Joule-Thomson Refrigerator Research Articles

Study on the establishing-process of piston offset in the helium valved linear compressor under different operating parameters

The piston offset in the helium valved linear compressor (VLC) deteriorates the cooling capacity and operation life of the Joule-Thomson (JT) refrigerator, especially in aerospace applications. To clarify the influence mechanism of operating parameters on the offset characteristic of the VLC, a relative quantitative investigation is theoretically and experimentally proposed. Based on the reliable VLC developed in our lab in the hope of using for the space infrared detector, the main parameters involving the charging pressure, operating frequency, piston displacement and valve opening are systematically studied. The offset amplitude, establishment time and start-up characteristic of the offset under different conditions are presented. The equation that contains all the operating parameters capable of describing the offset values is expressed. The polynomial fitting from the experimental data verifies the deduced equation, and further explains the interaction between the offset and the operating parameters quantitatively. This study can be an effective guidance in reducing or even eliminating the offsets to improve the performance of the VLC.

Flow condensation pressure drop characteristics of zeotropic mixtures of tetrafluoromethane/ethane: Experimental and analytical investigation

Mixed-refrigerant Joule-Thomson (MRJT) refrigeration systems have distinct advantages in the temperature range from 80 to 230 K. Tetrafluoromethane (R14) and ethane (R170) are important components to improve the recuperation process in the middle and low temperature regions of a MRJT refrigeration system. In this paper, an experimental investigation on condensation pressure drop characteristics of R14/R170 mixtures (0.193/0.807, 0.437/0.563, 0.632/0.368 and 0.799/0.201 by mole) in a horizontal smooth tube was carried out. Experiments were implemented at mass fluxes from 100 to 350 kg m−2 s−1, saturation pressures from 1.5 to 2.5 MPa and heat flux from 8.4 to 44.22 kW m−2 over the entire range of vapor quality. The different contributions of frictional pressure drop and deceleration pressure drop were calculated and compared. The effects of concentration, mass flux, saturation pressure, heat flux and vapor quality were analyzed and discussed. Finally, a new flow pattern-based pressure drop correlation was developed with a good predictive ability for the present experimental data with a MARD of 8.63%, and 14.20% for the literature data. The model considers the combined effects of the individual pressure drops of liquid and vapor as well as the frictional pressure drop due to the liquid-vapor interaction.

Experimental and analytical investigation on flow condensation heat transfer of zeotropic mixtures of tetrafluoromethane/ethane

Tetrafluoromethane (R14) and ethane (R170) are important components to improve the recuperation process in the middle and low temperature regions of a mixed-refrigerant Joule-Thomson (MRJT) refrigeration system. In this paper, an experimental investigation on flow condensation heat transfer characteristics of R14/R170 mixtures (0.193/0.807, 0.437/0.563, 0.632/0.368 and 0.799/0.201 by mole) in a horizontal smooth tube was carried out. Experiments were implemented at mass fluxes from 100 to 350 kg m−2 s−1 and saturation pressures from 1.5 to 2.5 MPa over the entire range of vapor quality. The effects of concentration, mass flux, saturation pressure and vapor quality were analyzed and discussed. Compared with linear interpolation values of pure fluids, heat transfer degradation of mixtures increases with the rise of vapor quality. In addition, all experimental data were compared with sixteen well-known correlations combined with equilibrium method. It is found that all models underestimate the current experimental data. This should be due to the neglect of the intensifying effect of vapour-liquid interface fluctuation. Finally, an improved heat transfer correlation for zeotropic mixtures was proposed and predicted the experimental results well with a mean absolute relative deviation of 13.91%.

An analytical method for ensuring the optimal circulating composition of the multicomponent refrigerant mixture in a steady-state operation mode of the Joule-Thomson refrigerator operating with mixtures

Single and multi-stage Joule-Thompson refrigerators operating with natural nitrogen-hydrocarbon mixtures are marketable for creating refrigeration equipment for freezing and cryopreservation of biomedical materials, liquefaction of certain gases, high-temperature superconductors cooling, conducting climate tests without using cryogenic liquids. One of the main objectives of the development of such refrigerators is to determine the optimal weight of mixed-refrigerant charge with the known geometry of the refrigeration circuit and to ensure the optimal “circulating” composition in the steady-state mode. This article proposes an analytical method for solving this problem and presents the experimental results. The accuracy of the method is determined by the validity of calculating thermodynamic properties of the mixed refrigerants forming solutions with limited solubility in the liquid phase and by taking into account the shift of the “circulating” working body composition relative to the “charge” composition in the steady-state mode due to structural specifics of real refrigerators. The application of the method will allow reducing the time and cost of experimental development of new refrigeration equipment.

