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It is very important to keep the freshness up of fish product because fish will quickly decay after it is caught. Ice slurry is one of the best cooling mediums generated through refrigeration system utilizing sea water as its base material. Ice slurry can keep the freshness and also increase the lifetime of the fish product, because ice slurry suppresses bacterial decomposition rate. In this study, the production rate of the ice slurry generator coated by teflon was investigated. The rotational speed of the pump and scrapper were varied at 1064 – 1242 RPM and 335 – 423 RPM. The sea water was also varied at 10 ppt – 27 ppt. The optimum production rate of ice slurry and salinity variation has been obtained. Increasing the rotational speed of pump and scrapper with higher water salinity of seawater will decrease production rate of ice slurry. It was found that the best production rate of slurry ice generator in this research was 0.284 Ton/12 Hours produced by 10 ppt salinity of seawater with 335 RPM rotation on the scraper and 1064 RPM on the pump. Ice slurry could be a good option for long shipping time by keeping the fish quality.

Spray dryers are commonly operated at a high temperature (>100 °C), which becomes an obstacle for heat-sensitive materials. In this study, a refrigeration system that uses evaporator as dehumidifier and that recovers the heat released from the first condenser to preheat the drying air was utilised to reduce the drying temperature. Results showed that the degradation of vitamin A (measured with the high performance liquid chromatography method) in tomato increased significantly when the drying air temperature increased from 90 °C to 120 °C, and it cannot be controlled at a temperature higher than 120 °C. At an air flow rate of 450 lpm, the drying capacity at a drying air temperature of 60 °C (with refrigeration, humidity ratio of 0.005 [kg H2O / kg dry air]) is equal to the drying capacity at a drying air temperature of 120 °C (without refrigeration, humidity ratio of 0.021 [kg H2O / kg dry air]). The drying capacity at a drying air temperature of 90 °C (with refrigeration) even becomes 1.5 times the dryin...

Condensation is the change of physical state of matter from gas phase into liquid phase. Condensation occurs whenever a vapor comes into contact with a surface at a temperature lower than the saturation temperature corresponding to its vapor pressure. Condensation is an effective way of transferring heat and widely used in power plants, refrigeration and air-conditioning system, water desalination, petroleum industry, chemical production plant, etc. Performance of condensation heat transfer depends on many factors including surface material, surface morphology, degree of sub-cooling, characteristics of the fluid, presence of impurities, etc. Among different properties, surface characteristics is an easy way to modify to enhance the condensation heat transfer. In this paper surface characteristics of the solid surface has been modified with square shaped micro grooves of 500×500 µm dimension along the length of the plate. With this modified micro-grooved copper plate condensation experiment has been conducted and the experimental results are compared with that of the flat copper plate. Heat transfer performance for the modified surface is observed to increase by 30%-40% compared to that of the flat surface. A parametric analysis is also conducted by varying the flow rate of the cooling fluid and surface temperature of the cooper plate. Plausible reason for this enhancement also has been discussed in this paper.

The efficiency impact analysis of the heat exchangers included in the mobile compressor unit (MCU) heat losses recovery system (HLRS) on the overall system operation efficiency on the basis of the refrigeration unit applying was conducted in the paper. The study subject is the mobile compressor unit (MCU) driven by the internal combustion engine and heat losses recovery system based on the cooling loop. The research scope is the unit energy efficiency.The efficiency impact analysis of the heat exchangers included in the mobile compressor unit (MCU) heat losses recovery system (HLRS) on the overall system operation efficiency on the basis of the refrigeration unit applying was conducted in the paper. The study subject is the mobile compressor unit (MCU) driven by the internal combustion engine and heat losses recovery system based on the cooling loop. The research scope is the unit energy efficiency.

