Quote:
Originally Posted by aerohead
... My data came from Psychrometric tables which are for 29.92" Hg and 59-Degree F...
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Hi Aerohead,
Ahh, now we know where part of the difference in our numbers came from...
Our STP (Standard Temperature and Pressure) at work is considered 29.92 inHg and 70°F. This is what most air flow calibration labs in the U.S. use nowadays.
I remember some 30 years ago or so, 60°F used to come up when dealing with the 'official' height/density of water columns when measuring inches of water pressure, which is about 1/13th of one inch of mercury.
If one were to use 60°F instead of 70°F then the equation looks like:
= (460°R + 60°F) / (460°R + (-20°F))
= (520°R) / (440°R)
= 18.2%
So now we can see that your psychrometric table gives essentially the same response as simply considering the absolute temperature ratio.
Jim.