Binary mixture isothermal vapour-liquid equilibrium: Trifluoromethane (R23) + octafluoropropane (R218) at the temperature from 223.150 K to 263.150 K

The mixed-refrigerant Joule-Thomson refrigerator (MJTR) is simple in structure, safe and reliable, and is suitable for temperatures from 80 to 230 K. Trifluoromethane (R23) and octafluoropropane (R218) are satisfactory as non-flammable refrigerants in MJTR. In this paper, the gas-phase single-cycle method was used to conduct a vapor–liquid equilibrium (VLE) experiment on the R23 + R218 binary system in the temperature range from 223.150 K to 263.150 K. The VLE experimental data were correlated using the Peng-Robinson (PR) equation of state and the Huron-Vidal (HV) mixing rule combined with non-random two-liquid (NRTL) activity coefficient model. The maximum average absolute relative deviation of pressure (AARDp) and the maximum average absolute deviation of vapor phase composition (AADy) are 0.67% and 0.005, respectively.

Experimental research on a Joule-Thomson refrigeration cycle with mixture R170/R290 for −60 °C low-temperature freezer

This paper presents an experimental investigation on a Joule-Thomson cycle based low-temperature freezer for −60 ℃ refrigeration. Natural binary mixture ethane/propane (R170/R290) adopted in the freezer was proved feasible to get the low temperature below −60 ℃ refrigeration in the experimental research. The influences of the mass fraction ratio and ambient temperature on the system’s dynamic operation characteristics in the cool-down and on–off cycle processes were analyzed in detail. The results indicated that the concentration of the mixture significantly impacted system performance. The lowest freezing temperature, fastest cool-down rate, and minimum daily energy consumption of 3.612 kW h were obtained at the optimal R170 concentration of 35%. The excessively high concentration of the low boiling temperature component R170 could contribute to a drastic increase in the discharge pressure and discharge temperature, which reduced the compressor operation reliability. The compressor worked with a high compression ratio ranging from 21.8 to 26.8 in the selected operating conditions. Hence, reducing the operating pressure and compression ratio should be the possible directions to improve the low-temperature Joule-Thomson refrigerator’s performance working with R170/R290.

Performance Characteristics of a Joule–Thomson Refrigeration System with Mixed Refrigerant Composition

As the use of semiconductors in industrial site increases, research on ultra-low refrigerators is required to increase the life and quality of the semiconductors. While various types of refrigerators exist, Joule–Thomson refrigeration with the mixed refrigerant is preferred because of its compactness and stability. The performance of Joule–Thomson refrigeration with mixed refrigerants is based on the mixing ratio of the refrigerants. Therefore, in this study, three kinds of refrigerant groups, namely high boiling point (R-600a), middle boiling point (R-23), and low boiling point (R-14), are used to examine the change in the system’s performance according to the composition ratio of each refrigerant. The results indicate that as the ratio of the high boiling point refrigerant increases, the discharge, and suction temperature decrease. As the ratio of the middle boiling point refrigerant increases, the condensation pressure decreases, and thus, the inlet temperature of the expansion valve also decreases. As the ratio of the low boiling point refrigerant increases, the cooling capacity tends to increase.

Multi-evaporator Joule-Thomson cryogenic refrigeration cycles created by pumping and suction mechanisms

Due to the simple structure and low production cost of Joule-Thomson (JT) refrigeration cycles, these cryogenic systems have widely been used in many food or medicine industries. However, in many scenarios, two or even three cryogenic temperatures are needed to simultaneously supply different cryogenic cooling loads since each product has its own comfort low-temperature range. In this case, multi-evaporator JT systems can be a promising solution to address several cryogenic temperatures via employing different evaporators. Following this objective, an innovative triple-evaporator JT cycle is proposed, where the pressure difference between evaporators is created via a pumping mechanism by employing two vacuum pumps between the evaporators. In order to enhance the overall performance of this pumping-based triple-evaporator JT system, the two vacuum pumps are replaced by two ejectors and it is called the suction-based triple-evaporator JT cycle. To address the unbalanced term in energy equation of the internal heat exchanger due to the high temperature difference between the heat source and heat sink, an ejector expander JT cycle is used as a precooling cycle. Using nitrogen as working fluid, the performance of the proposed triple-evaporator JT systems is evaluated from the first and second laws of thermodynamics standpoints. Genetic algorithm method is used to optimize performance of the two proposed systems and the results are compared with each other. It is found that the optimum coefficient of performance (COP) and exergy efficiency of the suction-based triple-evaporator JT cycle are around 107% and 92% higher than those of the pumping-based triple-evaporator JT cycle, respectively. The optimum cooling load, total consumed electricity, COP, and exergy efficiency are computed 22.1 kW, 1523 kW, 0.0145, and 2.7% (for the pumping-based triple-evaporator JT cycle) and 24.94 kW, 828.2 kW, 0.0301, and 5.2% (for the suction-based triple-evaporator JT cycle), respectively.