This paper introduces the working principle and system constitution of the linear Fresnel solar lithium bromide absorption refrigeration cycle, and elaborates several typical structures of absorption refrigeration cycle, including single-effect, two-stage cycle and double-effect lithium bromide absorption refrigeration cycle A 1.n effect absorption chiller system based on the best parameters was introduced and applied to a linear Fresnel solar absorption chiller system. Through the field refrigerator performance test, the results show: Based on this heat cycle design and processing 1.n lithium bromide absorption refrigeration power up to 35.2KW, It can meet the theoretical expectations and has good flexibility and reliability, provides guidance for the use of solar thermal energy.This paper introduces the working principle and system constitution of the linear Fresnel solar lithium bromide absorption refrigeration cycle, and elaborates several typical structures of absorption refrigeration cycle, including single-effect, two-stage cycle and double-effect lithium bromide absorption refrigeration cycle A 1.n effect absorption chiller system based on the best parameters was introduced and applied to a linear Fresnel solar absorption chiller system. Through the field refrigerator performance test, the results show: Based on this heat cycle design and processing 1.n lithium bromide absorption refrigeration power up to 35.2KW, It can meet the theoretical expectations and has good flexibility and reliability, provides guidance for the use of solar thermal energy.

A performance analysis based on exergetic performance coefficient (EPC) criterion was carried out for a dual-evaporator vapor compression refrigeration system. The influence of the condensing and evaporating temperature on the EPC, the coefficient of performance (COP), the second law efficiency and the destruction of exergy will be presented. It is found that the evaporating and condensing temperatures have strong effects on EPC in the system. Condensing temperature increases will decrease EPC, COP, and second law efficiency, while evaporating temperature increases will increase the EPC, COP, and second law efficiency. The EPC increases and the total exergy destruction decreases with decreasing temperature difference between the evaporator and refrigerated space and between the condenser and ambient temperature. The EPC can be used for selection of optimal design parameters and the procedures given in this paper for exergy analysis of a dual evaporator vapor compression refrigeration systems has been applied to actual systems.A performance analysis based on exergetic performance coefficient (EPC) criterion was carried out for a dual-evaporator vapor compression refrigeration system. The influence of the condensing and evaporating temperature on the EPC, the coefficient of performance (COP), the second law efficiency and the destruction of exergy will be presented. It is found that the evaporating and condensing temperatures have strong effects on EPC in the system. Condensing temperature increases will decrease EPC, COP, and second law efficiency, while evaporating temperature increases will increase the EPC, COP, and second law efficiency. The EPC increases and the total exergy destruction decreases with decreasing temperature difference between the evaporator and refrigerated space and between the condenser and ambient temperature. The EPC can be used for selection of optimal design parameters and the procedures given in this paper for exergy analysis of a dual evaporator vapor compression refrigeration systems has been appl...

In this paper, a physical method to obtain control-oriented dynamical models of large scale cryogenic refrigerators is proposed, in order to synthesize model-based advanced control schemes. These schemes aim to replace classical user experience designed approaches usually based on many independent PI controllers. This is particularly useful in the case where cryoplants are submitted to large pulsed thermal loads, expected to take place in the cryogenic cooling systems of future fusion reactors such as the International Thermonuclear Experimental Reactor (ITER) or the Japan Torus-60 Super Advanced Fusion Experiment (JT-60SA). Advanced control schemes lead to a better perturbation immunity and rejection, to offer a safer utilization of cryoplants. The paper gives details on how basic components used in the field of large scale helium refrigeration (especially those present on the 400W @1.8K helium test facility at CEA-Grenoble) are modeled and assembled to obtain the complete dynamic description of controll...

Applications in superconductivity have become widespread, enabled by advancements in cryogenic engineering. In this paper, the history of cryogenic refrigeration, its delivery, its preservation and the important scientific and engineering advancements in these areas in the last 100 years will be reviewed, beginning with small laboratory dewars to very large scale systems. The key technological advancements in these areas that enabled the development of superconducting applications at temperatures from 4 to 77 K are identified. Included are advancements in the components used up to the present state-of-the-art in refrigeration systems design. Viewpoints as both an equipment supplier and the end-user with regard to the equipment design and operations will be presented. Some of the present and future challenges in these areas will be outlined. Most of the materials in this paper are a collection of the historical materials applicable to these areas of interest.

