Ito Takehiro

Two-phase boundary-layer treatment of forced-convection film boiling

Abstract With the well-known boundary-layer theory as a basis, a theoretical study has been made of film-boiling heat transfer from an isothermal vertical plate to a subcooled stagnant liquid. The results are also applicable to film-boiling heat transfer from an isothermal horizontal cylinder. By assuming a thin stable vapor film, the boundary-layer equations were transformed into a system of ordinary differential equations by the similarity relations, and the heat-transfer characteristics were found to be correlated by six parameters. The formulation of the two-phase flow problem in this paper differed from that by Sparrow and Cess, only in that nonslip conditions of interfacial velocity and shearing stress were required, instead of the zero interfacial-velocity condition used by them. We first obtained solutions for some arbitrarily chosen sets of parameters to see how each parameter affected the heat-transfer rate, this proved Sparrow and Cesss evaluation of the effects of subcooling on heat-transfer coefficient to be wrong. Then we found the heat-transfer characteristics of water at 1 atm. Differential equations were solved on electronic digital computers by successive approximation.

Pool film boiling heat transfer from a horizontal cylinder to saturated liquids

Abstract Referring to free convective film boiling heat transfer from a horizontal cylinder, many kinds of correlations of heat transfer have been proposed. However, none of them correlates the available data for a wide range of kind of the boiling liquid, the diameter of the cylinder, the degree of superheat and the system pressure. The integral method of boundary layer was applied to solve the equation of momentum and that of energy for this problem, taking into account of the inertia force in the former and the convective term in the latter and two nondimensional parameters were derived from this analysis. By employing these parameters, a semi-theoretical correlating equation accurate enough for practice over a wide range of parameters was proposed.