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APPROXIMATE THEORY FOR FILM BOILING ON VERTICAL SURFACES

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1960

Year

Abstract

A new equation is presented for film boiling at a vertical surface for saturated liquids in the absence of forced flow. The principal approximations are that vapor flow near the low end of the heating surface is viscous and Bromely's equation is valid there, turbulence develops where the local Reynolds number reaches about 100, and in the turbulent region of the heating surface thermal resistance is due entirely to the laminar sublayer. Tests with five liquids on tubes having lengths between 2 and 6.3 in., and a range of DELTA T from 200 deg to 780 deg F., show that the equation is reliable to within an average error of about plus or minus 32%. (auth)