Ball Aerospace and Redstone Aerospace are developing a space cryocooler for cooling complex optical systems whose loads are intermittent. An example of such a system would be an Earth observation satellite that images for only a fraction of its orbit. If a cooler can store refrigeration during the lull and provide it when the system is active, the cooler can be considerably smaller than one sized to provide the full load continuously. Our cooler provides two stages of refrigeration, a stage of intermittent cooling at 35 K for a focal plane assembly and a stage of continuous cooling at 85 K for the surrounding thermal shields. The cooler provides the intermittent cooling by collecting liquid neon in a unique internal thermal storage tank and forwarding it to the focal plane when the heat loads are high. Our paper presents extensive performance data for neon at 35 K. It carries 2 W at 35 K for 30 minutes plus the 8.5 W of continuous cooling at 85 K for less than 300 W DC power. It is ready to cool again in an hour. For contrast, the same hardware was filled with nitrogen and tested at 82 K. It carries 5 W for 25 minutes plus 15 W of continuous cooling at 130 K for less than 220 W DC power. It is ready to cool again in a little over an hour. The system has many features for space system compatibility. Because the storage is located within an active control loop, the cooler can maintain the 35 K interface temperature to better than ± 0.1 K. Because it circulates liquid it can be located remotely, which solves many compatibility issues. And with careful liquid management, it can work in any orientation and in 0-g. In this paper our flight like equipment will be described, and its continuing evolution to flight will be discussed.

This paper is offered as a response to the remarks regarding [1], as given in [2].This paper is offered as a response to the remarks regarding [1], as given in [2].

The CEA is involved in large helium refrigeration applied to the future experimental fusion reactors (e.g. ITER or JT‐60SA). Pulsed operation of such machines results in heat load variations which the refrigerators have to cope with. One solution to smooth pulsed loads is to use a large thermal buffer, and in the case of JT‐60SA cryogenic system, a saturated thermal bath is one of the investigated solutions. A 1D thermo hydraulic model describing the cooling loop associated with TF (Toroidal Field) coils and TF casing has been developed using Vincenta code to calculate the heat load arriving to the buffer (saturated bath). However, the liquid helium buffer itself and its coupling with the primary loop was not modelized. This paper shows results obtained using the existing functionalities in Vincenta code to model a saturated bath. For very large bath volumes, bath temperature remains almost steady and the power removed is equal to those previously calculated. On the other side, for smaller buffer volumes (e.g. JT‐60SA scheme), it has been found that the increase of temperature fluctuations does not vary proportionally with the decrease of the buffer volume.The CEA is involved in large helium refrigeration applied to the future experimental fusion reactors (e.g. ITER or JT‐60SA). Pulsed operation of such machines results in heat load variations which the refrigerators have to cope with. One solution to smooth pulsed loads is to use a large thermal buffer, and in the case of JT‐60SA cryogenic system, a saturated thermal bath is one of the investigated solutions. A 1D thermo hydraulic model describing the cooling loop associated with TF (Toroidal Field) coils and TF casing has been developed using Vincenta code to calculate the heat load arriving to the buffer (saturated bath). However, the liquid helium buffer itself and its coupling with the primary loop was not modelized. This paper shows results obtained using the existing functionalities in Vincenta code to model a saturated bath. For very large bath volumes, bath temperature remains almost steady and the power removed is equal to those previously calculated. On the other side, for smaller buffer volumes ...

The James Webb Telescope is the successor to the Hubble Telescope and will be placed in an orbit of 1.5 million km from earth. Before launch in 2014, the telescope will be tested in NASA Johnson Space Center’s (JSC) space simulation chamber, Chamber A. The tests will be conducted at deep space conditions. Chamber A’s helium cryo‐panels are currently cooled down to 20 K by two Linde 3.5 kW helium refrigerators. The new 12.5 kW, 20‐K helium coldbox described in this paper is part of the upgrade to the chamber systems for this large test program. The Linde coldbox will provide refrigeration in several operating modes where the temperature of the chamber is being controlled with a high accuracy due to the demanding NASA test requirements. The implementation of two parallel expansion turbine strings and the Ganni cycle—Floating Pressure process results in a highly efficient and flexible process that minimizes the electrical input power. This paper will describe the collaboration and execution of the coldbox project.

