Thermodynamics filled in class notes_Part_47

Thermodynamics - • The evaporative cooling process is commonly modeled(with some error as an adiabatic saturation process • These temperatures

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3.4. GAS-VAPOR MIXTURES 101 Here h v 1 was estimated as the saturated vapor value at T = 84 F by interpolating the tables. In the absence of more information regarding the initial vapor state, this estimate is good as any. The value of h l is estimated as the saturated liquid value at T = 70 F . Now ω 1 = 0 . 622 P v 1 P 1 P v 1 , (3.341) P v 1 = P 1 ω 1 0 . 622 + ω 1 , (3.342) = (14 . 7 psia )(0 . 0124895) 0 . 622 + 0 . 0124895 , (3.343) = 0 . 28936 psia. (3.344) For the relative humidity φ 1 = P v 1 P g 1 , (3.345) = 0 . 28936 psia 0 . 584 psia , (3.346) = 0 . 495 . (3.347) 3.4.3 Wet-bulb and dry-bulb temperatures Humidity is often measured with a psychrometer , which has a wet bulb and dry bulb ther- mometer. The dry bulb measures the air temperature. The wet bulb measures the temperature of a water soaked thermometer. If the two temperatures are equal, the air is saturated. If they are diFerent, some of the water on the web bulb evaporates, cooling the wet bulb thermometer.
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Unformatted text preview: • The evaporative cooling process is commonly modeled (with some error) as an adiabatic saturation process. • These temperatures are also in±uenced by non-thermodynamic issues such as heat and mass transfer rates, which induce errors in the device. • Capacitance-based electronic devices are often used as an alternative to the traditional psychrometer. 3.4.4 Psychrometric chart This well-known chart summarizes much of what is important for binary mixtures of air and water, in which the properties depend on three variables, e.g. temperature, pressure, and composition of the mixture. CC BY-NC-ND. 18 November 2011, J. M. Powers. 102 CHAPTER 3. GAS MIXTURES CC BY-NC-ND. 18 November 2011, J. M. Powers....
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This note was uploaded on 11/26/2011 for the course EGN 3381 taught by Professor Park-sou during the Fall '11 term at FSU.

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Thermodynamics - • The evaporative cooling process is commonly modeled(with some error as an adiabatic saturation process • These temperatures

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