Thermodynamics HW Solutions 842

Thermodynamics HW Solutions 842 - Chapter 10 Boiling and...

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Chapter 10 Boiling and Condensation 10-58 Saturated refrigerant-134a vapor condenses inside a horizontal tube maintained at a uniform temperature. The fraction of the refrigerant that will condense at the end of the tube is to be determined. Assumptions 1 Steady operating conditions exist. 2 The tube is isothermal. 3 The vapor velocity is low so that Re vapor < 35,000. Properties The properties of refrigerant-134a at the saturation temperature of 30 ° C are h fg = 173.1 × 10 3 J/kg and ρ v = 37.53 kg/m 3 . The properties of liquid R-134a at the film temperature of 20)/2 = 25 ° C are (Table A-10) TT T fs =+ () / sat 2 ( = 30 + C W/m. 08325 . 0 C J/kg. 1427 C /s m 10 1667 . 0 / kg/m.s 10 2.012 kg/m 1207 2 6 4 3 ° = ° = × = = × = = l pl l l l l l k ρμ ν μ ρ Analysis The heat transfer coefficient for condensation inside horizontal tubes is R-134a 30 ° C ondensate 20 ° C C W/m 2 . 509 C 0) 2 C)(30 J/kg 1427 ( 8 3 + J/kg 10 1 . 173 C 0) 2 s)(30 kg/m 10 012 . 2 ( C) W/m 08325 . 0 )( kg/m ) 53 . 37 1207 )( kg/m 1207 )( m/s 81 . 9 ( 555 . 0 ) ( 8 3 ) ( ) ( 555 . 0 2 4 / 1 3 4 3 3 3 2 4 / 1 sat sat 3 internal ° = ° ° × × ° × ° = + = = s pl fg s l l
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