HVAC 6-minute /Problem 27

[mandileng]

In problem 27 (Hvac 6-min) , how did he found the slop 1163.9 ??? I can't get it by delt h at (70 db , 20 rh )- 50 dew point .

 

[Mike M PE]

The slope comes from the Steam tables in the back of MERM for steam at 29.7 psia. It's the slope because the air will follow water temperature.

 

[vesterholt]

I found this confusing at first as well based on what is on the chart Delta h / Delta Humidity. However, it is as simple as just using the enthalpy of the steam. Think of it this way, if you add one pound of steam to the air, you are adding 1163.9 BTU AND One pound of moisture. So Enthalpy goes up by 1163.9 and moisture goes up by 1 lb, hence the slope is 1163.9/1 = 1163.9.