How can one estimate how the friction factor changes in heat exchanger tubes with a change in temperature?

How can one estimate how the friction factor changes in heat exchanger tubes with a change in  temperature?
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Answer :

Seider and Tate recommended the following for determine friction factors inside heat exchanger tubes  with varying temperatures: First, determine the average, bulk mean temperature in the processing line.  For example if the fluid enters the line at 300 °C and leaves at 280 °C, use 290 °C to determine the  physical properties and friction factors. As for corrections: Laminar Flow If the liquid is cooling, the  friction factor obtained from the mean temperature and bulk properties is divided by (bulk  viscosity/wall viscosity)0.23 and for heating, it’s divided by (bulk viscosity/wall viscosity)0.38. Here, the  bulk and wall viscosity are determined at the mean temperature over the length of the line. Turbulent  Flow If the liquid is cooling, the friction factor obtained from the mean temperature and bulk properties  is divided by (bulk viscosity/wall viscosity)0.11 and for heating, it’s divided by (bulk viscosity/wall  viscosity)0.17.
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