A study on the development of the velocity and temperature fields in a laminar flow through an eccentric annular ducts

偏心된 二重圓管의 環狀部를 지니는 層流流動에서의 連度場 및 溫度場의 確立에 대한 硏究

A numerical study has been conducted on the development of the velocity and temperature fields in a laminar flow through an eccentric annular duct. A bipolar coordinates system is adopted, and a numerical program is developed to analyze 3-dimensional parabolic flow problems. In the analysis of the velocity field, the entrance length has been defined as the distance where the axial pressure gradient is greater than that of the developed velocity field by 5%. The dimensionless hydrodynamic entry length increases with increasing eccentricity. In the transverse flow fields, the reverse flow region along the wall due to the developing axial velocity near the entrance of the duct is found. In the analysis of the temperature field, the thermal entry length has been defined as the axial distance where the mean fluid temperature is 5% less than that of the developed temperature field. The dimensionless thermal entry length increases as eccentricity or Prandtl number increases. The overshoot of the mean Nusselt number over the developed value at the zero-temperature wall is encountered, and the rate of the overshoot increases with the increase of the eccentricity and Prandtl number.

본 연구에서는 동시확립문제의 속도장해석에 있어서 단면내의 속도분포에 대 한 일체의 가정을 하지 않고 운동량방정식을 직접 해석하여 단면내의 속도분포를 구하 였다. 또한 Prandtl수, 반경비 및 편심도가 열전달특성에 미치는 영향에 대한 해석 도 수행하였다.