Psychrometrics: Dew-point temp from Relative Humidity

In summary, the problem asks for the dew-point temperature of an air/water vapor mixture at 26C and 45% relative humidity. The equations necessary to solve for the dew-point temperature are Tdp = Tsat, when pg = pv and RH = pv/pg. The solution can be found using the psychrometric chart to obtain the humidity ratio, volume per kg dry air, enthalpy, and Tsat. Alternatively, a more complicated equation can be used as referenced on Wikipedia.
  • #1
mojomike
5
0

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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  • #2
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.
 

1. What is the difference between dew-point temperature and relative humidity?

Dew-point temperature is the temperature at which water vapor in a sample of air will condense into liquid water. Relative humidity is a measure of how much water vapor is present in the air compared to the maximum amount that could be present at a given temperature.

2. How is dew-point temperature calculated from relative humidity?

Dew-point temperature can be calculated from relative humidity using a psychrometric chart or an equation that takes into account the air temperature and relative humidity. This calculation takes into account the relationship between temperature, humidity, and saturation pressure of water vapor in the air.

3. Why is dew-point temperature important for weather forecasting?

Dew-point temperature is important for weather forecasting because it is a more accurate measure of the amount of water vapor in the air compared to relative humidity. It is also useful for predicting the likelihood of precipitation, as air with high relative humidity and a low dew-point temperature is more likely to produce rain or snow.

4. How does dew-point temperature affect human comfort?

Dew-point temperature can affect human comfort by influencing the rate at which sweat evaporates from the skin. A higher dew-point temperature means there is more moisture in the air, making it more difficult for sweat to evaporate and cool the body. This can make hot and humid days feel more uncomfortable.

5. How can dew-point temperature be used in industrial processes?

Dew-point temperature is an important factor in many industrial processes, such as drying, cooling, and refrigeration. It is used to determine the moisture content of air and to control the humidity levels in manufacturing facilities. Dew-point temperature is also used in the production of certain materials, such as pharmaceuticals and semiconductors, to ensure proper moisture levels are maintained.

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