Chemical Engineering

A numerical study to determine the influence of axial wall conduction on forced convection heat transfer in an externally finned pipe has been made. The effects of wall conductivity, interfin spacing, and external heat transfer coefficient are examined by comparing the results with the corresponding solutions obtained assuming negligible wall conduction. Results indicate that the axial conduction in the pipe walls has a significant influence on the heat transfer behavior. The bulk temperature or the heat transferred to the fluid is underestimated when wall conduction is ignored. At high wall conductivity values, the wall temperatures and Nusselt numbers exhibit a monotonic variation in the axial direction, with the behavior becoming increasingly nonmonotonic as the wall conductivity value is decreased.

ABSTRACT: The effect of the cross-sectional shape on the steady flow of a Newtonian fluid in long tubes under an electromagnetic force is explored. A general method of analysis is presented, which draws on previous results of the authors in the study of flow in tubes of arbitrary contours. The velocity field is determined and analyzed for a variety of cross-sectional shapes that include the triangle, square and others. These results aim, in part, at providing a basis for the investigation of more complex flows, such as magnetorheological flows, in tubes of non-circular shapes. Such flows are important in many applications as related to damping devices and others where controlled modulation of resistance forces is desired.