Liquid Nitrogen Consumption Research Articles

The Study and Improvement of Pressure Degradation of Helium Cryogenic System at NSRRC

This paper is aimed at studying and improving the phenomenon of pressure degradation in a helium cryogenic system. There are two 450W helium cryogenic systems for the Taiwan light source (TLS) and one 890W helium cryogenic system for the Taiwan photon source (TPS) housed at the National Synchrotron Radiation Research Center (NSRRC). The TLS helium cryogenic system is used for one superconducting radio frequency (SRF) cavity and five superconducting magnets. The TPS helium cryogenic system is used for two SRF cavities at the present stage. These three helium cryogenic systems have experienced pressure degradation, which reduced their performance and increased liquid nitrogen consumption for precooling over the past few years. A cryogenic adsorber was set up in an effort to capture the impurities, but this made no difference for pressure degradation in the system. The impurities were comprised of not only gas but also moisture. It was found that the cryogenic adsorber was not efficient enough to remove the moisture. This paper presents the study for the phenomena of pressure degradation. A moisture removal system was designed which is also discussed.

On the chip formation mechanism when cutting Ti6Al4V with localised supply of liquid nitrogen

In cryogenic machining, employing internal supply cooling through the tool not only diminishes tool wear and enhances workpiece machining quality but also offers the benefits of reduced liquid nitrogen consumption and more precise cooling. These advantages are particularly noteworthy for efficiently machining challenging materials. However, prevailing research on internal supply cooling through tools predominantly concentrates on aspects such as tool wear and surface integrity, with a relatively limited exploration of material removal mechanisms. The material removal process stands as a crucial factor influencing cutting stability and surface smoothness. Thus, this study focuses on the Ti-6Al-4 V alloy, utilizing numerical modeling to investigate the impact of liquid nitrogen cooling methods on the cutting deformation zone. In addition to its benefits for difficult-to-machine materials, internal supply cooling through the tool presents a promising avenue to enhance machining efficiency. Consequently, this study strategically selected the Ti-6Al-4 V alloy as the research subject, employing numerical modeling to delve into the influence of liquid-nitrogen cooling methods on the cutting deformation zone. Furthermore, employing a combination of cutting experiments and simulations, we analyzed the evolution of temperature fields and microstructures within the deformation zone to elucidate the chip formation mechanism under liquid nitrogen cooling conditions. The outcomes of this investigation reveal that in comparison to liquid nitrogen external supply cooling, internal supply cooling through the tool effectively restrains chip serration, thereby contributing to an enhancement in machining quality. The analysis demonstrates that, under conditions of internal supply cooling through the tool, chip formation is predominantly influenced by the adiabatic shear effect induced by low temperatures. In contrast, under external supply cooling conditions, susceptible to the low-temperature embrittlement effect, the chip's free surface tends to undergo brittle cracking. This shift in the chip formation mechanism toward the co-dominance of adiabatic shear and brittle cracking results in a more pronounced serration of the chips. This study establishes a theoretical foundation and guides the industrial application of cryogenic machining.

Numerical simulation of ice plugging process using multi-jacket method in nuclear power pipes

Introduction: Ice plugs acts as isolate maintenance sections during pipeline repairs in nuclear power plants can effectively reduce maintenance costs, which is formed by the cooling of liquid nitrogen. The single-jacket freezing method takes a long time for the formation of ice plugs with a certain load-bearing capacity, increasing the liquid nitrogen consumption.Methods: In this study, a multiple-jacket method for the formation of ice plugs was proposed, and the numerical simulation using CFD (Computational Fluid Dynamics) was conducted. The effects of total jacket length and jacket number on freezing time and the consumption of liquid nitrogen were analyzed.Results and Discussion: Research indicated that the multiple-jacket method obtained a 11%∼15% decrease in freezing time and a 18%∼26% decrease in liquid nitrogen consumption than the single-jacket method. For the multiple-jacket method, the gap between the jackets presented a certain influence on the freezing time and liquid nitrogen consumption. As the gap between the jackets increases, there exist a small increase in the freezing time, but the liquid nitrogen consumption will be reduced by 2% to 5%.

