FTFS Chap09 P146 - P = 95 kPa AIR 1 2 3 25 m 3 /min 12 C...

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Unformatted text preview: P = 95 kPa AIR 1 2 3 25 m 3 /min 12 C 90% 32 C 40% 20 m 3 /min 3 3 T 3 Chapter 9 Gas Mixtures and Psychrometrics Adiabatic Mixing of Airstreams 9-146C This will occur when the straight line connecting the states of the two streams on the psychometric chart crosses the saturation line. 9-147C Yes. 9-148 Two airstreams are mixed steadily. The specific humidity, the relative humidity, the dry-bulb temperature, and the volume flow rate of the mixture are to be determined. Assumptions 1 Steady operating conditions exist 2 Dry air and water vapor are ideal gases. 3 The kinetic and potential energy changes are negligible. 4 The mixing section is adiabatic. Properties Properties of each inlet stream are determined from the psychometric chart (Figure A-33) to be air dry /kg m 882 . air dry O/kg H kg 0119 . air dry kJ/kg 7 . 62 3 1 2 1 1 = = = v h and air dry /kg m 819 . air dry O/kg H kg 0079 . air dry kJ/kg 9 . 31 3 2 2 2 2 = = = v h Analysis The mass flow rate of dry air in each stream is kg/min 5 . 30 air dry kg / m 819 . min / m 25 kg/min 7 . 22 air dry kg / m 882 . min / m 20 3 3 2 2 2 3 3 1 1 1 = = = = = = v V m v V m a a From the conservation of mass, ( . . ) . m m m a a a 3 1 2 227 305 532 = + = + = kg / min kg / min Specific humidity and the enthalpy of the mixture can be determined from Eqs. 9-24, which are obtained by combining the conservation of mass and energy equations for the adiabatic mixing of two streams: 7 . 62 9 . 31 0119 . 0079 . 5 . 30 7 . 22 3 3 3 3 1 3 3 2 1 3 3 2 2 1-- =-- =-- =-- = h h h h h h m m a a which yields, 3 3 kJ / kg dry air = = 0.0096 kg H O / kg dry air 2 h 450 . These two properties fix the state of the mixture. Other properties of the mixture are determined from the psychometric chart: air dry /kg m 845 . 3 3 3 3 = = = v T 63.4% C 20.6 Finally, the volume flow rate of the mixture is determined from /min m 45.0 3 = = = kg) / m .845 kg/min)(0 2 . 53 ( 3 3 3 3 v m V a 9-149 Two airstreams are mixed steadily. The specific humidity, the relative humidity, the dry-bulb temperature, and the volume flow rate of the mixture are to be determined. Assumptions 1 Steady operating conditions exist 2 Dry air and water vapor are ideal gases. 3 The kinetic and potential energy changes are negligible. 4 The mixing section is adiabatic. Analysis The properties of each inlet stream are determined to be 9-88 P = 1 atm AIR 1 2 3 25 m 3 /min 12 C 90% 32 C 40% 20 m 3 /min 3 3 T 3 Chapter 9 Gas Mixtures and Psychrometrics air dry kJ/kg 9 . 64 kJ/kg) 559.9 (0.0128)(2 + C) C)(32 kJ/kg 005 . 1 ( air dry O/kg H kg 0.0128 kPa ) 92 . 1 (95 kPa) 92 . 1 ( 622 ....
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This homework help was uploaded on 04/18/2008 for the course EML 3007 taught by Professor Chung during the Spring '08 term at University of Florida.

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FTFS Chap09 P146 - P = 95 kPa AIR 1 2 3 25 m 3 /min 12 C...

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