Managed to find the humidity ratio

In summary, to determine the specific enthalpy of moist air with values of 760mmHg, 80% relative humidity, and 30 degrees C, one can use a psychometric chart to intercept the temperature and relative humidity and read the corresponding specific enthalpy of 85.25 kJ/kg. Alternatively, the specific enthalpy can be calculated using the equation h=h_{air}+\omega h_{water} with the humidity ratio, \omega, and the specific enthalpies of air and water.
  • #1
TSN79
424
0
Moist air has these values; 760mmHg, 80%, 30 degrees C. I have managed to find the humidity ratio (21,65 g/kg), but how can I determine the specific enthalpy?
 
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  • #2
TSN79 said:
Moist air has these values; 760mmHg, 80%, 30 degrees C. I have managed to find the humidity ratio (21,65 g/kg), but how can I determine the specific enthalpy?

Can you assume the water vapor is at saturation, then look up the enthalpy in a steam table for that temp/press combination?
 
  • #3
No, the answer should be 85.25 kJ/kg, and this value is not in the table for this temp/pressure comb., so there must be some equation in use to figure it out...I guess.
 
  • #4
Use a psychometric chart for water in air (One is presented in " Basic Principles and Calculations in Chemical Engineering" -David Himmelblau ,Fourth Edition- Prentice Hall, Inc. ) and intercept temperature ( 30 C) and relative humidity ( 80 %). Then you read the corresponding specific enthalpy 85. 25 kJ/kg.
 
  • #5
What about if you prove with:

[tex]h=h_{air}+\omega h_{water}[/tex]

where [tex]\omega[/tex] is the humidity ratio?
 

Related to Managed to find the humidity ratio

1. What is humidity ratio?

Humidity ratio is a measure of the amount of water vapor in the air compared to the amount of dry air. It is typically expressed in grams of water vapor per kilogram of dry air.

2. How is humidity ratio calculated?

Humidity ratio is calculated using the following formula: humidity ratio = (mass of water vapor) / (mass of dry air). It can also be calculated using psychrometric charts or online calculators.

3. Why is humidity ratio important?

Humidity ratio is important because it affects the comfort and health of individuals, as well as the performance of certain materials and equipment. It can also impact the formation of clouds and precipitation in the atmosphere.

4. What is a comfortable humidity ratio?

The ideal humidity ratio for human comfort is typically between 0.30-0.60 g/kg, with the exact range varying depending on personal preference and climate. A higher humidity ratio can lead to a feeling of stickiness and discomfort, while a lower humidity ratio can cause dryness and irritation.

5. How is humidity ratio controlled?

Humidity ratio can be controlled through the use of dehumidifiers or humidifiers, which remove or add moisture to the air. It can also be controlled through proper ventilation and air conditioning systems, as well as by limiting activities that release moisture into the air, such as cooking or showering.

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