S-ST-1-9 A Stepwise Procedure for Determining Tubeside Heat Transfer Coefficients

W. J. Marner and J. W. Palen

A computer-oriented stepwise procedure to determine tubeside heat transfer coefficients is presented. The assumptions made in the analysis are stated, a mathematical model of the problem is formulated, and a detailed outline of the entire procedure is given. An approximate expression for the local heat transfer coefficient in terms of the average coefficient, which provides the basis for the HTRI stepwise procedure, is derived in detail.

In order to illustrate the usefulness of the method and to indicate the type of information which may be obtained from a stepwise analysis, several examples are presented. The results for these examples are obtained using the procedure presently used in HTRI Computer Program ST-4, Mod. 4.0. A number of different flow situations are considered, and both heating and cooling cases are included. The behavior of the local heat transfer coefficient in each example is presented graphically and discussed in detail.

It is clear that in certain situations there can be a substantial difference between the stepwise and average temperature-based heat transfer coefficients. In particular, in those cases where two or three tubeside flow regimes are present, it is strongly recommended that the stepwise method be used. However, if only one tubeside flow regime—laminar, transitional, or turbulent—exists throughout the exchanger, use of the average temperature procedure should prove adequate.