Preliminary evaluation of NEG materials in view of CMSB replacement in HCPB TER architecture

CMSB (Cryogenic Molecular Sieve Beds) operated at 77 K is used for tritium recovery in the reference design of HCPB (Helium Cooled Pebble Bed) TER (Tritium Extraction and Removal) system. However, this technology has two main drawbacks: large consumption of liquid nitrogen and the controlling of tritium stream sent to the Tritium Plant, during the regeneration of the CMSB, in such way to avoid large variations in the gas flow rate.This paper reports on a preliminary evaluation for CMSB replacement by non-evaporable getter materials for tritium recovery. The advantages of NEG technology are the high specific pumping speed and capacity and the ability to withstand a large number of absorption/desorption cycles. In addition, NEG do not release hydrogen unless power is supplied to heat them, addressing an important safety issue related to uncontrolled release in case of power outage or subsystem failures.

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For the preservation of horticultural products, the best results in keeping the attributes and quality at a level as close as possible to that of the fresh product are obtained when artificial cold (refrigeration, freezing) is used, unlike other methods. Among the existing freezing methods, freezing with cryogenic agents allows obtaining average linear freezing rates superior to the other methods. The fastest procedure for cooling food products involves the use of liquid nitrogen, which comes into direct contact with the surface of the food product that needs to be frozen. The paper analyzes the quick freezing process of three species of berries, namely blueberries, strawberries and raspberries, using an experimental model of multifunctional quick-freezing equipment - ICR, developed by INMA Bucharest as part of a national research programme. Total times and average linear freezing rates, as well as liquid nitrogen consumptions for each of the three species subjected to freezing, were tracked. Following the analysis of the experimental data, there were found the following: the minimum total freezing time, 498 s, was recorded for blueberries and the maximum total freezing time, 773 s, was recorded for strawberries; for blueberries and strawberries the average linear freezing rates recorded values of 6.32 cm/h and 6.29 cm/h corresponding to a very fast freezing process and for raspberries the average linear freezing rate recorded a value of 1.62 cm/h corresponding to a fast freezing process; liquid nitrogen consumption recorded a minimum value of 6.90 kg for blueberries and a maximum value of 7.20 kg for raspberries. In the case of blueberries, at the end of the freezing process, cracks and fissures of the epidermis and pulp were observed as a result of the thermal shock induced during the very rapid freezing process.

Temperature transition optimization in cryogenic systems: Application to liquid nitrogen expenditure reduction in a thermal vacuum chamber case study

This paper presents outcomes regarding liquid nitrogen consumption reduction in a thermal vacuum chamber, with the motivation of lessening operational costs during space equipment testing. The article briefly outlines the optimal control application to thermal and cryogenic-related control systems based on a gas cycle, and assesses liquid nitrogen savings opportunities for a chamber including six shrouds with independent temperature requirements. In this case study, optimization of temperature transition profiles and a proposed modification in the control setup yielded potential savings from 14.1% to 20.4% in the examined experimental transitions.

Conceptual Design of Scanning Magnets Using HTS Coils Wound With Spiral Copper-Plated Striated Coated-Conductor (SCSC) Cables for Carbon-ion Radiotherapy

When we reduce the size of a rotating gantry using high field superconducting bending magnets, we must also increase the magnetic field of scanning magnets. We conceptually designed scanning magnets using HTS coils wound with Spiral Copper-plated Striated Coated-conductor (SCSC) cable, which is a low-ac-loss, high current cable concept. The coils were designed to cooled at 65 K by using liquid nitrogen. We conducted the two-dimensional cross-sectional design of the HTS coils as well as warm iron yokes by finite element magnetic field analysis. AC losses in the HTS coils and iron losses in the yokes were calculated. Electrical power consumption to excite the magnets, liquid nitrogen consumption to cool the HTS coils, and the terminal voltages of the magnets were calculated to discuss the feasibility of the designed scanning magnets.

Tunable Spatial Resolution of a Scanning Probe Microscopy (SPM) by an Efficient Cryosorption Pump

