# #27 in 6 Minute HVAC PM



## Yingli (Oct 20, 2009)

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


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## JoeysVee (Oct 20, 2009)

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


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## Yingli (Oct 20, 2009)

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


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