Sangkwon Jeong

• Korea Advanced Institute of Science and Technology

The cell of the sorption compressor developed in this paper has a thin-plate shape to accelerate the pressure swing by reducing the heating and cooling periods. Its width, height and thickness are 100 mm, 100 mm and 4.6 mm, respectively. Two identical cells filled with 22.8 g of charcoal mass are operated alternately to generate and maintain signif...

A conduction-cooled high temperature superconducting (HTS) solenoid is fabricated to produce pulsating 4 T magnetic field for magnetic refrigeration. HTS conductor of 245 m is wound as a solenoid with 112 layers each of which consists of 12 turns of the conductor. For a stable ramping operation of the magnet, AC loss inside the winding pack should...

A parametric study of a TESU (thermal energy storage unit), an essential component of a LAES (liquid air energy storage) system that stores a large amount of useful energy in an eco-friendly manner, is performed. The geometric conditions of the TESU cover the overall heat conductance, the volume, and the type of thermal energy storage material. The...

The integrated refrigerator composed of sorption cooler and adiabatic demagnetization refrigerator (ADR) is proposed for sub-kelvin cooling without vibration. In this configuration, the demagnetization process of the ADR is supposed to start after the termination of the sorption cooling. The liquid helium-4 inside the thermosiphon of the sorption c...

The nitrogen-charged cryogenic loop heat pipe (CLHP) was utilized as an effective cryogenic heat switch operating at around 100 K by thermally connecting or blocking a cryogenic heat source and a cryogenic heat sink. The switching-off function of the CLHP heat switch was achieved by eliminating heat load on the secondary evaporator without any dedi...

A numerical model is established to calculate the temperature and pressure distribution of the 3 km long high temperature superconducting (HTS) power cable. The model assumes that the configuration of HTS power cable is three phase co-axial shape with counter-flow cooling method. In the numerical model, the circulating nitrogen enters the inner cha...

To examine the benefit of the pressure drop effect in a heat exchanger, we designed and tested the heat exchanger with significant pressure loss in the temperature range between 4.2 K and 1.8 K. The numerical investigation was also carried out to elucidate the effect of continuous pressure drop, namely the distributed JT effect, in the heat exchang...

A sorption J-T (Joule-Thomson) refrigerator is a J-T refrigerator using a sorption compressor that compresses refrigerant by adsorption and desorption in sorption cells. When the sorption cell of the compressor is cooled, the refrigerant is adsorbed on the adsorbent, reducing the pressure of the cell. In contrast, when the cell is heated, its press...

This paper focuses on the transient process of the pipe cooling by the internal flow of cryogenic fluid, which is a so-called cryogenic line chill-down process. Due to the increasing use of cryogenic fluid in various industries, the heat transfer characteristics during the line chill-down process are followed with great interest. One of the biggest...

A conduction-cooled HTS magnet was tested to produce an AC magnetic field up to 4 T for an adiabatic demagnetization refrigerator (ADR). Quench detection was conducted by measuring the voltages in the conductor, and the protection system was constructed with an external dump resistor. The magnet, which is equipped with extensive copper thermal drai...

A cryogenic Joule–Thomson (JT) refrigerator has several advantages for large industrial applications, in the aspect of easy cooling power adjustability and high reliability due to no moving parts at low temperature. A mixed refrigerant Joule–Thomson (MRJT) refrigerator technology, which has usually exhibited good performance at refrigeration temper...

A cryogenic loop heat pipe (CLHP) provides a highly efficient thermal-conductive link between a cryogenic heat source such as an infrared detector and a cryogenic heat sink like a cryocooler in a spacecraft. The CLHP inherently has a large thermal inertia by the influence of latent heat during phase changes and large heat-transfer coefficients in b...

To examine the applicability of no-vent filling (NVF) as an LNG charging method, we carried out numerous cryogenic experiments with tetrafluoromethane (CF4) and octafluoropropane (C3F8). A numerical calculation was also conducted by the prediction model established in the previous research. As a result, the average bottom temperature was predicted...

A Stirling-type pulse tube cryocooler (PTC) with a superconducting linear motor for the compressor unit was developed and tested. The compressor was able to produce oscillating mass flow and pulsating pressure at low temperature environment near 80 K and transmitted compression work efficiently to the cold-end of the pulse tube cryocooler. Although...

The simplest cooling method to achieve 2 K is to use a subatmospheric cooling system of liquid helium, which may have high efficiency benefited from a counterflow heat exchanger. This paper describes the design and fabrication a specific heat exchanger with significant pressure drop using a capillary tube. It is called a "distributed JT (Joule-Thom...

Cryogenic fluids, such as liquid oxygen (LOX) and liquid hydrogen are used as the propellants of space vehicles. Before initiating the normal operation state, all elements in the cryogenic system need to be chilled down by consumption of the incoming the cryogenic liquid. As a result, the heat transfer characteristics during the chill-down process...

This paper describes the prospective issue of actively incorporating a cryocooler for thermal anchoring purpose to block the heat ingress from room temperature and reduce the everlasting parasitic heat load. Two systems, one with a single two-stage cryocooler and the other with two independent cascade cryocoolers, are examined in this paper to eluc...

The cryogenic line chill-down process is an essential part of the cryogenic system application. As the heat transfer characteristics during the transient cooling down are highly affected by the fluid properties, universal heat transfer correlations, which are valid for the chill-down process with various kinds of cryogenic fluid, are required in ma...

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 refrigerat...

The flow boiling heat transfer of R123/R134a non-azeotropic mixture has been experimentally studied in a single microchannel of 190 μm ID for various experimental conditions: mixture composition (R123 ratio: 0.250, 0.502, 0.746), mass velocity (G = 314–470 kg/m² s), heat flux (q″ = 10–20 kW/m²) and vapor quality (x = 0.2–0.9). The wall temperature...

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 work...

Heat transfer coefficient of a mini-channel printed circuit heat exchanger (PCHE) with counter-flow configuration is investigated. The PCHE used in the experiments is two layered (10 channels per layer) and has the hydraulic diameter of 1.83 mm. Experiments are conducted under various cryogenic heat transfer conditions: single-phase, boiling and co...

Thermodynamic vent system (TVS) is an attractive technology to maintain an allowable pressure level of a cryogenic propellant storage in a spacecraft under micro-gravity condition. There are two types of TVS; active or passive. In this paper, the passive TVS which does not utilize a cryogenic liquid circulation pump is experimentally investigated w...

The experimental investigation of an active magnetic regenerative refrigerator (AMRR) operating between 77 K and 20 K is discussed in this paper, with detailed energy transfer analysis. A multi-layered active magnetic regenerator (AMR) is used, which consists of four different rare earth intermetallic compounds in the form of irregular powder. Nume...

This paper describes a numerical 1-D model for no-vent fill (NVF) process of cryogenic fluid. It is an empirical model which has been developed by observing experimental data. Two different receiver tanks are used in the experiment to examine the geometrical influence of the model. The filling process is mainly divided into an initial flash evapora...

The lowest attainable refrigeration temperature of a nitrogen based Joule–Thomson refrigerator is generally limited to 77 K since the compressor suction pressure is usually higher than atmospheric pressure. The Joule–Thomson process with an ejector is proposed to achieve a refrigeration temperature as low as 68 K by adjusting the evaporation pressu...

In a free-piston expander which eliminates mechanical linkages, a prescribed behaviour of the free-piston movement is the key to an expander performance. In this paper, we have proposed an idea of reducing complexity of the free-piston expander. It is to replace both multiple solenoid valves and reservoirs that are indispensable in a previous machi...

This research paper focuses on the experimental investigation of the Stirling-type pulse tube refrigerator with cold compression concept. Due to this innovative feature, the pulse tube refrigerator can reach lower temperature effectively other typical single-stage Stirling-type pulse tube refrigerators. The experiment as a proof of concept is carri...

This research paper focuses on the development of the Stirling-type pulse tube refrigerator (PTR) system. The system includes an innovative cold compression concept by introducing a superconducting linear compressor (SCLC). As one of the key goals of this research, the working gas (helium) is to be compressed directly at cryogenic temperature. The...

Fast magnetic field alternation is indispensable for continuous magnetic refrigeration. An active magnetic regenerative refrigerator (AMRR) utilizes magnetocaloric effect (MCE) of magnetic materials which occurs during magnetization and demagnetization processes. A conduction cooled high temperature superconducting (HTS) magnet can be one of the pr...

A cryogenic Joule-Thomson (JT) refrigerator has many advantages for large industrial applications, including easy cooling power adjustability and high reliability because there are no moving parts at low temperature. In this paper, a single stage and a cascade type of non-flammable (NF) mixed refrigerant (MR) JT refrigerators have been proposed for...

This paper describes the cryogenic chill-down experiments that are conducted on a 12.7 mm outer diameter, 1.25 mm wall thickness and 7 m long stainless steel horizontal pipe with liquid nitrogen (LN2). The pipe is vacuum insulated during the experiment to minimize the heat leak from room temperature and to enable one to numerically simulate the pro...

