Experimental laminar falling film heat transfer coefficients on a large diameter horizontal tube

A test rig was designed and fabricated to measure local heat transfer coefficients from a large‐diameter, steam‐heated horizontal tube to thin falling films of water. The results of the experiments generally support the theory developed by Rogers for laminar film conditions, which were found to persist up to film Reynolds numbers of about 2000. Agreement between theoretical predictions of heat transfer coefficients and the measured values is reasonable for the thermal boundary layer development region, but measured values are about 20% lower than predicted values in the developed region. The lower values in the developed region are attributed mainly to measured film thicknesses being greater than predicted values.