Chapter 10 Boiling and Condensation10-48E Saturated steam at a saturation temperature of Tsat= 95°F condenses on the outer surfaces of 20 horizontal pipes which are maintained at 85°F by circulating cooling water and arranged in a rectangular array of 4 pipes high and 5 pipes wide. The rate of heat transfer to the cooling water and the rate of condensation per unit length of the pipes are to be determined. Assumptions1Steady operating conditions exist.2The pipes are isothermal. PropertiesThe properties of water at the saturation temperature of 95°F are hfg= 1040 Btu/lbm and ρv= 0.0025 lbm/ft3. The properties of liquid water at the film temperature of TTTfs=+=()/sat2(95 + 85)/2 = 90°F are (Table A-9E), ρμνμlllllpllk==⋅==°⋅°621218420 02965099903583../...lbm / ftlbm / ft hft / hC Btu/lbmFBtu / h ft F2Steam95°F...................85°FCondensate flow 4 tubes ×8 tubes AnalysisThe modified latent heat of vaporization is hhCfgfgpls*.()(.=+−=×⋅°−°06810400 99985satBtu / lbm + 0.68Btu / lbm F)(95) F = 1047 Btu / lbmThe heat transfer coefficient for condensation on a single horizontal pipe is FftBtu/h1942ft)F(1/12
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