Generally, a part of transporting liquids are used as the coolant to chill down the transfer line. Minimizing the line chill-down time and the consumption of the cryogenic propellant during the line chill-down is a mainly concerned issue. In this study, the cryogenic line chill-down experiments are conducted on a 12.7 mm outer diameter, 1.25 mm wal...

A free-piston reciprocating expander is a device which operates without any mechanical linkage to a stationary part. Since the motion of the floating piston is only controlled by the pressure difference at two ends of the piston, this kind of expander may indispensably require a sophisticated active control system equipped with multiple valves and...

In this paper, a cascade type non-flammable mixed refrigerant (MR) Joule-Thomson (JT) refrigerator is suggested to achieve 100 K cooling temperature. The working fluid utilized in the main stage (low temperature cycle) of the MR JT refrigerator is composed of nitrogen (N2), argon (Ar), Tetrafluoromethane (R14) and Octafluoropropane (R218). An azeot...

An active magnetic regenerator (AMR) system requires fast ramp rate of magnetic field variation. The magnetic field change enables a magnetic refrigerant to create magnetocaloric effect for magnetic refrigeration. In this paper, a conduction-cooled high-temperature superconducting (HTS) magnet has been thermally analyzed and tested for an AMR syste...

Non-flammable mixed refrigerant (NF-MR) Joule Thomson (J-T) refrigerators have desirable characteristics and wide cooling temperature range compared to those of pure J-T refrigerators. However, the operating challenge due to freezing is a critical issue to realize this type of refrigerator. In this paper, the solid-liquid phase equilibria (i.e. fre...

Gauging the volume or mass of liquid propellant of a rocket vehicle in space is an important issue for its economic feasibility and optimized design of loading mass. Pressure-volume-temperature (PVT) gauging method is one of the most suitable measuring techniques in space due to its simplicity and reliability. This paper presents unique experimenta...

The powder insulation method is widely used in structural and cryogenic systems such as transportation and storage tanks of cryogenic fluids. The powder insulation layer is constructed by small particle powder with light weight and some residual gas with high porosity. So far, many experiments have been carried out to test the thermal performance o...

The performance of a two-stage layered AMRR is experimentally investigated. The test apparatus includes two-stage layered AMRs, low temperature superconducting (LTS) magnet which generates maximum magnetic field of 4 T, and the helium gas flow system. The helium compressor with the tandem rotary valve is employed to generate the oscillating flow of...

This research paper focuses on the performance prediction and its validation via experimental investigation of a Stirling-type pulse tube refrigerator (PTR) equipped with a cold linear compressor. When the working gas is compressed at cryogenic temperature, the acoustic power (PV power) can be directly transmitted through the regenerator to the pul...

In this paper, a tandem-type pulse tube refrigerator without a reservoir is discussed and investigated. For its practical application a tandem-type compressor is designed to generate two pulsating pressure waves with opposite phases, simultaneously. A tandem-type pulse tube refrigerator consists of a tandem-type compressor and two identical pulse t...

The adiabatic demagnetization refrigerator (ADR) system in this paper is composed of a conduction-cooled alternating current (AC) high-temperature superconducting (HTS) magnet system, a magnetic bed assembly, its heat exchange parts and an auxiliary precooling stage (a commercial GM cryocooler and a liquid nitrogen vessel). The whole magnetic refri...

High-temperature superconducting (HTS) cable is one of the most prospective superconducting technologies for its low electric power transmission loss and high power density. One difficulty of practicing this technology is maintaining the HTS cable at a cryogenic temperature approximately at 70 K. The types of cryogenic refrigerators are briefly rev...

Magnetic refrigeration requires a strong magnetic field and its alternation for the magnetization and demagnetization processes. A conduction-cooled (RE)BCO coil was designed and fabricated to exert the maximum central magnetic field of 3.5 T with a field homogeneity of 90% on the magnetic refrigerant bed for an adiabatic demagnetization refrigerat...

The design procedure of an active magnetic regenerator (AMR) operating between liquid nitrogen temperature and liquid hydrogen temperature is discussed with the selected magnetic refrigerants. Selected magnetic refrigerants (GdNi2, Dy0.85Er0.15Al2, Dy0.5Er0.5Al2, and Gd0.1Dy0.9Ni2) that have different transition temperatures are layered in an AMR t...

