Psychrometrics: Dew-point temp from Relative Humidity

AI Thread Summary
To determine the dew-point temperature from a given air/water vapor mixture at 26°C and 45% relative humidity, the key relationship is that the dew-point temperature (Tdp) equals the saturation temperature (Tsat) when the partial pressure of water vapor (pv) equals the saturation pressure (pg). Using a psychrometric chart, one can derive the humidity ratio, volume per kg of dry air, and enthalpy. The discussion highlights that while the problem may seem straightforward, it was not covered in the contributor's thermodynamics class. A complex equation for calculating dew point is referenced from Wikipedia, suggesting that having all necessary variables allows for direct calculation. Understanding these relationships is crucial for solving similar problems, especially for the FE exam preparation.
mojomike
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Homework Statement



Air/Water vapor mixture, at 26C and 45%RH.
What is the Dew-point temperature


Homework Equations



Tdp = Tsat when pg=pv
RH = pv/pg


The Attempt at a Solution



From the psychrometric chart I can get the Humidity ratio, volume per kg dry air, Enthalpy, and Tsat.

I hope what I've collected here can count toward an "attempt" at a solution. This is not homework. It is a practice problem for the FE exam. This was never covered in my thermo class. I'm sure it is simple, but it is escaping me now. thanks for any help you can provide.
 
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There is a fairly complicated equation on wikipedia for dew point. http://en.wikipedia.org/wiki/Dew_point

If you have all the variables you can just plug and chug. I don't know if that formula is in your FE reference book or not though.
 
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