Thermal and Hydrodynamic Phenomena in a Horizontal, Uniformly Heated Steam-Generating Pipe

Abstract

This study is aimed at elucidating the relationship between the hydrodynamic and thermal phenomena in horizontal boiler tubes. It focuses on the empirical evaluation of the wall temperature distribution in a uniformly heated, 6-m-long, water-carrying pipe, operated at near-atmospheric pressure, over a range of imposed heat fluxes and water flow rates. The results reveal the existence of a complex temperature field on the pipe wall, incorporating circumferentially isothermal and anisothermal regions and a significant axial variation along the top of the pipe. For moderate flow rates these variations were found to give rise to two distinct anisothermal zones: a low-quality zone near the inlet and a moderate-quality zone approximately midway along the pipe. Physical models and semi-analytic relations for the liquid and vapor velocities, constituting the boundaries between isothermal and anisothermal operation, are presented.