For a long-term space mission, filling process of cryogenic liquid propellant is operated on a space vehicle in space. A vent process during transfer and filling of cryogenic propellant is needed to maintain the fuel tank pressure at a safe level due to its volatile characteristic. It is possible that both liquid and vapor phases of the cryogenic p...

Mixed refrigerant Joule Thomson refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multi-phase and multi-component fluid in the cryogenic temperature range is necessarily required in the heat exchanger design of mixed refrigerant Joule Thomson refrigerators, it has bee...

This paper discusses the fabrication of a (RE)BCO solenoid magnet and its experimental results from the aspect of AC loss and thermal characteristics. A (RE)BCO coated conductor with polyimide tape insulation was utilized for a coil and wound by a standard layer-wound method. The (RE)BCO solenoid magnet consists of a stainless steel bore and a pair...

Cryoablation is a surgical procedure used to freeze defective cells by inserting a low temperature probe into a human body to destroy malignant tissues. Miniaturized Joule-Thomson (J-T) refrigerators are often used to minimize the volume of the cooling device and reduce the destruction zone of normal tissue. The cooling effects of the existing prob...

Magnetic refrigeration requires a strong magnetic field and its alternation for the magnetization and demagnetization processes. In this paper, a conduction-cooled HTS magnet system was fabricated and tested for a magnetic refrigerator. It consists of a HTS magnet, a pair of metallic and HTS current leads, and a cryocooler. The Gd-Ba-Cu-O coated co...

The submerged helium injection process results in the heat and mass transfer between the helium bubble and the cryogenic liquid. The objective of this paper is to analyze the dynamics of the heat and mass transfer process. It is observed that during the helium injection process the dynamics of mass transfer is dominant and the transient heat transf...

Since glass microsphere has high crush strength, low density and small particle size, it becomes alternative thermal insulation material for cryogenic systems, such as storage and transportation tank for cryogenic fluids. Although many experiments have been performed to verify the effective thermal conductivity of microsphere, prediction by calcula...

When a compact microchannel heat exchanger is operated at cryogenic environments, it has potential problems of axial conduction and flow maldistribution. To analyze these detrimental effects, the heat exchanger model that includes both axial conduction and flow maldistribution effect is developed in consideration of the microchannel heat exchanger...

Carbon dioxide (CO2) is one of the dominant gas molecules that causes greenhouse effect, i.e. global warming. Numerous studies have been carried out to regulate the emission of CO2 to reduce greenhouse gas. The liquid CO2 is a convenient form of transportation compared to high-pressurized gaseous CO2. Therefore, the direct liquefaction mechanism of...

An active magnetic regenerative refrigerator (AMRR) is expected to be useful for hydrogen liquefaction due to its inherent high thermodynamic efficiency. Because the temperature of the cold end of the refrigerator has to be approximately liquid temperature, a large temperature span of the active magnetic regenerator (AMR) is indispensable when the...

Mixed Refrigerant Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. Printed Circuit Heat Exchanger (PCHE) is one of the promising cryogenic compact recuperators for MR-JT refrigerators due to its compactness, high NTU and robustness. However, PCHE composed with microchannel bundles can cause flow...

A 2-stage mixed refrigerant (MR) Joule-Thomson (JT) cryocooler was designed for cooling high temperature superconducting cable below 70 K. The low temperature cycle was to operate with neon-nitrogen mixture, and the required compression ratio was approximately 24 when the suction pressure was 100 kPa. The high compression ratio of 24, the low press...

Mixed Refrigerant Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. Although heat transfer coefficient estimation for a multiphase and multi-component fluid in cryogenic temperature range is necessarily required in the heat exchanger design of MR-JT refrigerator, it has been rarely discussed so fa...

This paper presents an experimental investigation on a magnetic refrigerator operating between 77 K and 20 K. Since the magneto-caloric effect of typical magnetic refrigerant is concentrated in a narrow temperature region, four different rare-earth intermetallic compounds (GdNi2, Dy0.85Er0.15Al2, Dy0.5Dr0.5Al2, and Gd0.1Dy0.9Ni2) are utilized accor...

Cryoablation device is a surgical instrument to produce the cooling effect to destroy detrimental biological tissue by utilizing low temperature around 110 K. Usually, this device has the concentrated cooling region, so that it is suitable for concentrated and thick target. Accordingly, it is hard to apply this device for the target which is distri...

In this paper, the development of the tandem reciprocating room-temperature active magnetic regenerative refrigerator and the numerical simulation for the effect of the dead volume are presented. The dead volume effect is analyzed by establishing a onedimensional time-dependent model for the active magnetic regenerator (AMR). The cooling power at t...

