Method of Measuring the Vapor Pressure and Concentration of Fluids using VLE and Vibrating Tube Densitometer Apparatuses

Transcription

1 Method of Measurng the Vapor Pressure and Concentraton of Fluds usng VLE and Vbratng Tube Denstometer Apparatuses Momn Elhad Abdalla Assstant Professor,Chemcal Engneerng Department, Unversty of Khartoum; Sudan Sddharth Pannr Purdue Unversty DAAD Deutscher Akademscher Austausch Denst e.v German Academc Exchange Servce July 11-14, 016

2 July 11-14, 016 Purdue Conferences

3 Content 1. Introducton.. Refrgerants and Envronmental Problems. 3. Phase Equlbrum Apparatus. 4. Concentraton Measurement. 5. Thermodynamc Modelng and Smulaton. 6. Results and Dscusson. 7. Concluson and Recommendaton. July 11-14, 016 Purdue Conferences 3

4 1. Introducton: Refrgerant and Applcatons R15a R15a R365mfc R365mfc R15a R365mfc p T July 11-14, 016 Purdue Conferences 4

5 . Refrgerants and Envronmental Problems Most of the Radaton trapped by CFCs, HCFCs and carbon doxde gases n the atmosphere. The GWP s the rato of the warmng caused by a substance X to the warmng caused by a smlar mass of carbon doxde. Sources : [IPCC,EPA,NASA] July 11-14, 016 Purdue Conferences 5

6 . Refrgerants and Envronmental Problems Ozone Depleton Ozone depleton refers to a lowered concentraton of ozone n the upper atmosphere. More UV radaton s reachng the Earth s surface. ODP s the rato of the mpact on ozone caused by a substance X to the mpact on ozone caused by a smlar mass of R11. July 11-14, 016 Purdue Conferences 6

7 . Refrgerants and Envronmental Problems Hgh ODP (Ozone Depleton Potental) Ozone Depleton Problem. Hgh GWP (Global Warmng Potental) Global Warmng Problem. Hydrogen FLAMMABLE TOXIC Chlorne Fluorne LONG ATMOSPHERIC LIFE TIME July 11-14, 016 Purdue Conferences 7

8 . Refrgerants and Envronmental Problems Choce of the Refrgerant. Zero ODP... Low GWP. Envronmental Requrements Low toxcty. v. Low fre rsk (flammablty). Safety Requrements v. Low freezng pont. v. v. v. x. Hgh crtcal temperature. Hgh vapor pressures for the operatng temperature. Chemcal stablty. Low cost. July 11-14, 016 Purdue Conferences 8

9 . Refrgerants and Envronmental Problems Choce of the Refrgerant Choce of the sutable flud (Pure flud and mxture) Example : R134a (GWP=1300) R134a has best solublty on the ol. Prevous works used R134a/R15a Mxture (see. z.b. Int. J.Thermophys. 13(6), 957) R134a snce 011 and accordng to EU Laws s forbdden. In ths work: R15a/R365mfc Mxture R15a (GWP=10, ODP=0) R365mfc (GWP=78, ODP=0) Just a rare work stated n the lterature for the vapor pressure and concentraton of ths mxture. July 11-14, 016 Purdue Conferences 9

10 3. Phase Equlbrum Apparatus Importance of the Phase Equlbrum Measurement Best understand of the phase change for the refrgerant mxture. The phase bevaor s of great mportance durng the desgn of the refrgeraton cycle. The known method for the measurng the phase equlbra: Synthetc Method Sample wth known composton Varaton of the temperature and pressure tll the separaton of the phases. Analytc Method Gven specfed pressure and temperature. Sample unt for the specfed phases after reachng the equlbra. R15a R15a R365mfc R365mfc R365mfc R15a p T July 11-14, 016 Purdue Conferences 10

11 3. Phase Equlbrum Apparatus M T Temperature 7 T p Pressure 1 Equlbrum Cell M 4 Mxer 1 3 Crculatng Pump 4 Quck Samplng Valve T p 5 5 Samplng U-Tube 6 Heat Exchanger Thermostat (solaton) 8 Vbratng Tube Denstometer Zusammensetzungsanalyse Concentraton Analyss 8 DMA July 11-14, 016 Purdue Conferences 11

