Research progress on cryogenic mixed-gases Joule-Thomson refrigeration in TIPC of CAS Maoqiong GONG Technical Institute of Physics and Chemistry (TIPC) Chinese Academy of Sciences (CAS) Email: gongmq@mail.ipc.ac.cn Tel/Fax: 86-1-82543728
Contents 1. Introduction 2. Thermophysical properties and components selection of mixed-refrigerants 3. Thermodynamic features of the recuperative heat exchangers 4. Thermodynamic optimization of various cycle configurations 5. Composition shift 6. Performance and application of cryogenic MJTR
1. Introduction
Refrigeration requirements in different temperature ranges 37 Near ambient temperature range 23 Domestic refrigerators Air conditioners Heat pumps etc. Deep cooling temperature range biomaterials Medicine Energy Aerospace 8 The mixed-gases Joule-Thomson refrigerator (MJTR) can satisfy such requirements The MJTR play the dominant role in this deep cooling temperatures ranging from 8 to 23 K
The mixed-gases Joule Thomson refrigerator 37 Near ambient temperature range 23 Deep cooling temperature range Advantages of MJTR Off-the-shelf components High reliability. Low cost. Easy to be built in large scale. 8
The mixed-gases Joule Thomson refrigeration 37 Near ambient temperature range 23 Deep cooling temperature range 8 Technical challenges & Scientific problems Mixture Components selection and optimal composition. Cycle configurations with high efficiency and reliability. Mixtures properties in large temperature span. Working mechanism of lowtemperature mixed-gases Joule- Thomson refrigeration. Accurate component design and manufacture
2. Thermophysical properties and components selection of mixed-refrigerants
T/K 2.1 Phase equilibria Fluid equilibrium is the fundamental for other thermal physical properties. Basic parameters for other properties prediction Determining the lowest evaporation temperature of the MJTR Experiments is most important and final method for phase equilibria study Several facilities were built to study the mixtures VL(L)E behaviors used MJTRs 19 18 17 liquid-correlated vapor-correlated liquid-predicted vapor-predicted 16 Influence of the presence of experimental data on the prediction results 15.1 MPa 14..1.2.3.4.5.6.7.8.9 1. x 1, y 1 R14+R17 system
2.1 Phase equilibria First apparatus for low-temperature cryogenic apparatus T: 8~3 K p:.1~1 MPa Temperature uncertainty : ±1mK Pressure uncertainty: ±2kPa Composition uncertainty : ±.3
2.1 Phase equilibria (CH 4 +CF 4 +C 2 H 6 system) CF 4 CH 4 +CF 4 system.2. 1..8 C 2 H 6 +CF 4 system VLE of ternary system.6.4.6.4.8 L+V.1 MPa.2 C 2 H 6 1....2.4.6.8 1. CH 4
2.1 Phase equilibria (R17+R23+R116 system) R17+R23 system(212.84 K) R17+R116 system(252.8 K).6.4.2 R116. 1..8.6 Bubble point Dew point.4 R17+R23+R116 Ternary system.6.4.2 R116. 1..8.6 Bubble point Dew point.4.8 L+V.2 1.. R17..2.4.6.8 1. R23.8 L+V.2 L+V 1.. R17..2.4.6.8 1. R23
2.1 Phase equilibria Second apparatus for VLLE The second VLLE apparatus T: 2~31 K p:.1~5 MPa Temperature uncertainty : ±4mK Pressure uncertainty : ±.2~.5kPa Composition uncertainty : ±.2 Journal Cover Journal of Chemical & Engineering Data, 212, 57:541-544
2.1 Phase equilibria Vapor-liquid-liquid equilibria of R134+R6a system Clear single liquid phase Critical opalescence Phase separation Clear two liquid phases.9 (VLLE).85 p/mpa.8.75.7.2.3.4.5.6.7 x 1.8.9 235 236237 241 242 238 23924 T/K Experimental data of the vapour-liquid-liquid equilibria of {R134+R6a} system
Comparison of vapor liquid equilibria experimental facilities Institutes Experiment method Temperture uncertainty /mk Pressure uncertainty /kpa Seoul National University Vapor cycle 2 1.3 Ecole Nationale Supérieure des Mines de Paris CENERG/TEP, France Korea Institute of Science and Technology (KIST), South Korea Static method 1.3.2 Vapor and liquid double cycle 1 1.2 Institute of Building Technologies, Italy Vapor cycle 2 1.3 Ajou University, Korea Vapor cycle 2 2.3 Instituto Politecnico Nacional, Mexico Static method 3.4%.1 National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, Japan TIPC,CAS Three facilities, temperature: 8~4 K pressure:.1-1 MPa Vapor and liquid double cycle Vapor cycle quasi-static Vapor cycle 3.62.1 4 4 1.3.26 2 Mole Composition uncertainty.3.2.2
p/mpa 2.1 Phase equilibria Azeotropy prediction model of the equilibria pressure extremum. dp ( y x ) (d d ) d x ( v v ) dx 1 1 1 2 V L 1 1 2 d p dx 2 1 2 d p dx 2 1 Positive azeotropic Negative azeotropic (Theoretical prediction model).6.5.4.3.2..2.4.6.8 1. x 1,y 1 Combined with experimental data, mixing principles for PR thermodynamic model equations was improved, binary interaction coefficients were also obtained. Predictions of the binary azeotropic characteristics of several systems were conducted.