Adiabatic Two-Phase Flow Patterns for Zeotropic Mixtures of Tetrafluoromethane/Ethane in a Horizontal Smooth Tube

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) systems have distinct advantages in the temperature range from 80 to 230 K. Tetrafluoromethane (R14) and ethane (R170) are essential components of mixed-refrigerants. Heat transfer and pressure drop for twophase flow are closely related to corresponding flow patterns. In this paper, an experimental investigation on adiabatic twophase flow patterns for R14/R170 mixtures in a horizontal smooth tube with inner diameter of 4 mm was presented. Experiments were carried out at mass fluxes from 100 to 350 kg m−2 s−1 and saturation pressures from 1.5 to 2.5 MPa over the entire range of vapor quality. The effects of concentration, mass flux, saturation pressure and vapor quality were analyzed and discussed. Furthermore, the observed flow patterns were compared with six existing flow pattern maps. Our previous model developed for pure R14 shows the best predictive ability with 80.16% of the data points can be accurately predicted.

Performance of J–T refrigerators operating with mixtures and coiled wire-finned heat exchangers

Joule–Thomson refrigerators operating with mixtures require heat exchangers with an effectiveness of over 96% for the system to function. The hot (high pressure) stream enters the heat exchanger in a superheated condition and leaves in a subcooled state. The cold (low pressure) stream, on the other hand, enters the heat exchanger in a two-phase state and leaves in a superheated state. The streams undergo a temperature change of over 200 K in the heat exchanger. The above requirements mandate the use of innovative heat transfer surfaces in the heat exchanger. Coiled wire-finned heat exchangers have been employed successfully in this work. In this paper, we present the performance of the J–T refrigerator with two different wire-finned heat exchangers (wire-fin pitches of 8 mm and 12.7 mm) measured in our test stand. About 20 K lower temperature could be obtained when the wire-fin pitch was changed from 12.7 to 8 mm. The exergy efficiency of the refrigerator also improved.

Condensation two-phase flow patterns for zeotropic mixtures of tetrafluoromethane/ethane in a horizontal smooth tube

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) systems have distinct advantages in the temperature range from 80 to 230 K. Tetrafluoromethane (R14) and ethane (R170) are essential components of mixed-refrigerants. In this paper, the adiabatic flow pattern map for R14/R170 mixtures was firstly developed based on previous flow pattern data. Then an experimental investigation on condensation two-phase flow patterns for R14/R170 mixtures (0.193/0.0.807, 0.437/0.563, 0.632/0.368 and 0.799/0.201 by mole) in a horizontal smooth tube with inner diameter of 4 mm was presented. Experiments were carried out at mass fluxes from 100 to 350 kg m−2s−1, saturation pressures from 1.5 to 2.5 MPa and heat fluxes from 8.4 to 42.2 kW m−2 over the entire range of vapor quality. The effects of mass flux, saturation pressure, heat flux and concentration on flow pattern evolutions were discussed and presented. Analysis results indicated that mass transfer resistance and heat flux account for the nonequilibrium effects of zeotropic mixture condensation, which leads to the different evolutionary trends between condensation and adiabatic two-phase flow. Finally, a new condensation flow pattern map was deduced by containing nonequilibrium effects into adiabatic flow pattern map.

