Consider the laminar thermal boundary layer development near the entrance of the tube shown in Figure 8.4.

Question:

Consider the laminar thermal boundary layer development near the entrance of the tube shown in Figure 8.4. When the hydrodynamic boundary layer is thin relative to the tube diameter, the inviscid flow region has a uniform velocity that is approximately equal to the mean velocity um. Hence the boundary layer development is similar to what would occur for a flat plate.

(a) Beginning with Equation 7.23, derive an expression for the local Nusselt number NuD, as a function of the Prandtl number Pr and the inverse Graetz number GzD–1. Plot the expression using the coordinates shown in Figure 8.10a for Pr = 0.7.

(b) Beginning with Equation 7.30, derive an expression for the average Nusselt number NuD, as a function of the Prandtl number Pr and the inverse Graetz number GzD–1. Compare your results with the Nusselt number for the combined entrance length in the limit of small x.

Fantastic news! We've Found the answer you've been seeking!

Step by Step Answer:

Related Book For  book-img-for-question

Fundamentals Of Heat And Mass Transfer

ISBN: 9780470501979

7th Edition

Authors: Theodore L. Bergman, Adrienne S. Lavine, Frank P. Incropera, David P. DeWitt

Question Posted: