Abstract
Empirical/semi-empirical correlations are available in the literature to quantify the effect of several major parameters, like bulk pressure, non-condensable gas mass fraction, and wall subcooling, on condensation heat transfer coefficient (HTC). However, despite numerous applications of condensation on inclined flat plates, there is a lack of understanding of the effect of surface inclination on condensation heat transfer. Accordingly, a dedicated experimental program was undertaken to investigate the effect of surface inclination angle on filmwise steam condensation. Experiments were performed at different bulk pressures (1.7–4.2 bar absolute) and steam-air mass fractions (ranging from pure steam, i.e., 0% to 40% w/w air), with the steam-air mixture flowing over a flat test plate (Re range, 4200–4800). In each run, the inclination angle of the test surface was varied from −90 deg (condensation underneath the horizontal surface, facing downward) to +90 deg (condensation over the horizontal surface, facing upward) in increments of 15–20 deg (inclination angle θ measured from vertical). The results reveal an intriguing trend: for pure steam condensation, the HTCs decrease as the plate is inclined in either direction from the vertical, and the variation is nearly symmetric for both upward- and downward-facing configurations. On the other hand, for steam condensation in the presence of air, the HTCs decrease monotonically for upward-facing configurations, while they increase slightly (10–20%), and decrease subsequently (for θ < −70 deg) for downward-facing cases. Finally, the HTCs for inclined orientations are compared with the HTC in the standard vertical configuration to quantify the effect of inclination angle.
Experimental investigation of the influence of the Pitot tube diameter on measurements of pressure distribution in flat supersonic microjets