Two-phase flow condensation pressure drop of R14 in a horizontal tube: Experimental investigation and correlation development

Tetrafluoromethane (R14) is an important fluid in three-stage-cascade refrigeration and mixed-refrigerant Joule-Thomson refrigeration (MJTR). In this work, an experimental investigation on condensation pressure drop of R14 in a horizontal smooth tube with inner diameter of 4 mm was carried out. Experiments were implemented at mass fluxes from 150 to 650 kg/(m2 s), saturation pressures from 1 to 3 MPa and heat fluxes from 8.3 to 28.2 kW/m2 over the entire range of vapor quality. The effects of heat flux, mass flux, saturation pressure and vapor quality were analyzed and discussed. In addition, the frictional pressure drops were compared with twenty-nine well known frictional pressure drop correlations. An improved frictional pressure drop correlation was deduced and predicted R14 experimental data well with a mean absolute relative deviation of 12.18%. Finally, 2317 data points from nineteen published literature were adopted to evaluate the predictive ability of this new model. It achieves a satisfactory predicting result with a mean absolute relative deviation of 17.39% and 87.26% of the experimental data within the deviation bandwidth of ±30%.

Experimental investigation on the concentration distribution behaviors of mixture in an ejector enhanced auto-cascade refrigeration system

In this paper, the concentration distribution behaviors of the mixture R134a/R23 in an ejector enhanced auto-cascade refrigeration cycle (EARC) were experimentally investigated. Relationships between circulating concentration and charged concentration were explored, and the effects of the heat load and ambient temperature on the composition shift characteristics were analyzed. The results indicated that large composition shift occurred at the operation conditions, and the circulating concentration of the low boiling temperature component R23 at the condenser inlet was 25.9–38.1% higher than that in charge due to the differential hold-up of individual refrigerant components in two-phase region. The concentrations of the component in charge and circulation had a linear relationship in EARC, which was similar to those in conventional auto-cascade refrigeration cycle and Joule–Thomson refrigerator, even though these cycles were different in cycle configurations, mixture and operation conditions. R23 showed higher circulation concentration at higher ambient temperature. As the increasing heat load, the circulating concentration of R23 at the condenser inlet first increased and then decreased. In addition, different preferential solubility of individual components in the lubricating oil led to 15.4% richer R23 before the system start-up than that charged. The circulating concentration varied drastically at the early stage of the pull-down process and then tended to be stable over time. The largest shift of the circulation concentration from the charged concentration in the pull-down process reached 32.6%. This work could provide an in-depth understanding of the behaviors of the mixture concentration in the ejector enhanced auto-cascade refrigeration system.

Boiling Heat Transfer Characteristics for Methane, Ethane and Their Binary Mixtures

Methane (R50) and ethane (R170) are the dominated components of natural gas and the important components in mixture refrigerants for the mixture Joule–Thomson refrigeration cycle. In this article, experimental investigations on nucleate pool boiling and flow boiling heat transfer characteristics of R50, R170, and their binary mixtures are presented. The effects of saturation pressure, heat flux, mass flux, concentration, and vapor quality on heat transfer coefficients are analyzed and discussed. Firstly, the pool boiling heat transfer data were compared with six well-known correlations. Labuntsov correlation shows the best agreement with a mean absolute relative deviation (MARD) of 11.3%. Secondly, a new flow boiling heat transfer correlation for pure fluids was proposed based on the asymptotic addition of forced convection and pool boiling. The modified enhancement factor and suppression factor were developed to account for their relative contribution. In addition, in order to consider the mass transfer resistance of mixtures, a new mixture factor was deduced. The new flow boiling heat transfer correlations can well predict the experimental data with the MARD of 9.5% for pure fluids and 8.3% for mixtures.

Experimental investigation of cycle characteristics of a R23 and R600a based Joule-Thomson refrigerator

This paper proposes a novel refrigerant pair, i.e., R23(trifluoromethane) and R600a(isobutane), for Joule-Thompson (JT) refrigerating systems for 200 K applications, and investigates its performance in a modified smaller domestic cooler. The influence of the refrigerant ratios and the condensing temperature on the JT performance is investigated, and optimized parameters are proposed for further prototypes. It is suggested that R23/R600a is a good refrigerant pair for the JT system, and a compositional ratio of 3:7 is suitable for the designed application. The dynamic response of the refrigerating system shows that the proposed refrigerant pair can reach stable operating conditions within 45 min and the variation of the condensing temperature has little influence on the evaporating temperature, partly due to the full condensation of the refrigerant pair before the throttle process.