Summary on vapor-liquid equilibria work Some VLE data of mixtures was were first measured: HCs + R14/R23/R116 and other systems; Some of the theoretical predictions and correlation models were established and improved; There are still many problems: 1) Gas-liquid, liquid-solid equilibria of oil with refrigerants 2) Vapor-liquid-liquid equilibria; 3) High-precision theoretical prediction model.
T /K 2.2 Throttling effect Some conceptions Throttling device 7 6 K T s T r 5 4 JT > JT < High pressure, high temperature gas Low pressure, low temperature gas 3 2 1 L 1 2 3 4 5 6 p /MPa P N N Basic conceptions of throttling effects
Isotherm al throttle effect (kj/m ol) 2.2 Throttling effect 25 2 15 1 5 N2 Pl=.1MPa CH4 C2H6 1 2 3 4 5 C3H8 ic4h1 ic5h12-5 5 1 15 2 25 3 35 Temperature (K) The higher pressure before throttling, the wider temperature range would be covered with effective throttling effect. 1. P H =1.MPa, 2. P H =2.MPa, 3. P H =3.MPa, 4. P H =4.MPa, 5. P H =5.MPa Influence of pressures and temperatures on pure substance throttling effects
isothermal JT effect(j/mol) integrated JT effect (K) 2.2 Throttling effect 7, 6, 5, 4, 3, 2, 1, 2 1.5 P(MPa) 1.5 1 15 25 2 T(K) 7, 6, 5, 4, 3, 2, 1, 7 6 5 4 3 2 1 2 1.5 P(MPa) 1.5 1 15 25 2 T(K) 7 6 5 4 3 2 1 14, 5 8 5 12, 1, 8, 6, 4, mix.1 mix.2 mix.3 Isothermal J-T effect 7 6 5 4 3 2 mix.1 mix.2 mix.3 2, 1-2, 5 1 15 2 25 3 T(K) -1 5 1 15 2 25 3 T(K) Throttling effect of mixed refrigerants under various pressures and temperatures A method for optimizing mixture composition
h T (kj/mol) 2.2 Throttling effect 25 2 p H =2. MPa p L =.1 MPa A) C 3 H 8 ic 5 H 12 ic 4 H 1 1 9 8 7 p H =2. MPa p L =.1 MPa B) C 2 H 6 C 3 H 8 ic 4 H 1 15 1 mixture CH 4 CF 4 C 2 H 6 T h (K) 6 5 4 3 mixture N 2 CH 4 CF 4 ic 5 H 12 5 N 2 2 1 9 12 15 18 21 24 27 3 T (K) 9 12 15 18 21 24 27 3 33 36 T (K) The minimum isothermal throttling effect of the optimized mixture in the whole temperature range is larger than that of any pure component, which is the reason that mixed refrigerants could increase the thermal efficiency of the MJTR cycle.
2.3 Components selection Selecting component to make their effective throttle effect temperature range cover each other (relaying) in temperatures ranging from ambient to the target. Physical and chemical stability, impact on the environment (ODP, GWP), as well as economic factor, etc. Components selection for liquid nitrogen temperature refrigeration No. Components Boiling points(k) Temperature zone 1 He, Ne 4.2, 27. Low temperature zone 2 N 2, Ar 77.4, 87.3 Normal temperature zone 3 CH 4 111.7 Low-medium temperature zone 4 CF 4 145.2 Low-medium temperature zone 5 C 2 H 4, C 2 H 6 169.4, 184.6 Medium temperature zone 6 C 3 H 8, C 3 H 6, ic 4 H 1 231.4, 225.53, 261.4 Medium-high temperature zone 7 ic 5 H 12 3.98 High temperature zone
3. Behaviors of the recuperative heat exchangers and two-phase heat transfer study
3.1 Experimental research on the operation features of tube-in-tube recuperative heat exchanger Recuperative heat exchanger is the biggest difference between mixed-gases J-T refrigeration cycle and the vapor compression cycle in terms of hardware. After cooler Recuperator Evaporator Vapor Compression Recuperative heat exchanger is a critical component of mixed-refrigerant J-T refrigerator.
HTC (W/m 2 K) / HEAT(W) ALMTD (K) HTC (W/m 2 K) / HEAT (W) ALMTD (K) T (K) 3.1 Experimental research on the operation features of tube-in-tube recuperative heat exchanger 3 275 25 225 2 175 B) A) T L _A T H _A T L _B T H _B Built a special HX with 1 sections to measure: temperature and pressure distribution Overall heat transfer coefficients 15 1 2 3 4 5 l x (m) 12 9 6 3 15 12 9 6 3 A) ALMTD HTC HEAT 1 2 3 4 5 6 7 8 9 1 n B) ALMTD HTC HEAT 14 12 1 8 6 4 2 2 15 1 5 1 2 3 4 5 6 7 8 9 1 n
3.1 Experimental research on the operation features of tube-in-tube recuperative heat exchanger T (K) T (K) HTC (W/m 2 K) / Q (W) HTC (W/m 2 K) / Q (W) ALMTD (K) ALMTD (K) 3 3 16. 25 p H p L 24 ALMTD HTC Q 12.8 2 18 9.6 15 12 6.4 1 A 3 6 A 3 3.2 5 3 25 2 15 1 1 2 3 4 5 l x (m) p H p L A 4 1 2 3 4 5 l x (m). 1 2 3 4 5 6 7 8 9 1 n 7 18 56 42 28 A 4 14 ALMTD 3 HTC Q 1 2 3 4 5 6 7 8 9 1 n 15 12 9 6 The mixture composition determines: The locations of pinch points. The distribution of heat load versus the temperature.
3.2 Researches on two-phase heat transfer of mixed-refrigerants Complicated heat and mass transfer process in the recuperator. Flow-boiling Flow-condensation
3.2 Researches on two-phase heat transfer Pool-boiling Refrigerant tank DC regulator GC Keithley 27 Computer Compressor DC regulator 2 3 1 Vacuum pump Cold light scale 5 4 High speed camera Calculated results (kwm -2 K -1 ) 1 8 6 4 2 Palen&Small [22] Jungnickel et. al [23] Thomes&Shakir [24] Fujita&Tsutsui [25] Inoue et. al [26] +25% -25% 2 4 6 8 1 Measured data(kw m -2 K -1 ) Pool-boiling experiments. Covering 8~3 K. Components of natural gas, pure substances and mixtures.
3.2 Researches on two-phase heat transfer Flow-boiling Vacume pump Vacume chamber Charging port Throttling valve Δp p Cooling loop Liquid reservoir Throttling valve Heat exchanger DC Regulator 2 DC Regulator 1 Adiabatic pressure drop test section SENSORS C:coriolis mass flow meter T: resistances thermometer p: absolute pressure sensor Δp: differential pressure sensor Heat transfer test section Maganetic gear pump C T Preheater Sight glass p T T T T Δp Sight glass Researches on two-phase flow boiling heat transfer and flow characteristics. Covering 1~3 K. Components of natural gas, pure substances and mixtures.
