How Does One Measure Enthalpy?

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Dug Associate Join Date: May 2011 Posts: 27 Good Answers: 3	How Does One Measure Enthalpy? 05/19/2011 10:12 AM
	I want to measure the efficiency of a fan or air compressor. Reply#1 of http://cr4.globalspec.com/thread/31413/Centrifugal-Air-Compressor-Efficiency-Calculation provides a formula and states that all required information can be measured. I can measure most of the terms required except enthalpy, so how does one measure enthalpy?
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	Pathfinder Tags: Compressor efficiency enthalpy fan formula

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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 31071 Good Answers: 826	#1 Re: How does one measure enthalpy? 05/19/2011 10:15 AM
	One looks it up in tables. Try "Thermodynamic Properties of Fluids" by Mayhew & Rogers, or just about any ASHRAE psychrometric chart. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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Dug Associate Join Date: May 2011 Posts: 27 Good Answers: 3	#2 In reply to #1 Re: How does one measure enthalpy? 05/19/2011 12:02 PM
	I conclude then that one does not measure enthalpy directly. Instead one will need to measure a dry bulb temperature and then also a wet bulb temperature (to determine % Relative Humidity). If the the inlet air pressure to a fan or air compressor is at sea level then I can use a sea level Psychometric Chart, but for discharge enthalpy, where the discharge air pressure is somewhat variable (it would depend on the actual discharge air pressure) then I would need to find (if one exists) a psychrometric chart that has pressure as a variable, and a high enough pressure value for the outlet of an air compressor.
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