12 3. Phase Equlbrum Apparatus/Temperature Measurement The temperature of the sothermal bath was measured by three thermocouple (Rössel type K) suted at dfferent postons of the thermal bath, and one nserted wth a depth of 3mm at the crculaton lne. The equlbrum cell nternal temperature was montored by a Pt-100Ω (ICS Schneder Messtechnk, class A). Ths sensor was constructed of stanless steel type and has a length of 150mm and core dameter of mm.the sensor s certfed to have a precson of 0.03K and maxmum allowable temperature of 400 o C. Ths sensor s nserted wth a depth of 46mm nsde the nternal cell body. July 11-14, 016 Purdue Conferences 1

13 3. Phase Equlbrum Apparatus/Pressure Measurement The pressure sensor used was (P390S07600,tecss), for the measurement of the absolute pressure. It has an accuracy of 0.1%, and a range of measurement between 0-16 bar. July 11-14, 016 Purdue Conferences 13

14 3. Phase Equlbrum Apparatus 1 Equlbrum Cell 3 Crculaton Pump 4 Quck (Plug)Samplng Valve 5 Samplng U-Tube 6 Heat Exchanger July 11-14, 016 Purdue Conferences 14 4

15 3. Phase Equlbrum Apparatus M 7 T 1 Equlbrum Cell 3 Crculaton Pump 1 M 4 4 Quck (Plug) Samplng Valve T p 5 5 Samplng U-Tube Heat Exchanger 8 DMA July 11-14, 016 Purdue Conferences 15

16 3. Phase Equlbrum Apparatus It was recommended to construct two addtonal quck plug valves (316 stanless steel, Swagelok) wthn the crculaton loop, to sample a mnmum amount of the flud phase n a U-tube located between these two valves. The length of the U-tube s about 170 mm and s able to hold a flud volume up to 10 ml. Source: Swagelok The plug valve was equpped wth two connectons (6mm) and desgned to wthstand a maxmum workng pressure of 06 bar. Ths quck connector body s connected wth a U-tube constructed of stanless steel and desgned to hold the requred sampled fluds. July 11-14, 016 Purdue Conferences 16

17 3. Phase Equlbrum Apparatus The upper and lower parts of the U-tube s connected wth the stem and body quck connector. Source: Swagelok The stem and the body was desgned to operate at temperature range of o C and maxmum operatng pressure of 05 bar. By ths method the problem of changng the volume n the equlbrum cell and possbly changng the homogenety of the phases was solved. July 11-14, 016 Purdue Conferences 17

18 4. Concentraton Measurement/Vbratng Tube Denstometer Densty Expermental Set up: P DMC ISOCHAM VP CT WV IN1,IN EX HP SP V4,V5 V1,V Pressure Measurement Densty Measurng Cell Isolaton Chamber Vacuum Pump Cold Trap Waste Vessel Inlet Ext Hand Pump Spndle Pump Inlet Valve Measurng Cell Valve July 11-14, 016 Purdue Conferences 18

19 4. Concentraton Measurement Measurement of the concentraton of the Mxture The U-tube s then connected wth the entrance at the Vbratng Tube Denstometer Apparatus. The requred concentratons for the mxture were detected as a functon of the densty and the perod of oscllaton. Also to verfy the concentraton of the pure fluds and mxtures a specfc algorthm wrtten n Matlab was executed, and the concentraton was further obtaned from the thermodynamc models. y V 1 P = P V, V P P 1, V 1, V ρv ρ 1, V = ρ, V ρ 1, V x L 1 P = P L, L P P 1, L 1, L = ρ ρ ρ L, L 1, L ρ 1, L July 11-14, 016 Purdue Conferences 19

