Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum Feb 16th 2015, 05:24 PM #1 Junior Member   Join Date: Feb 2015 Posts: 2 Enthalpy-thermo problem Hi, I have a practice problem in thermo that I have some difficulties with: The PVT relation for helium is given by the following equation of state: P=RT/V-b, where b=2.3*10^5 m^3/mol Through an isenthalpic (H=0) throttling process, the gas is let to expand from a pressure of 10^8 Pa at 300 K to a pressure of 10^5 Pa. Calculate the final temperature of the gas. Cp canbe considered constant at a value of 5/2R. I started by using the eq. for enthalpy dH=0=CpdT + (V-T(dV/dT))dP and finding (dV/dT) from the PVT relation given which resulting in R/P Replacing R/P in the dH eq. we get: 0=CpdT + (V-T(R/P))dP Wouldn't this cancel the dP term since TR/P =V. Or should I not cancel them and just integrate? I'm a bit confused and could use some help. Thank you in advance    Feb 17th 2015, 09:31 AM #2 Senior Member   Join Date: Jun 2010 Location: NC Posts: 417 Hi, Looks like you have the answer... Having 0=CpdT + (V-T(R/P))dP and P=RT/V-b or TR/p = V-b Then 0=CpdT + b dP So integrate this. TSH for PHF   Feb 22nd 2015, 05:22 PM #3 Junior Member   Join Date: Feb 2015 Posts: 2 Thank you   Tags enthalpy, enthalpythermo, equation of state, problem, thermodynamics Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Davidvia0 Advanced Thermodynamics 5 Jan 2nd 2016 02:11 PM zijincheng Advanced Thermodynamics 4 Jun 19th 2015 10:26 AM Gav33 Advanced Thermodynamics 2 May 21st 2014 03:01 PM rimmer Thermodynamics and Fluid Mechanics 1 Mar 9th 2010 03:54 AM Natla Energy and Work 0 Nov 6th 2008 04:19 PM