Cylinder Pressurization and Temperature

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dhanramesh2002 Member Join Date: Dec 2009 Posts: 6	Cylinder Pressurization and Temperature 12/14/2009 11:43 AM
	2 cylinders are available with me. Both are interconnected through hose and control valve. First cylinder contains helium gas at 300bar at ambient temperature. Second cylinder is empty. Now I am pressurizing the second cylinder form the first cylinder by opening the valve at a charge rate of 2bar / minute. Now if I measure the 2^nd cylinder wall temperature it reads more than the Helium gas temperature inside the 2^nd cylinder. How is it possible?
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standarded Guru Join Date: Mar 2008 Location: Southeast US of A Posts: 555 Good Answers: 50	#1 Re: Cylinder Pressurization and Temperature 12/14/2009 11:54 PM
	Is this a homework problem? __________________ Speak softly and carry a big stick.
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simonsd Power-User Join Date: Nov 2008 Location: Port Glasgow, Free Republic of Scotland Posts: 360 Good Answers: 30	#2 Re: Cylinder Pressurization and Temperature 12/15/2009 4:44 AM
	It does sound like it doesnt it. So the obscure answer is The temperature is higher because thatit wahat entropy and enthalpy of the situation demand Hope that helps reverse JT would be my guess __________________ Free advice guaranteed or your money back
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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: 32175 Good Answers: 839	#3 Re: Cylinder Pressurization and Temperature 12/15/2009 4:51 AM
	Google "the Joule-Thompson expansion effect". __________________ "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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Keith E Bowers Power-User Join Date: Jan 2007 Location: Houston,Texas Posts: 378 Good Answers: 24	#4 Re: Cylinder Pressurization and Temperature 12/15/2009 11:11 AM
	This is a standard 'problem' in Advanced Thermodynamics' in Chemical Engineering class. The helium (at ambient temp) cools when it expands across the control valve due to the"Joule Thompson" effect. Every gas has a unique JT coefficient, which has been experimentally determined. (Note that hydrogen has a 'reverse' JT coefficient, meaning it heats up as it expands.) The (now cooled) helium enters the No 2 Cylinder (which is at ambient temp at the start of this exercise). Thus, the gas temperature is lower than the cylinder temperature. If one ponders things, note that if you close the control valve at the instant the pressures in each cylinder match, the two cylinders will be at different temperatures and contain different masses of helium, and when both return to ambient temperature, will have different measured pressure! __________________ Keith E Bowers, PMP
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kavoshgar Active Contributor Join Date: Nov 2009 Posts: 14	#5 Re: Cylinder Pressurization and Temperature 12/16/2009 1:01 PM
	I agree with keith E Bowers. His reply is perfect. __________________ KAVOSH
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