Investigation of the ejector application in the cryogenic Joule-Thomson refrigeration system

We investigate the application of ejector in the cryogenic refrigeration system. A new refrigeration cycle is proposed using ejector technology to enhance the thermodynamic efficiency of Joule-Thomson (JT) refrigeration system. The ejector combined with the JT refrigeration cycle works with nitrogen and neon mixed refrigerant. The target refrigeration temperature is aimed to near the freezing point of nitrogen (63.15 K). A performance map of ejector-JT cycle is accomplished according to the ejector entrainment ratio and the ejector exit pressure. The effect of the ejector on the refrigeration cycle COP is analyzed by calculating the exergy destruction rate at each component of the refrigeration cycle. The exergy analysis shows that the losses at every component of the refrigeration cycle can be reduced using ejector when the entrainment ratio is properly designed. A lab-scale prototype ejector which has a rectangular cross sectional area is fabricated by stacking thin layers of etching plates. The fabricated lab-scale ejector is tested with JT refrigeration circuit, and the nozzles and the diffuser showed 80% isentropic efficiency.

Design of high-efficiency Joule-Thomson cycles for high-temperature superconductor power cable cooling

Liquid nitrogen (LN2) is commonly used as the coolant of a high temperature superconductor (HTS) power cable. The LN2 is continuously cooled by a subcooler to maintain an appropriate operating temperature of the cable. This paper proposes two Joule-Thomson (JT) refrigeration cycles for subcooling the LN2 coolant by using nitrogen itself as the working fluid. Additionally, an innovative HTS cooling cycle, of which the cable coolant and the refrigerant are unified and supplied from the same source, is suggested and analyzed in detail. Among these cycles, the highest COP is obtained in the JT cycle with a vacuum pump (Cycle A) which is 0.115 at 78 K, and the Carnot efficiency is 32.8%. The integrated HTS cooling cycle (Cycle C) can reach the maximum COP of 0.087, and the Carnot efficiency of 24.8%. Although Cycle C has a relatively low cycle efficiency when compared to that of the separated refrigeration cycle, it can be a good alternative in engineering applications, because the assembled hardware has few machinery components in a more compact configuration than the other cycles.

Estimation of performance of a J-T refrigerators operating with nitrogen-hydrocarbon mixtures and a coiled tubes-in-tube heat exchanger

The exergy efficiency of Joule-Thomson (J-T) refrigerators operating with mixtures (MRC systems) strongly depends on the choice of refrigerant mixture and the performance of the heat exchanger used. Helically coiled, multiple tubes-in-tube heat exchangers with an effectiveness of over 96% are widely used in these types of systems. All the current studies focus only on the different heat transfer correlations and the uncertainty in predicting performance of the heat exchanger alone. The main focus of this work is to estimate the uncertainty in cooling capacity when the homogenous model is used by comparing the theoretical and experimental studies. The comparisons have been extended to some two-phase models present in the literature as well.Experiments have been carried out on a J-T refrigerator at a fixed heat load of 10 W with different nitrogen-hydrocarbon mixtures in the evaporator temperature range of 100–120 K. Different heat transfer models have been used to predict the temperature profiles as well as the cooling capacity of the refrigerator. The results show that the homogenous two-phase flow model is probably the most suitable model for rating the cooling capacity of a J-T refrigerator operating with nitrogen-hydrocarbon mixtures.

Design of distributed JT (Joule-Thomson) effect heat exchanger for superfluid 2 K cooling device

Superfluid at 2 K or below is readily obtained from liquid helium at 4.2 K by reducing its vapour pressure. For better cooling performance, however, the cold energy of vaporized helium at 2 K chamber can be effectively utilized in a recuperator which is specially designed in this paper for accomplishing so-called the distributed Joule-Thomson (JT) expansion effect. This paper describes the design methodology of distributed JT effect heat exchanger for 2 K JT cooling device. The newly developed heat exchanger allows continuous significant pressure drop at high-pressure part of the recuperative heat exchanger by using a capillary tube. Being different from conventional recuperative heat exchangers, the efficient JT effect HX must consider the pressure drop effect as well as the heat transfer characteristic. The heat exchanger for the distributed JT effect actively utilizes continuous pressure loss at the hot stream of the heat exchanger by using an OD of 0.64 mm and an ID of 0.4 mm capillary tube. The analysis is performed by dividing the heat exchanger into the multiple sub-units of the heat exchange part and JT valve. For more accurate estimation of the pressure drop of spirally wound capillary tube, preliminary experiments are carried out to investigate the friction factor at high Reynolds number. By using the developed pressure drop correlation and the heat transfer correlation, the specification of the heat exchanger with distributed JT effect for 2 K JT refrigerator is determined.

An Identification of the Best Mixture Composition for the Joule-Thomson Refrigerator Operating at 90 K

An Identification of the Best Mixture Composition for the Joule-Thomson Refrigerator Operating at 90 K