Convection Coefficient

Getting h is the hard part of every real thermal problem. Conduction is a material property you look up and radiation is geometry, but convection depends on the flow — so the honest answer is always a correlation. Used outside their valid range these do not fail loudly, they return a plausible wrong number, so the range check is reported alongside every result.

Evaluate fluid properties at the film temperature (surface + fluid)/2 for external flow, and at the bulk mean temperature for internal flow — pick the preset nearest that, not nearest the surface temperature. Correlations of this kind carry roughly ±20–25% uncertainty even used correctly, so treat h as a band, not a number. Once you have h, feed it to Pipe Insulation, Fin Efficiency or Heat Exchanger NTU.