Evaporating falling film on horizontal tubes has been widely used in desalinization, refrigeration, chemical process industries, and so on. In this paper, the flow characteristics of falling film outside horizontal tubes in horizontal air flows was studied theoretically and experimentally. Two low patterns of the falling film, i.e., droplet flow pattern and columnar flow pattern, were considered. Effects of the velocity of airflow, the flux of falling film flow, the external diameter of tube and the surface property of tube on the falling film flowing characters were investigated. Experimental study indicated that, in a definite flow scale, as the flow increased, the diameters of falling droplets and falling columns of the liquid enlarged, and the liquid film became thick and the area covered by the liquid film increased. As the air velocity increased, the offset of the droplet and the column to the top of the tube enlarged, and the rate of increase come down until it complete depart from the the top of the horizontal tube. Besides, a theoretical model was established about the offset of the droplet and liquid column from the top of the tube under the force of the horizontal air flows, and the model was validated by a comparison between the numerical predictions and experimental data.A further analysis about the excursion law of falling film flow outside horizontal tube was also made at the last paprt of the paper.

This paper is an update of papers written in 1991 and in 1997 by Rod Byrns and this author concerning estimating the cost of refrigeration for superconducting magnets and cavities. The actual costs of helium refrigerators and coolers (escalated to 2007 dollars) are plotted and compared to a correlation function. A correlation function between cost and refrigeration at 4.5 K is given. The capital cost of larger refrigerators (greater than 10 W at 4.5 K) is plotted as a function of 4.5-K cooling. The cost of small coolers is plotted as a function of refrigeration available at 4.2 K. A correlation function for estimating efficiency (percent of Carnot) of both types of refrigerators is also given.

Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately 1 kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. Subsequent testing may also be performed in-flight on an Air Force transport aircraft.Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately 1 kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. ...

A single‐stage coaxial pulse tube refrigerator has been designed for HTS (High Temperature Superconductor) motor application. This paper discusses a practical realization of an advanced cooling method for superconducting rotor, on‐board cryocooler. When a cryocooler is considered to be mounted on the superconducting rotor, the following two factors must be satisfied for practical application. First, the on‐board cryocooler should not disturb the high‐speed revolution of the rotor. Second, at the same time, the high‐speed revolution of the rotor should not deteriorate the cooling performance of the cryocooler. These mutual technical demands restrict the type of cryocooler suitable for high‐speed rotating environment. We select a Stirling‐type coaxial pulse tube cryocooler and incorporate it on the 1800‐rpm superconducting motor mock‐up. The pulse tube cryocooler is designed with an adiabatic model and a various loss mechanism analysis. The no‐load temperature is approximately 100 K with less than 150 W electric input power. The axisymmetric configuration of the fabricated cryocooler does not produce any undesirable effect at high‐speed rotation. Even if the thermal performance of the rotating pulse tube cryocooler is not satisfactory, the feasibility of simple on‐board cooling method for superconducting rotor is confirmed in this paper.

This paper describes the design, development, testing and performance at Ball Aerospace of a long life, 4–6 K temperature space cryocooler. For temperatures to 4 K and below, Ball has developed a hybrid Stirling/ Joule‐Thomson (J‐T) cooler. The hybrid cooler has been verified in test to 3.5 K on a Ball program and a 6 K Development Model is in development on the NASA/JPL Advanced Cryocooler Technology Program (ACTDP). This paper will include the test status on the Stirling Precooler and the Thermal System Breadboard. The ACTDP cooler provides simultaneous cooling at 6 K (typically, for either doped Si detectors or as a sub‐Kelvin precooler) and 18 K (typically, for optics or shielding) with cooling stages also available at 40 and 180 K (typically, for thermal shields or other components). The ACTDP cooler is under development for the NASA Terrestrial Planet Finder (TPF), Constellation X‐Ray (Con‐X), and other future missions. The 4–6 K cooler is highly leveraged off previous Ball space coolers including multiple life test and flight units.

An ongoing program at Brookhaven National Laboratory (BNL) consists of improving the efficiency of the Relativistic Heavy Ion Collider (RHIC) cryogenic system and reducing its power consumption. Phase I and II of the program addressed plant operational improvements and modifications that resulted in substantial operational cost reduction and improved system reliability and stability, and a compressor input power reduction of 2 MW has been demonstrated. Phase III, now under way, consists of plans for further increasing the efficiency of the plant by adding a load “wet” turbo‐expander and its associated heat exchangers at the low temperature end of the plant. This additional stage of cooling at the coldest level will further reduce the required compressor flow and therefore compressor power input. This paper presents the results of the plant characterization, as it is operating presently, as well as the results of the plant simulations of the various planned upgrades for the plant. The immediate upgrade includes the changes associated with the load expander. The subsequent upgrade will involve the resizing of expander 5 and 6 to increase their efficiencies. The paper summarizes the expected improvement in the plant efficiency and the overall reduction in the compressor power.

