Introduction to Convective Heat Transfer

11Turbulent Internal Flow: Momentum and Heat Transfer

11.1 Introduction

A common problem encountered by engineers is the heat transfer to turbulent fluid flow in a tube. This may occur in heat exchangers, boilers, condensers, evaporators, etc. For this reason, it is useful to know how to estimate the heat transfer coefficient. We will study fully developed turbulent momentum and heat transfer for internal flows in this chapter. Many engineering devices have elements made up of uniform cross section. Flows in uniform channels are the simplest turbulent motions. After a development period, the mean flow and turbulence remain the same at successive sections; then, the flow is said to be fully developed. Experimental studies for friction factor and heat transfer coefficient indicate that momentum transfer and heat transfer are fairly insensitive to the geometry for fully turbulent flow in internal flow systems having uniform cross section. For this reason, the analysis of forced convection heat transfer for fully developed turbulent flow will be presented in the context of parallel plate channel and circular pipe systems. The experimental measurements of turbulent flows in smooth pipes indicate that the near wall velocity profiles of flat plates can be used in internal flows. In other words, the turbulence structure of turbulent flow in the inner region (region very close to tube wall) of the tube wall is essentially identical to the turbulent flow along a flat plate. This means ...