20 5. Thermodynamc Modelng of Densty and Phase Equlbra G E -Models Real flud mxtures devated from dela mxture through the excess propertes. Real Lqud Phase Behavor. All the excess propertes are derved from Excess-Gbbs Energy as functon of the Temperature T,Pressure p and Thermal Equaton of State (EOS) Form of : f ( T, p, V, ) = 0 Real Vapor Phase Behavor. Example: x Vral, Cubc Equaton of State (EOS) composton x E G = f ( T, p, x ) E E S, H, V E Models: Wlson, (mod.) UNIFAC, UNIQUAC July 11-14, 016 Purdue Conferences 0

21 5. Thermodynamc Modelng of Densty and Phase Equlbra G E -Models: UNIFAC*, mod. UNIFAC** The soluton s made of molecular fragments (subgroups). New varables (R k and Q k ). Combnatoral part s the same as UNIQUAC. Source: Gmehlng *AlCheE J 1, 1086 ** Ind. Eng. Chem. Res. 6, 137 July 11-14, 016 Purdue Conferences 1

22 5. Thermodynamc Modelng of Densty and Phase Equlbra G E -Models: UNIFAC*, mod. UNIFAC** E E g = h + Ts E ln γ = lnγ + lnγ R C Resdual Part Combnatoral Part lnγ R = f ( x, q, ψ ) lnγ C = f ( x, q, r ) anm + bnmt + c Ψ = exp T a nm, b nm, c nm : nteracton parameter between Groupe m and n. q,r : geometrc molecular parameter nm T *AlCheE J 1, 1086 ** Ind. Eng. Chem. Res. 6, 137 July 11-14, 016 Purdue Conferences

23 5. Thermodynamc Modelng of Densty and Phase Equlbra Thermal Cubc Equaton of State( TCEOS) General Form: p = RT v b v a( T) + ubv + wb Parameter a and b from thermo-physcal data For mxture Mxng rule a Mx = = repulsve Part f ( a1, a,...), bmx f ( b1, b,...) Dfferent forms depend on u and w: attractve Part u=1,w=0 (Soave-Redlch-Kwong): u=,w=-1 (Peng-Robnson) RT a( T ) p = v b v( v + b) p = RT v b v a( T ) + bv b July 11-14, 016 Purdue Conferences 3

24 5. Thermodynamc Modelng of Densty and Phase Equlbra Volume Translated Peng Robnson Equaton of State (Gmehlng & Ahlers): Usually the lqud phase s not correctly descrbed by the EOS method: Here s new crtera to modfy ths error. p C p C c = v - v Exp c Maxwell Maxwell v v Introduced thrd parameter (c), known as Volume Translaton Parameter. Volume translated PR (VTPR): RTc c = Z c P c ( ) RT a( T ) p = v + c b ( v + c)( v + c + b) + b( v + c b) July 11-14, 016 Purdue Conferences 4

25 5. Thermodynamc Modelng of Densty and Phase Equlbra Combnaton of G E -Model and thermal Cubc EOS Huron-Vdal-Method van-der-waals u=w=0: Consder: Led to: E g RT Analogy for Peng-Robnson: and Soave-Redlch-Kwong: 1 a a ( v xv ) + x = v b p x + ln v b RT RT 0 0 E E v = b, g = g for p a a E = x g b b a a E + = x g ln b b a b = x a b E g ln v v 1 July 11-14, 016 Purdue Conferences 5

26 5. Thermodynamc Modelng of Densty and Phase Equlbra Combnaton of G E -Model and thermal Cubc EOS Modfed-Huron-Vdal Frst Order (MHV1) Cosder: Led to: = 0, f and f set for every EOS. Modfed-Huron-Vdal Second Order (MHV) MHV1 + EOS + mod. UNIFAC SRK-EOS + MHV delvered v a b E = x a b g f f E = + g g f E 0 E 0 + for RT f x p 0 b ln b f E g 0 b f1( α xα ) + f( α xα ) = + x ln RT b Wth: a f 1 = 0,478, f = 0,0047, α = brt MHV delvers non lnear relatons between parameter a and b. July 11-14, 016 Purdue Conferences 6