A high Tc superconducting (HTS) magnet excited by a thermal electromotive force of a thermoelectric element is studied. This HTS magnet has the advantages of compactness, lightweight and continuous excitation in comparison with conventional HTS magnets, because this HTS magnet does not need a large external power source. In this system, a heat input into the cryogenic environment is necessary to excite the thermoelectric element for constant operation. This heat generation, however, causes a rise in temperature of an HTS coil and reduces the system performance. In this paper, a newly designed magnet system which adopted a two‐stage GM cryocooler was investigated. It enabled us to control the temperature of a thermoelectric element and that of an HTS coil independently. The temperature of the HTS coil could be kept at 10–20 K at the second stage of the GM cryocooler, while the thermoelectric element could be excited at higher temperature in the range of 50–70 K at the first stage, where the performance of the thermoelectric element was higher. The experimental results on this HTS magnet are shown and the possibility of the thermoelectric element as a main power source of the HTS magnets is discussed.A high Tc superconducting (HTS) magnet excited by a thermal electromotive force of a thermoelectric element is studied. This HTS magnet has the advantages of compactness, lightweight and continuous excitation in comparison with conventional HTS magnets, because this HTS magnet does not need a large external power source. In this system, a heat input into the cryogenic environment is necessary to excite the thermoelectric element for constant operation. This heat generation, however, causes a rise in temperature of an HTS coil and reduces the system performance. In this paper, a newly designed magnet system which adopted a two‐stage GM cryocooler was investigated. It enabled us to control the temperature of a thermoelectric element and that of an HTS coil independently. The temperature of the HTS coil could be kept at 10–20 K at the second stage of the GM cryocooler, while the thermoelectric element could be excited at higher temperature in the range of 50–70 K at the first stage, where the performance of ...

This paper describes the HIRDLS (High Resolution Dynamic Limb Sounder) Cryocooler Subsystem (CSS) and its on‐orbit flight performance. The HIRDLS Instrument was launched on July 15, 2004 as part of the NASA GSFC EOS Aura platform. Ball Aerospace provided the CSS, which includes the long life Stirling cryocooler (cooling at 59 K), cold plumbing to connect the cooler to the instrument Detector Subsystem, an ambient radiator to reject the cooler dissipation, and a vacuum enclosure system that enabled bench top ground testing. As of August 20, 2005, the cryocooler has over 9,000 hours of continuous operation with performance that exceeds requirements. Of note is that the CSS has experienced virtually no change in performance, including no indication of external contamination related degradation that has been evident on several other cryocooler systems in space flights. This steady performance can be attributed to the multi‐layer insulation (MLI) based insulation design, which will be described in the paper.

At present, much interest is being shown in hybrid absorption refrigeration cycles driven by low temperature heat sources, such as solar energy or low-grade waste-heat. In the present work, an exergetic investigation of a novel configuration double-lift absorption/compression refrigeration system is developed. The potential of the organic mixture (R236fa/DMAC) in the low grade heat pump is discussed. In this paper, a modeling and simulation of the proposed configuration is presented. The ammonia-water system was used for comparison purposes. The results show that the performances of the proposed configuration are improved significantly when using the above mentioned organic mixture. Coefficient of performance of the cycle with R236fa/DMAC is 15% higher than with ammonia/water. Exergetic performances of the system are also improved by about 10% with the use of the proposed new mixture. The most important result given in this study is that the above system operates at low generator temperatures between 50°C and 80°C, which makes it a good alternative of the ammonia-water systems in the low grade heat refrigeration field. The use of such an organic fluid makes it possible to adapt the machine to sources of low energy value, among the possible solutions it was considered to install a hybrid photovoltaic unit that will meet the electrical needs of the heat pump. A simulation was also done to consolidate the results.Results of such a system show that the energy demand of absorption / compression refrigeration machines can be insured by about 80 % by solar energy.The proposed model is efficient in predicting the performance of the machine at different working conditions such as: temperature variation of the generator and evaporator, change in climatic conditions…To conclude, this study will allow making an economic optimization, an approximation on the lifetime as well as the annual production capacity of the unit.

