EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER AND PRESSURE DROP CHARACTERISTICS FOR VERTICAL DOWNFLOW USING TRADITIONAL AND 3D-PRINTED MINI TUBES

In this study, an investigation on the influences of different manufacturing techniques heat transfer and pressure drop in developing fully developed regions mini-tube under flow regimes is introduced. The purpose research to experimentally investigate characteristics using 3D-printed tubes traditional stainless steel vertical direction isothermal non-isothermal boundary conditions. Experiments are conducted distilled water (Prandtl numbers varying from 4 7) at Reynolds 800-10000 with fluxes between 30 500 kW·m<sup>-2</sup>. Test inside diameters 2 mm used, average surface roughness 1.6 μm 15.3 μm, respectively. results compared previous studies. It verified that almost same for tube laminar region. deviation these two 7.7%. However, turbulent region, Nusselt region increases by 45% as a tube. friction factors heating conditions also increased 209%. addition, enters transition earlier. show critical number around 2300 2000, Correlations predict coefficients good accuracy.