Heat loss from bare steel pipes wet vs dry 1

[Fixertedd]

Is there a reference that quantifies the heat loss from bare steel pipe when wet? Like outdoor pipelines in the rain or cold pipes that get condensation on the outside?

 

[1503-44]

Sure. A constant ambient temperature at the surface of the pipe material is the typical assumption.
Whether that is the evaporation or condensation temperature, or any other temperature isn't too important, other than mataining evaporation requires that the latent heat of evaporation be available (such heat is usually extracted from pipe contents) in order to keep the wet substance evaporating, rather than just dripping off. Likewise, if the water is condensing, the pipe surface will be at a constant temperature and an additional heat of condensation is usually transferred to the contents of the pipe. For any given moisture content of the ambient surrounding air, the condensation, or evaporation temperature can be calculated. To make it easier, one or the other temperature is used assuming saturated ambient air, as those are more well known temperatures and also describe the limiting condition. The effect of a particular ambient air temperature at a given velocity can also be calculated. See Prandtl and Grashoff coefficients to include effects of air or other fluid circulatiing around the pipe.

If the ambient air can be supplied in sufficient quantity at constant temperature, without heating or cooling from pipe contents, you're done. If the ambient conditions are affected by pipe contents temperature, it becomes more complicated and you get into a heat exchanger calculation.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."