# Managed to find the humidity ratio

1. Oct 18, 2004

### TSN79

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? :grumpy:

2. Oct 18, 2004

### geometer

Can you assume the water vapor is at saturation, then look up the enthalpy in a steam table for that temp/press combination?

3. Oct 18, 2004

### TSN79

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. Oct 18, 2004

### Iraides Belandria

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. Oct 19, 2004

### Clausius2

What about if you prove with:

$$h=h_{air}+\omega h_{water}$$

where $$\omega$$ is the humidity ratio?