICK scheme for convective terms, SIMPLE algorithm for pressure correction, and the implicit method for the time marching are adopted for the integration of conservation equations. Comparison of flow visualization and numerical results shows that the developing flow patterns are very similar in dynamic nature even though there is a time lag due to the inevitable time delay in setting up a linear temperature profile. For high Rayleigh numbers, the oscillatory motion is likely to take place and stratified region is extended. However, initial temperature adjustment process is much slower than that for low Rayleigh numbers.

Keywords

Acknowledgement

Grant : 태양열에 의한 냉방 및 난방시스템의 성능 향상

Supported by : 학술진흥재단