Joule-Thomson effect TEP

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Hilary Gibbs
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Joule-homson effect EP elted oics el gs; intrinsic energy; Gy-Lussc theory; throttling; n der Wls eqution; n der Wls force; inverse Joule- homson effect; inversion temerture.

1 Joule-homson effect EP elted oics el gs; intrinsic energy; Gy-Lussc theory; throttling; n der Wls eqution; n der Wls force; inverse Joule- homson effect; inversion temerture. Princile A strem of gs is fed to throttling oint, where the gs (O or N ) undergoes ditic exnsion. he differences in temerture estlished etween the two sides of the throttle oint re mesured t vrious ressures nd the Joule- homson coefficients of the gses in question re clculted. Equiment Joule-homson rtus emerture meter digitl, emerture roe, immers. ye educing vlve for O / He educing vlve f. nitrogen Wrench for steel cylinders Steel cylinder rck, moile Steel cylinder, O, 0 l, full Steel cylinder, nitrogen, 0 l, full Fig. : Exerimentl set-u: Joule-homson effect. P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen

2 EP Joule-homson effect sks. Determintion of the Joule-homson coefficient of O.. Determintion of the Joule-homson coefficient of N. Set-u nd rocedure he set-u of the exeriment is s in Fig.. If necessry, screw the reducing vlves onto the steel cylinders nd check the tightness of the min vlves. Secure the steel cylinders in their loction. Attch the P-tuing etween the reducing vlve nd the Joule-homson rtus with hose tue clis. On ech side of the glss cylinder, introduce temerture roe u to few millimetres from the frit nd ttch with the union nut. onnect the temerture roe on the ressure side to inlet nd the temerture roe on the unressurised side to inlet of the temerture mesurement rtus. Imortnt: he exerimenting room nd the exerimentl rtus must e in therml equilirium t the strt of the mesurement. he exerimentl rtus should e ket out of direct sunlight nd other sources of heting or cooling. Set the temerture mesurement rtus t temerture difference mesurement. emerture meter should e switched on t lest 30 min efore erforming the exeriment to void therml drift. ed oerting instructions for further exlntions of the temerture meter. Oen the vlves in the following order: steel cylinder vlve, oerting vlve, reducing vlve, so tht n initil ressure of 00 kp is estlished. educe the ressure to zero in stges, in ech cse reding off the temerture difference one minute fter the rticulr ressure hs een estlished. Perform the mesurement for oth gses, nd determine the tmosheric ressure nd mient temerture. heory nd evlution he stte for rel gses is given y the vn der Wls eqution. ( ) where is the ressure, the molr volume nd the temerture of the gs. is the universl gs constnt, nd re the chrcteristic n der Wls coefficients of the gs. he dditionl ressure y intermoleculr forces of ttrction is descried y, reresents the volume of molecules. In rel gses the intrinsic energy is comosed of thermocinetic nd otentionl comonent. he totl chnge of the intrinsic energy of rel gs therefore deends not only on the temerture nd the molr het of gs ut lso on the volume. he otentil energy / in the gs is given y the work ginst the intermoleculr forces. P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen

3 Joule-homson effect EP the totl differentil of the intrinsic energy is given y with nd d d d for 0 for 0 Fig. : hrottling nd the Joule-homson effect. P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen 3

4 4 P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen Joule-homson effect EP Fig. 3: emerture differences mesured t vrious rm ressures. if the totl differentil is sustituted through differences, you get with for 0 nd for 0 he exnsion of the gs t the throttle-oint is ditic ( Q 0). If externl het losses nd friction during the flow of the gs re excluded, the totl energy H of the rocess is constnt. H For further clcultions ressure cn e sustituted y using vn der Wls eqution. H he reltionshi etween n is given y the totl differentil of this eqution ( ) H ( ) H H 0 ecuse H is constnt. For the next ste is neclected ginst. he molr het t constnt volume should e relced y the molr het t constnt ressure. his could e done roximtely y the eqution for idel gses. hen At the throttle oint ressure grdient nd temerture grdient re estlished. his effect is nmed the Joule homson effect nd is descried y the coefficient

5 Joule-homson effect EP o get this coefficient, the difference hs to e chnged into. his could e done roximtely y the eqution for idel gses. y differentition n sustitute totl differentils y differences gin you get ( ) he Joule homson coefficient is then In rel gses, the intrinsic energy is comosed of thermokinetic content nd otentil energy content: the otentil of the intermoleculr forces of ttrction. his is negtive nd tends towrds zero s the moleculr distnce increses. In rel gses, the intrinsic energy is therefore function of the volume, nd: > 0 During ditic exnsion ( Q 0), during which lso no externl work is done, the overll intrinsic energy remins unchnged, with the result tht the otentil energy increses t the exense of the thermokinetic content nd the gs cools. At the throttle oint, the effect nmed fter Joule-homson is qusi-sttionry rocess. A sttionry ressure grdient is estlished t the throttle oint. If externl het losses nd friction during the flow of the gs re excluded, then for the totl energy H, which consists of the intrinsic energy nd dislcement work : H H In this eqution, or is the work erformed y n imginry iston during the flow of smll mount of gs y chnge in osition from osition to or osition 3 to 4 (see Figure ). In rel gses, the dislcement work does not equl the dislcement work ; in this cse: < P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen 5

6 EP Joule-homson effect his mens tht, from the moleculr interction otentil, dislcement work is ermnently done nd removed: > or > he Joule-homson effect is descried quntittively y the coefficients For chnge in the volume of n der Wls gs, the chnge in intrinsic energy is nd the Joule-homson coefficient is thus DW c In this eqution, coefficients. If the exnsion coefficients re inserted, then c is the secific het under constnt ressure, nd nd re the n der Wls α ( const) 0 dw α. c he mesurement vlues in Fig. 3 give the stright line grdients nd O N (.084 ± 0.050) 0 ( 0.53 ± ) P P he two temerture roes my give different solute vlues for the sme temerture. his is no rolem, s only the temerture difference is imortnt for the determintion Joule-homson coefficients. 6 P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen

7 Joule-homson effect EP he literture vlues re O t 0 nd 0 5 ir.6 0 P, P t 0 nd 0 5 P. For O, with 3.60 P m 6 /mol 4.7 cm 3 /mol c 366. J/mol the n der Wls eqution gives the coefficient, dw O 5 P For ir, with.40 P m 6 /mol 39. cm 3 /mol c 88.9 J/mol the n der Wls eqution gives the coefficient dw, ir 5 emrks he formul for the Joule homson coefficient gives the condition for cooling rocess: i is the inversion temerture. If < 0 the temerture hs to e lower then i to cool gs with the rocess: < 0 nd < i then < 0 For ir (N ) or O cooling is oserved t room temertur. H or He hve ositive coefficient t room temerture, for H this cn e hzrdous ecuse self ignition is ossile. P30600 PHYWE series of ulictions Lortory Exeriments Physics PHYWE SYSEME GMBH & o. G D Göttingen 7

Thermodynamics. Joule-Thomson effect Ideal and Real Gases. What you need: Complete Equipment Set, Manual on CD-ROM included

Thermodynamics. Joule-Thomson effect Ideal and Real Gases. What you need: Complete Equipment Set, Manual on CD-ROM included Ideal Real Gases Thermodynamics 30600 What you can learn about Real gas Intrinsic energy Gay-Lussac theory Throttling Van der Waals equation Van der Waals force Inverse Inversion temperature Principle: