know how to identify physical situations involving forced convective heat transfer

use empirical correlations to estimate convective heat transfer in fluids flowing under laminar conditions in a pipe

use empirical correlations to estimate convective heat transfer in fluids flowing under turbulent conditions in a pipe

In this module, you will learn about the forced convection heat trasfer. We will observe how to identify real situations where the heat transfer between a solid surface and fluid is due to forced convection. Once we have identified the given situation to be about forced convection, you will learn how to select and use empirical correlations to estimate forced convective heat transfer. These empirical correlations are based on a large number of experiments that were conducted in the mid-20th century in research laboratories under strictly known conditions. The results from those experiments were analyzed and published in dimensionless form for universal applications. In the following video, we will consider fluid flow in a pipe. Note that a fluid can be water or air; in solving a problem, we have to choose correct properties for the given fluid. For fluid flow in a pipe, we will consider three flow conditions, namely laminar, transitional, and turbulent. The empirical correlations to estimate Nusselt number are different for each of the flow conditions. Note that we use the term “estimate,” this is to signify that for each of the correlations we use, it has a certain amount of uncertainty in its result, sometime +/-30%, even with considerable uncertainty, these correlations provide us with useful estimated values for design purposes.

Recap

In this module, you learned how to distinguish situations when heat transfer is due to forced convection. We then considered the flow of a fluid inside a pipe. Depending upon the fluid velocity, the flow could be laminar, transitional, or turbulent. For each case of fluid flow, we considered relevant empirical correlations to determine the Nusselt Number.