The Dittus-Boelter equation should be only used when the temperature difference between the fluid and wall surface is not large by evaluating all fluid properties

at the bulk mean fluid temperature.

But when the variation in properties is large due to a large temperature difference, the

Seider and Tate equation should be used as follows:

Note: Preference should given to Gnielinski equation over Seider and Tate equation.

The Dittus-Boelter equation should be only used when the temperature difference between the fluid and wall surface is not large by evaluating all fluid properties

at the bulk mean fluid temperature.

But when the variation in properties is large due to a large temperature difference, the

Seider and Tate equation should be used as follows:

Note: Preference should given to Gnielinski equation over Seider and Tate equation.