Due to environmental concerns the refrigeration system has been changed from chlorofluorocarbon (CFC) refrigerant to hydrofluorocarbon (HFC) refrigerant. Because of the absence of chlorine in HFC refrigerant, a protective layer of ferrous chloride could not form on the interface which could limit the operating conditions (e.g. pressure) and results in a worse wear performance of compressor’s material in HFC refrigerant. However, the compressor (interface material) must be able to withstand severe operating conditions in the corrosive gaseous environment. However, few works have been done on the effect of HFC refrigerants on tribological behavior of materials. This paper aims to investigate the tribological properties of a commonly used compressor material carbon steel – MN 4.9 under dry, CFC (R22) and HFC (R134a) refrigerant lubrication conditions. It was found that the wear resistance and friction coefficient of the carbon steel increased when the test was performed under the HFC refrigerant environment. A protective layer/oxide layer could have formed on the material during sliding in the refrigerant condition that enhances the wear resistance. The material showed better wear resistance in R22 refrigerant indicating that a ferrous chloride layer had formed on the wear track. Electron microscopy revealed that the wear track after sliding at dry condition contains abrasion marks indicating typical abrasive wear. The wear track after sliding in R134a shows severely deformed material, ploughed groove and shared material indication ploughing is the main wear mechanism.

The purpose of this paper is to examine energy efficiency through the study of performance in vapour compression cycle for auditorium in University of Indonesia using natural refrigerant R290. The installation of the chiller system which is the first in Indonesia within academic institution is particularly relevant in light of the gaining interest and research regarding the implementation of refrigeration system utilizing relatively low ODP and GWP refrigerant as alternative to replace the refrigerant HCFC-22. It is found that the highest COP during 64% partial cooling load is 4.27 at temperature water inlet is 8.9°C. The maximum COP during 75% partial load is 5.25 at temperature water inlet is 6,8 °C. The cooling capacity are 125.93 kW and 148.39 kW during 64% and 75% load, respectively.

The problem of heat damage in high temperature mine has been attached more and more concern to. In addition, the existing solutions also have problems which are large initial investment and poor safety performance. Vortex tube type of mine cooling jacket, studied in this paper, using vortex tube refrigeration principle. It used compressed exhaust gas as the gas source, which can solve the problem of the large-scale cooling equipment which rely on electricity, and may not emit toxic gases at the same time. Thereby, by using the method of observation and questionnaire survey, the parameters of the vortex tube were optimized for optimal cooling effect. In conclusion, the features of security, reliability, energy saving and environmental protection can be realized by the vortex tube type of cooling jacket. What’s more important, we had investigated the feasibility of the application of vortex tube type of mine cooling jacket.

This paper presents the performance of a solar hybrid desiccant air-conditioning system that was tested in a humid and hot weather of Malaysia. The system is consisted of a desiccant wheel, a solar thermal collector, a vapour compression refrigeration cycle and a heat pipes heat exchanger. In this system, the latent heat load of supply air was removed by a silica-gel desiccant wheel which was regenerated by a 31.5 m2 evacuated tube solar collector assisted by an auxiliary heater. The sensible heat load was removed by pre-cooled the supply air using vertical heat pipes (act as a heat recovery system) before the air temperature is further reduced by a cooling coil connected to a conventional vapour compression cycle. Through the test, the supply and exhaust (regeneration) mass flow rate of air were maintained at 450 m3/hr. The Coefficient of Performance (COP), effectiveness of desiccant wheel and heat pipe were 1.42, 0.61 and 0.54, respectively. Reduction in energy consumption was estimated at 62% relative to a system without a desiccant wheel and heat pipe heat exchanger. It can be concluded that this system can provide supply air at a temperature of 23.4 °C and specific humidity of 0.011 (kg/kg) with a significantly less energy consumption in a hot and humid weather of Malaysia.