27 5. Thermodynamc Modelng of Densty and Phase Equlbra Combnaton of G E -Model and thermal Cubc EOS The theoretcal quadratc dependency of the Vral coeffcent B(T) was not consdered by the MHV two mxng rules. Wong-Sandler-Mxng rule was ntroduced: a a B( T ) = b = x x j b = Bj ( T ) RT j RT j consderng: b = j xx j b f 1 RT a RT j, f = a / b For Peng-Robnson consdered: f a b g ln(, 1) = x p E 0 0 July 11-14, 016 Purdue Conferences 7

28 5. Thermodynamc Modelng of Densty and Phase Equlbra Combnaton of G E -Model and thermal Cubc EOS VTPR + MHV1 and MHV Parameter a, b and c for pure fluds: Here Twu-Functon: Mxng rules for a, b and c; from MHV1,MHV wth UNIFAC: ) ( ) )( ( ) ( b c v b b c v c v T a b c v RT p = ),, ( ),, ( )), (,, ( c c c c c c c v p T f c p T f b T p T f a = = = α + = 0,64663, 0 R E g b a x b a )] (1 exp[ ) ( 1) ( MN r M N r T L T T = α Resdual Part ), ( ),, ( c x f c b x f b = = July 11-14, 016 Purdue Conferences 8

29 6. Results and Dscusson Mxture Attractve Energy Parameter (a) predcted for VTPR, PR EOS wth VTPR; MHV1, WS and MHV mxng rules for the system R15a (1) and R365mfc (): Co-Volume Parameter for Predctve Models wth 30% and 70% R15a: July 11-14, 016 Purdue Conferences 9

30 6. Results and Dscusson Vapor Pressure for R365mfc wth Saturaton Temperature: Relatve Devaton n Vapor Pressure Measurement Data of R365mfc: July 11-14, 016 Purdue Conferences 30

31 6. Results and Dscusson Measurement of mass fracton for the system R15a-R365mfc from vapor pressure and lqud densty data: Relatve devaton n lqud mass fracton measurement data of R15a and R365mfc July 11-14, 016 Purdue Conferences 31

32 6. Results and Dscusson Relatve devaton to expermental data of NIST (Outcalt and McLnden,1996), (McLnden and Lemmon,013) n saturated lqud densty for the system R15a and R365mfc from VTPR: Relatve devaton to expermental data of NIST (Outcalt and McLnden,1996), (McLnden and Lemmon,013) n saturated lqud densty for the system R15a and R365mfc from VTPR- MHV: July 11-14, 016 Purdue Conferences 3

33 7. Concluson and Recommendaton The sample procedure used at the crculaton loop of the VLE apparatus, has a great effect n solvng the problems of changng the volume of the fluds nsde the equlbrum cell, snce the samplng unt needs a mnmum amount of flud to be sampled. The analyss procedure used at the Vbratng Tube Denstometer apparatus could be conducted at varous condtons (p,t). The work testfy necessary applcatons of the new equaton of state VTPR, combned wth UNIFAC method as well as varous mxng rules. McLnden et.al model (NIST) acheved vapor pressure devatons of less than 0.073% for R365mfc. The concentraton devatons reached -3.1%,-9.8% for a composton of 33.6% R15a and 44.1% R365mfc respectvely. The combnaton of the G E -Model (Unfac-Modfed Unfac) wth the thermal CEOS VTPR was led to better results wth mnmum devatons from expermental data. July 11-14, 016 Purdue Conferences 33

34 7. Concluson and Recommendaton The devatons of VTPR and VTPR-MHV have led to smlar results data n the pure fluds and the mxture respectvely. The Twuαfuncton combned n the energy parameter (a) of the VTPR and VTPR- MHV models enables to wden the temperature range. The mxng rules for the energy (a) and co-volume parameters (b) ntegrated at VTPR and VTPR-MHV models allowed the predcton of the hghly asymmetrc fluds R15a. The vapor phase should also be sampled usng the same method wth specal concerns to the vacuum problem. July 11-14, 016 Purdue Conferences 34

35 Thank You DAAD Deutscher Akademscher Austausch Denst e.v German Academc Exchange Servce July 11-14, 016 Purdue Conferences 35