3.2 Researches on two-phase heat transfer Flow-boiling New correlation of flow boiling heat transfer coefficients: k htp 3 Re ( BoK).92.45Co D.875.714 L.2 In the literature (Cryogenics 57,213,18-25) on LNG heat transfer, our correlation was proven the best one with the smallest deviation. Predicted h (kw.m -2.K -1 ) 12 9 6 3 R29 R152a R17 +2% -2% 3 6 9 12 Experimental h (kw.m -2.K -1 ) the best correlation
h (W (m 2 K) -1 ) 3.2 Researches on two-phase heat transfer Flow-condensation Vacume pump Vacume chamber Cooling loop 2 DC Regulator Heat transfer test section T T T T Cooling loop 1 Magneticdriven pump Heat exchanger C T Preheater Sight glass Sight glass T T T T p Δp p Δp p Throttling valve Reservoir Adiabatic pressure drop section SENSORS C:Coriolis mass flow meter T: resistances thermometer p: absolute pressure sensor Δp: differential pressure sensor Flow condensation heat transfer and flow characteristics. Covering 1~3 K. Components of natural gas, pure substances and mixtures. G kg m -2 s -1 8 p=1.1 MPa G=22 kg (m 2 s) -1 q avg =64.4 kw m -2 7 6 5 4 3 2 1 35 3 25 2 15 1 p=1.56 MPa G=21 kg (m 2 s) -1 q avg =76.4 kw m -2 p=2.6 MPa G=21 kg (m 2 s) -1 q avg =81.9 kw m -2 p=2.56 MPa G=21 kg (m 2 s) -1 q avg =85.1 kw m -2..2.4.6.8 1. Plug Slug 5..2.4.6.8 1. x x R17 Transition Annular
4. Thermodynamic optimization of various cycle configurations
4.1 Thermodynamic optimization: single-stage cycle Optimization objective function: Maximize thermodynamic efficiency Optimization parameters: Mixture components Mixture composition High and low pressures of cycle The single-stage mixed-gases Joule-Thomson cycle
T (K) T (K) T (K) 4.1 Thermodynamic optimization: single-stage cycle (1) Compression, throttling and evaporation processes Higher high-boiling component fraction leads to a smaller compressibility factor and a lower compressor inlet temperature, reducing the compression power consumption. Lower temperature before throttling results in smaller exergy loss (2)Recuperative process When the fraction of one component gets larger, the intrinsic temperature difference in the relevant temperature zone would increase, as well as the exergy loss. 3 3 3 25 25 25 2 2 2 15 P L P H 15 P L P H 15 P L P H 1 5 1 15 2 Q HX (kj/mol) More low-boiling and middleboiling components 1 5 1 15 2 Q HX (kj/mol) More high-boiling components 1 5 1 15 2 Q HX (kj/mol) Optimized Composition
T (K) T (K) 4.1 Thermodynamic optimization: single-stage cycle 3 25 ic4 3 25 ic5 2 2 P L 15 P L P H 15 P H 1 5 1 15 2 Q HX (kj/mol) 1 3 6 9 12 15 18 Q HX (kj/mol) Optimization results: The single-stage mixed-gases J-T cycle could achieve a theoretical cycle efficiency of 63% (relative Carnot efficient).
4.2 The influence of cycle configuration Various configurations of mixed refrigerant J-T cycle
4.2 The influence of cycle configuration No phase separator Relative Carnot efficiency of 63% 63% 1% 9.5% 8.5% 9% DEAC DEHX DEJT DEEV CEF One phase separator Relative Carnot efficiency of 62.5% DEAC DEHX2 DEJT1 DBLEND DEHX3 DEJT2 DEEV CEF Two phase separators Relative Carnot efficiency of 61.5% DEAC DEJT1 DEJT2 DEHX1 DEHX2 DEHX3 DBLEND DBLEND DEJT3 DEEV CEF
Conclusions of thermodynamic analysis Different cycle configurations could reach close performances under each optimal conditions, while the single-stage cycle with the most simple structure could achieve the best performance in the thermodynamic point of view. Cycle configuration is the external factor while mixture is internal factor. Effective refrigeration could be achieved by matching the external and internal factors.
5. Composition shift
R j, % R, % 5.1 Composition shift characteristics of mixed refrigerants Circulation concentration changes from the original charged data in MJTRs Two factors: liquid holdup and solution with oil 25 2 15 1 5 N 2 CH 4 C 2 H 6 C 3 H 8 ic 4 H 1 ic 5 H 12 R T=3 K p=11.3 kpa 1 75 5 25-5 -1 1 2 3 4 5 6 7 8 9 1 R oil, % Composition shift characteristics of mixtures.
