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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 9146C This will occur when the straight line connecting the states of the two streams on the psychometric chart crosses the saturation line. 9147C Yes. 9148 Two airstreams are mixed steadily. The specific humidity, the relative humidity, the drybulb 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 A33) 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. 924, 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 9149 Two airstreams are mixed steadily. The specific humidity, the relative humidity, the drybulb 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 988 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.
 Spring '08
 Chung

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