#27 in 6 Minute HVAC PM

[Yingli]

hello

Could someone explain how to get delta h /delta w= 1164 slop,e ratio of enthalpy to humidity ? The hg at 15psig is 1163.9 Btu/lbm, but how the hg become a ratio of enthalpy to humidity?

Thank you very much.

Yingli

 

[JoeysVee]

Look at the protractor on the top left hand corner of the ASHRAE psych chart and you'll see the delta h/delta w.

 

[Yingli]

thank you, I still can not get it as 1164, please let me know which point on the half circle that I need to draw a line from pointat 70 f db and 20% relative humidty?

yingli