Thermodynamics HW Solutions 857

# Thermodynamics HW Solutions 857 - Chapter 10 Boiling and...

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Chapter 10 Boiling and Condensation 10-80 Saturated refrigerant-134a vapor condenses on the outside of a horizontal tube maintained at a specified temperature. The rate of condensation of the refrigerant is to be determined. Assumptions 1 Steady operating conditions exist. 2 The tube is isothermal. Properties The properties of refrigerant-134a at the saturation temperature of 35 ° C are h fg = 168.2 × 10 3 J/kg and ρ v = 43.41 kg/m 3 . The properties of liquid R-134a at the film temperature of 35 + 25)/2 = 30 ° C are (Table A-10), TT T fs =+ () / sat 2 ( = C W/m. 0808 . 0 C J/kg. 1448 C /s m 10 1590 . 0 / kg/m.s 10 888 . 1 kg/m 1188 2 6 4 3 ° = ° = × = = × = = l pl l l l l l k ρμ ν μ ρ Analysis The modified latent heat of vaporization is J/kg 10 178.0 = C ) 25 C(35 J/kg 1448 0.68 + J/kg 10 2 . 168 ) ( 68 . 0 3 3 sat * × ° ° × × = + = s pl fg fg T T C h h R-134a 35 ° C Condensate 25 ° C D tube = 3 cm L tube = 7 m The heat transfer coefficient for condensation on a single horizontal tube is C W/m 1581 m)
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