R /% R /% T /K 5.2 Composition shift caused by liquid holdup 3 25 2 15 N2 CH4 C2H6 C3H8 ic4h1 3 27 24 1 5-5 21 18 15-1 1 2 3 4 5 6 7 8 Sampling Point 12 5 4 3 2 1-1 -2-3 -4-5 -6-7 N2 CH4 C2H6 C3H8 ic4h1 14 16 18 2 22 T /K Oil-free compressor liquid holdup
5.3 Composition shift caused by solubility in lubricants Gas-liquid phase equilibria Solubility: x 1 n 1 n1 n 2 n 1 v v 1 V V bottle bottle v v v T, P v T, P v T, P v T, P beg beg 1 end end v 1 v v1 1 abs, gas T, P V pump pump V 2, cell 1 V cell Composition shift caused by the solubility in lubricants.
5.4 Composition shift characteristics Problems caused by composition shift Decreasing the concentration of high-boiling components Reduce cycle performance. Measures to reduce or eliminate the influences 1) The deep oil separation in compressor unit 2) Increasing volume ratio for warm to cold sections 3) Increasing charging quantity
6. Performance and application of cryogenic MJTR
6.1 Series cryo-freezers Cryo-freezers for biomaterial long-term preservation Six temperature zone series: -86-15 -132-154 -164-186 Ambient temperature -4-8 -12-15 -196 (LN2)
6.1 Series cryo-freezers Industrial production for almost 15 years!
6.1 Series cryo-freezers Performance comparison -86 cryogenic preservation chambers Institutes Refrigeration cycle Compressor Refrigerant Chamber volume/l Compressor displacement/cc Japan SANYO two-stage cascade lower back pressure compressor R47/ R58B+R29 US FORMA REVCO two-stage cascade lower back pressure compressor R44a / R58B+R29 This Project Mixed-gases recuperative cycle Single-stage oil-lubricated hermetic compressor Multivariate mixed refrigerant 32 328 328 47.1 (2.7+26.4) 51.2 (25.6+25.6) 34.8 25% smaller compressor displacement 16% smaller installed power (lower cost) Reducing energy consumption by ~36%. Reducing cooling time by ~3% Ultimate temperature lower more than 6K Rated input power/kw -8 energy consumption /kwh/day/l Ultimate temperature/ 1.36 1.47 1.15.84.86.54-85 -86-92 Cooling time/hr > 5 > 5 <3.5
6.2 Trailer-mounted natural gas / coalbed gas liquefier Requirements Recovery of remote and scatted natural gas resources, not suitable for pipeline and fixed LNG plant Measures: 1) Efficient and compact cold box structure. 2) Compact air-cooled compressor unit. 3) Manufacture mini-liquefiers with high flexibility. Results and effects: 5 ~1,Nm 3 /d moveable trailer-mounted liquefiers were developed. The factory-assembled production mode of the liquefiers greatly reduced the construction period
6.3 Trailer-mounted natural gas / coalbed gas liquefier The comparison of liquefaction performance with other devices No. Capacity/Feed Institutions Liquefaction technology gas pressure Gas Mixed-refrigerant Technology liquefaction process, 2 Nm 1 3 /d Institute skid-mounted,.1~.7mpa (GTI), US water-cooled 2 3 4 Harbin Cryo, Jilin Songyuan Hamworthy, UK SINTEF, Norway 5 TIPC, CAS Mixed-refrigerant liquefaction process (centralized), water-cooled Nitrogen expander process (peak load regulating) Mixed-refrigerant liquefaction process, seawater-cooled Mixed-refrigerant liquefaction process, trailer-mounted, full air-cooled 7 Nm 3 /d.3mpa 1 Nm 3 /d N/A 3 Nm 3 /d 1.82 MPa 1 Nm 3 /d.7~1.3mpa Efficiency 25% consumed, 75% liquefied 14.3% consumed, 85.7% liquefied, Calculated by the shaft power of all devices 16% consumed, 84% liquefied 16.7% consumed, 83.3% liquefied Estimated on literatures 15.3% consumed, 84.7% liquefied, Measured power consumption of all devices
Summary of the researches on cryogenic mixed-gases Joule-Thomson refrigeration in TIPC Cryo-freezers High and low temperature experiment chamber Tree crown and fruit Natural gas liquefiers Trunk Cycle configuration Mixture Composition Thermophysical properties Root Heat transfer Control and integrate technology Two-phase flow
Thank you Maoqiong Gong, Prof. Dr. Technical Institute of Physics and Chemistry Chinese Academy of Sciences Email: gongmq@mail.ipc.ac.cn