Experimental pressure profiles along the vapor channel of a flat-plate heat pipe

An experimental flat-plate heat pipe with an adiabatic top plate has been constructed to study the vapor flow. The heat pipe is operated around 15 C with water as the working fluid. Longitudinal pressure profiles in the rectangular vapor channel have been measured for values of the radial Reynolds number of 3.7, 5.7, and 6.6. The profiles agree well with those predicted with a simple Poiseuille flow approximation model that is based on the assumption of parabolic velocity profiles for the vapor flow. Still better agreement is found with the results obtained by using the computer program TEACH that predicts for the complete heat pipe a 10% larger total pressure drop than does the simple model for a radial Reynolds number of 5. For radial Re greater than 5, pressure buildup in the condensation zone is found as predicted.