Laminar free convection from a horizontal semi-circular cylinder to power-law fluids
- 作者：Avinash Chandra ; R.P. Chhabra ; chhabra@iitk.ac.in
- 关键词：Semi-circular cylinder ; Free convection ; Power-law fluid ; Grashof number ; Prandtl number ; Nusselt number
- 刊名：International Journal of Heat and Mass Transfer
- 出版年：2012
- 期刊代码：42_00179310
- 类别：ce
- 出版时间：May, 2012
- 卷：55
- 期：11-12
- 页码：2934-2944
- 文件大小：1959 K
摘要
Extensive numerical results on the flow and thermal fields are presented for free convection from a semi-circular cylinder (flat base upward) immersed in quiescent power-law fluids for the following ranges of conditions: Grashof number, 10 猢?#xA0;Gr 猢?#xA0;105, Prandtl number, 0.72 猢?#xA0;Pr 猢?#xA0;100, and power-law index, 0.2 猢?#xA0;n 猢?#xA0;1.8. The heat transfer characteristics are analyzed in terms of the isotherm patterns, local and average Nusselt number as functions of the pertinent dimensionless parameters. The flow field is visualized in terms of the streamline patterns adjacent to the surface of the cylinder for a range of values of the Grashof number, Prandtl number and power-law index. A separated flow region forms at as low values of the Prandtl number as Pr = 0.72 for n 猢?#xA0;1 (Newtonian and shear-thickening fluids); whereas for shear-thinning fluids (n < 1), the flow remains attached to the cylinder surface over the range of conditions encompassed here. The bubble size grows with Grashof number and it shrinks with Prandtl number. In order to quantify the deviation from the Newtonian behaviour, the normalized values of average Nusselt number are analyzed as a function of the power-law index. In addition, a correlation is proposed for average Nusselt number as a function of the Grashof number, Prandtl number and power-law index. In general terms, shear-thinning fluid behaviour enhances heat transfer whereas shear-thickening has adverse influence on it.