Heat Transfer to Water at High Flux Densities With and Without Surface Boiling

Surface coefficients of heat transfer have been obtained at rates of heat flux up to 3 Btu/ (sq in.)(sec) for water flowing in stainless-steel tubes at mass-flow rates up to 5.4 lb per sec-sq in. The nonboiling forced-convection data were correlated by the Colburn equation Nuf = 0.023 Ref0.8Prf1/3 within ±5 per cent, but, with surface boiling, considerably larger Nu moduli were observed. When surface boiling occurred, the wall temperature was determined primarily by the pressure, being relatively insensitive to variations in velocity, heat flux, and bulk temperature. The maximum heat flux that could be removed under given conditions was limited by an unsteady-flow phenomenon. Data for pressure drop with and without nonboiling heat transfer are presented and correlated by an empirical viscosity correction factor.