The new 4.5 K refrigerator system added to the Jefferson Lab (JLab) Central Helium Liquefier (CHL) for the 12 GeV upgrade will double its previous capacity. It includes a 4.5 K cold box system and compressor system with associated oil removal and gas management systems. At its maximum capacity condition, this new system supports an additional 238 g/s 30 K 1.16 bar cold compressor return flow, a 15 g/s 4.5 K liquefaction load and a 12.6 kW 35–55 K shield load. Five more design conditions, ranging from liquefaction to refrigeration and a stand-by/reduced load state, were specified for the sizing and selection of its components. The cold box system is comprised of a 300–60 K vertical cold box that incorporates a liquid nitrogen pre-cooler and a 60–4.5 K horizontal cold box housing seven turbines that are configured in four expansion stages including one Joule-Thompson expander. The helium compression system has five compressors to support three pressure levels in the cold box. This paper will briefly review the salient 4.5 K system design features and discuss the recent commissioning results.

Small scale thermoacoustic heat engines have advantages in fields like space exploration and domestic applications considering small space occupation and ease of transport. In the present paper, the influence of resonator diameter on the general performance of a small thermoacoustic Stirling engine was experimentally investigated using helium as the working gas. Reducing the diameter of the resonator appropriately is beneficial for lower onset heating temperature, lower frequency and higher pressure amplitude. Based on the pressure distribution in the small thermoacoustic engine, an outlet for the acoustic work transmission was made to combine the engine and a miniature co-axial pulse tube cooler. The cooling performance of the whole refrigeration system without any moving part was tested. Experimental results showed that further efforts are required to optimize the engine performance and its match with the co-axial pulse tube cooler in order to obtain better cooling performance, compared with its origina...

A new 20 K helium refrigerator installed at NASA Johnson Space Center s Space Environment Simulation Laboratory (SESL) was successfully commissioned and tested in 2012. The refrigerator is used to create a deep space environment within SESL s Chamber A to perform ground testing of the James Webb Space Telescope (JWST). The chamber previously and currently still has helium cryo-pumping panels (CPP) and liquid nitrogen shrouds used to create low earth orbit environments. Now with the new refrigerator and new helium shrouds the chamber can create a deep space environment. The process design, system analysis, specification development, and commissioning oversight were performed by the cryogenics department at Jefferson Lab, while the contracts and system installation was performed by the ESC group at JSC. Commissioning data indicate an inverse coefficient of performance better than 70 W/W for a 18 kW load at 20 K (accounting for liquid nitrogen pre-cooling power) that remains essentially constant down to one third of this load. Even at 10 percent of the maximum capacity, the performance is better than 150 W/W at 20 K. The refrigerator exceeded all design goals and demonstrated the ability to support a wide load range from 10 kW at 15 K to 100 kW at 100 K. The refrigerator is capable of operating at any load temperature from 15 K to ambient with tight temperature stability. The new shroud (36 tons of aluminum) can be cooled from room temperature to 20 K in 24 hours. This paper will outline the process design and commissioning results.

In the framework of the JT-60SA project, a cryogenic loop, dedicated to the tests of the JT-60SA Toroidal Field Coils, is planned to be installed at CEA Saclay. To analyze the dynamic thermal behavior of the cryogenic loop and to optimize the cryogenic process control of the coil test facility, dynamic simulations will be carried out with the software EcosimPro. This paper deals with the validation of the software. Experimental power measurements in pure refrigeration on a helium refrigerator have been compared to computations. Results are close and allow validating the software. The modeling of the JT-60SA CTF cryogenic test loop is also described in order to give an overview of the next computations.

A capillary tube is commonly used in small capacity refrigeration and air-conditioning systems. It is also a preferred expansion device in mixed refrigerant Joule-Thomson (MR J-T) cryocoolers, since it is inexpensive and simple in configuration. However, the flow inside a capillary tube is complex, since flashing process that occurs in case of refrigeration and air-conditioning systems is metastable. A mixture of refrigerants such as nitrogen, methane, ethane, propane and iso-butane expands below its inversion temperature in the capillary tube of MR J-T cryocooler and reaches cryogenic temperature. The mass flow rate of refrigerant mixture circulating through capillary tube depends on the pressure difference across it. There are many empirical correlations which predict pressure drop across the capillary tube. However, they have not been tested for refrigerant mixtures and for operating conditions of the cryocooler. The present paper assesses the existing empirical correlations for predicting overall pressure drop across the capillary tube for the MR J-T cryocooler. The empirical correlations refer to homogeneous as well as separated flow models. Experiments are carried out to measure the overall pressure drop across the capillary tube for the cooler. Three different compositions of refrigerant mixture are used to study the pressure drop variations. The predicted overall pressure drop across the capillary tube is compared with the experimentally obtained value. The predictions obtained using homogeneous model show better match with the experimental results compared to separated flow models.

