The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?

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D-0.2. The Sieder-Tate correlation is Nu = 0.8 Re^0.8 Pr^(1/3) (k_bulk/k_fluid)^0.14. Since Re is proportional to D and the heat transfer coefficient h is proportional to Nu/(Re*Pr), the dependence on D is generally found to be weak, often approximated as D^-0.2.