Subscripts act actual (din atmospheric c coolant 13 bundle 1) based on diameter cf effective f liquid phase fl flooded region /" finned region fs fin sides f(fin tips V vapor phase 11 based on hydraulic diameter L per unit length N row number o outer li row r fin root, or refrigerant s tube surface sat saturation sli shear ts test section tut total tw tube wall xxvi u f unfinned region water 1 row 1 Diniensionless groups Nu Nusselt number, {liD)/k P* forced convection parameter defined by Equation 2.30 Ph Phase change number, CpATji Pr Prandtl number, (fiCp) I k Re Reynolds number, 47u/(jD/i) Re two-phase Reynolds number, (Uqq pjD)/i^ij Xf i Lockhart-Martinelli parameter, defined by Equation 2.37