This paper describes thermal packaging issues of YBCO high-temperature superconductor (HTS) bulk for SFES (superconducting flywheel energy storage) system. For stable operation of the superconducting bearing, the temperature of HTS bulk needs to be maintained below 70 K by a cryocooler system where thermal radiation from room temperature environmen...

Mixed refrigerant Joule–Thomson (MR J–T) cryocoolers have been used to create cryogenic temperatures and are simple, efficient, cheap, and durable. However, compressors for MR J–T cryocoolers still require optimization. As the MR J–T cryocooler uses a commercial scroll compressor developed for air-conditioning systems, compressor overheating due to...

Configurations and performances of a pulse tube engine are devised and investigated in this paper. Energy flow concept and mechanical–acoustical analogy enable one to design several different types of pulse tube engine. They are classified as a pulse tube engine equipped with two pistons or one piston and a tandem pulse tube engine. Specially, the...

Mixed Refrigerant-Joule Thomson (MR-JT) refrigerators are widely used in various kinds of cryogenic systems these days. The temperature glide effect is one of the major features of using mixed refrigerants since a recuperative heat exchanger in a MR-JT refrigerator is utilized for mostly two-phase flow. Although a pressure drop estimation for a mul...

Shuttle heat transfer loss is one of the losses generated in a pulse tube and considerably influences the performance of a pulse tube refrigerator. If the inner wall of a pulse tube is perfectly maintained at adiabatic condition, the shuttle heat transfer loss can be eliminated. Near adiabatic condition may be achieved in the inner wall of a pulse...

LNG (Liquefied Natural Gas) offloading process from LNG cargo to storage tank includes substantial vertical upward fluid transportation. During this LNG transportation process, local boiling may occur at elevated position of the transport pipe due to the decrease of hydrostatic pressure and obstruct liquid flow, concluding long transport time or in...

This paper presents the results of an experimental investigation of the thermal and hydraulic performance of a printed circuit heat exchanger (PCHE) for use in the cryogenic temperature region. Compact PCHEs with multiple corrugated, longitudinal flow microchannels were fabricated using chemical etching and diffusion bonding to evaluate their therm...

This paper presents an improved design method and performance prediction of Stirling-type pulse tube refrigerator (PTR). The paper is composed of three parts and each content is as follows: 1) specific design and fabrication of each component, 2) modeling and configuration optimization of Stirling-type PTR, and 3) experimental verification. Each pa...

The analysis of energy flow is a useful method for understanding a system. This paper focuses on the instantaneous measurement of physical conditions and analysis of energy flow in the Stirling-type pulse tube refrigerator. For measuring physical conditions of the working fluid such as the mass flow rate, the temperature, and the pressure, several...

PCHE (Printed Circuit Heat Exchanger) is one of the promising cryogenic compact heat exchangers due to its compactness, high NTU and robustness. The essential procedure for fabricating PCHE is chemical etching and diffusion bonding. These technologies can create sufficiently large heat transfer area for a heat exchanger with numerous micro channels...

PVT gauging method is simple and reliable to gauge the remaining quantity of cryogenic propellant under microgravity. This paper presents the results of novel analysis of pressure-volume-temperature (PVT) gauging method. Experimental re-sults using LN2 are analyzed by a novel PVT gauging analysis which considers all instantaneous changes of pressur...

This paper proposes and describes a compact work-recovery phase shifter of a pulse tube refrigerator. Most pulse tube refrigerators recently developed utilize a long inertance tube and a reservoir for phase control between dynamic pressure and mass flow rate at the cold-end of pulse tube refrigerators. An inertance tube-type phase shifter (long ine...

High-performance multi-channel heat exchangers are vulnerable to small defects such as ill-manufacture or contamination in flow channels. Even slight flow mal-distribution may result in drastic reduction of their thermal performance. In order to accommodate such performance reduction in multi-channel heat exchangers, transverse bypass structure amo...

The substitution of high temperature superconducting (HTS) cables for existing subterranean electric transmission lines is arising as a solution to continuously increasing electricity demand in urban areas. A cryogenic refrigeration system having the characteristics of high reliability, high efficiency, large cooling capacity, and low capital cost...

A cryogenic refrigeration system is one of the indispensable components for cooling superconducting motor or generator. Among various configurations of cryogenic refrigeration system, the on-board refrigeration system is considered to be attractive for compactness and small heat leak. In order to turn this concept into reality, we focus on two esse...