Superconducting magnets used in tokamaks undergo periodic heat load caused by cycling plasma operations inducing AC losses, neutrons fluxes and eddy currents in magnet structures. In the cryogenic system of JT60-SA tokamak, the Auxiliary Cold Box (ACB) distributes helium from the refrigerator to the cryogenic users and in particular to the superconducting magnets. ACB comprises a saturated helium bath with immersed heat exchangers, extracting heat from independent cooling loops. The supercritical helium flow in each cooling loop is driven by a cold circulator. In order to safely operate the refrigerator during plasma pulses, the interface between the ACB and the refrigerator shall be as stable as possible, with well-balanced bath inlet and outlet mass flows during cycling operation. The solution presented in this paper relies on a combination of regulations to smooth pulsed heat loads and to keep a constant refrigeration power during all the cycle. Two smoothing strategies are presented, both regulating the outlet mass flow of the bath: the first one using the bath as a thermal buffer and the second one storing energy in the loop by varying the cold circulator speed. The bath outlet mass flow is also controlled by an immersed resistive heater which enables a constant evaporation rate in the bath when power coming from the loops is decreasing. The refrigeration power is controlled so that the compensating power remains within an acceptable margin. Experimental validation is achieved using the HELIOS facility. This facility running at CEA Grenoble since 2010 is a scaled down model of the ACB bath and Central Solenoid magnet cooling loop of the JT60-SA tokamak. Test results show performances and robustness of the regulations.

NASA is considering multiple missions involving long-term cryogenic propellant storage in space. Liquid hydrogen and oxygen are the typical cryogens as they provide the highest specific impulse of practical chemical propellants. Storage temperatures are nominally 20 K for liquid hydrogen and 90 K for liquid oxygen. Heat loads greater than 10 W at 20 K are predicted for hydrogen storage. Current space cryocoolers have been developed for sensor cooling with refrigeration capacities less than 1 W at 20 K. In 2011, Creare Inc. demonstrated an ultra-low-capacity turboalternator for use in a turbo-Brayton cryocooler. The turboalternator produced up to 5 W of turbine refrigeration at 20 K; equivalent to approximately 3 W of net cryocooler refrigeration. This turboalternator obtained unprecedented operating speeds and efficiencies at low temperatures benefitting from new rotor design and fabrication techniques, and new bearing fabrication techniques. More recently, Creare applied these design and fabrication techniques to a larger and higher capacity 20 K turboalternator. The turboalternator was tested in a high-capacity, low temperature test facility at Creare and demonstrated up to 42 W of turbine refrigeration at 20 K; equivalent to approximately 30 W of net cryocooler refrigeration. The net turbine efficiency was the highest achieved to date at Creare for a space-borne turboalternator. This demonstration was the first step in the development of a high-capacity turbo-Brayton cryocooler for liquid hydrogen storage. In this paper, we will review the design, development and testing of the turboalternator.

Icing wind-tunnel is the main ground facility for the research of aircraft icing, which is different from normal wind-tunnel for its refrigeration system and spraying system. In stable section of icing wind-tunnel, the original parameters of droplets and air are different, for example, to keep the nozzles from freezing, the droplets are heated while the temperature of air is low. It means that complex mass and heat transfer as well as dynamic interactive force would happen between droplets and air, and the parameters of droplet will acutely change along the passageway. Therefore, the prediction of droplet-air mixed phase flow is necessary in the evaluation of icing researching wind-tunnel. In this paper, a simplified droplet-air mixed phase flow model based on Lagrangian method was built. The variation of temperature, diameter and velocity of droplet, as well as the air flow field, during the flow process were obtained under different condition. With calculating three-dimensional air flow field by FLUENT, the droplet could be traced and the droplet distribution could also be achieved. Furthermore, the patterns about how initial parameters affect the parameters in test section were achieved. The numerical simulation solving the flow and heat and mass transfer characteristics in the mixing process is valuable for the optimization of experimental parameters design and equipment adjustment.