Scanning Probe Microscopy (SPM) is a useful instrument to study the surface topography of the sample at an atomic resolution. SPM system is sensitive to vibration and contamination on the surface, and therefore a vibration-free and clean environment are required to improve spatial resolution in Z-height. In this paper, a detailed new design of stand alone cost effective, vibration free activated carbon based cryosorption pump integrated and its detailed integration with SPM system is discussed. The efficiency of cryosorption pump depends on the radial temperature distribution, which was analysed using transient thermal analysis in Ansys software. The temperature profile obtained from the thermal simulation results reveals that a spiral wound copper mesh based partition surrounding the activated carbon in cryosorption pump improves the temperature distribution in the radial direction. The pump can operate with a maximum of 25 litres of Liquid nitrogen consumption and 4.5 hrs of continuous operation. The activated carbon was used as an adsorbent showed a hexagonal crystal structure from the X-Ray Diffraction (XRD) studies and its average pore size was obtained from by Brunauer-Emmett-Teller (BET) analysis was 0.34 nm. These tests were conducted to determine the effect on the pump-down characteristics of developed cryosorption pump. The improvement in spatial resolution was studied through detailed experimental analysis in Conductive Atomic Force Mode (CAFM) by Piezo Force Microscopy (PFM) which showed a 50 percent decrease of the current when imaged in a vacuum environment, phase and magnitude images showed the less distorted and clear visibility of the piezo domains. The magnetic interaction by Magnetic Force Microscopy (MFM) Q-factor was studied at the resonance frequency of 61.5 kHz. MFM showed that the Q-factor improved from 20 to 500 at 1E-3 mbar operating pressure. The drift of the MFM tip with respect to holding time showed a saturated Q-factor at 500. Non-contact mode by Atomic Force Microscopy (AFM) showed a spatial resolution enhancement of 0.89 nm.

Numerical and Experimental Analysis of the ZFC Heat Release from a YBCO Bulk and Validation of YBCO Thermal Parameters

This article presents results from a simple experimental methodology used to determine the amount of heat transferred from an yttrium barium copper oxide (YBCO) bulk to liquid nitrogen (LN2) and LN2 consumption during the process of zero-field cooling (ZFC). The thermal power can be determined from the YBCO bulk temperature variation, which is difficult to measure with accuracy. In this procedure, the thermal power from the YBCO bulk to LN2 is determined from the measured rate of LN2 evaporation, considering the LN2 latent heat. To reduce the influence of room temperature heating and make the LN2 mass variation depend as much as possible on the heat released from the YBCO bulk, a step transient from room temperature into the LN2 is performed. The precision of results is determined from the rate of LN2 evaporation due to room temperature heating with the bulk already cooled by ZFC. The temperature evolution at the bulk lateral surface where the heat transfer is higher is also measured. The results from experimental measurements are compared with 3D finite element analysis (FEA) numerical results. The obtained evolutions of the temperature and thermal power from the YBCO bulk are used to validate YBCO thermal parameters, such as thermal conductivity and specific heat capacity at constant pressure. The YBCO bulk equivalent heat capacity and thermal resistance are determined by analyzing the equivalent first-order thermal lumped parameter circuit based on the obtained evolutions in time of the YBCO temperature and heat transferred to the LN2. The characteristics of dependence of the YBCO thermal resistance and heat capacity with temperature are obtained by correlating their time evolutions with the bulk average temperature evolution in time. The YBCO-specific heat capacity at constant pressure is then calculated by dividing the obtained bulk heat capacity by the bulk mass. The YBCO thermal conductivity is calculated from the obtained thermal resistance considering an equivalent bulk section and length toward the main direction of heat flux.

The performance regulation optimization and engineering application of a domestic helium liquefier

<p indent="0mm">The superconducting magnets and the superconducting cavities are the key devices of large-scale scientific facilities, such as the HL-LHC in the CERN, the ITER, the EAST, the CiADS, and so on. A stable and reliable cold source such as the liquid helium (–269°C) is required to keep the superconducting magnets and the superconducting cavities working. Therefore, a helium liquefier or a helium refrigerator working at <sc>4.5 K</sc> is necessary for them. Research on high-field-strength superconducting dipole magnets used in future high-energy particle colliders is developed in the Institute of High Energy Physics of the Chinese Academy of Sciences. High-field-strength superconducting dipole magnets have large thermal loads and long test durations, which need large amount of liquid helium for their performance tests. Therefore, the long-term operating economy, stability, and reliability of the refrigeration system are highly required. The engineering application of using a helium liquefier for producing liquid helium to cool down superconducting dipole magnets has not been realized in China yet. Meanwhile, the price of the imported helium liquefiers is usually too high and the supply cycles are too long. Fortunately, a domestic helium liquefier has been developed by the Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences. This paper will realize the engineering application of the domestic helium liquefier applied to the superconducting dipole magnet test platform for the first time. In order to meet the test requirements of high-field-strength superconducting dipole magnets, a performance regulation and optimization of the first domestic helium liquefier is studied. It realizes the optimal control of the cold-box cooling process and the Dewar cooling process, saves the power consumption of the compressor by 12.3% and 25.2% respectively, and significantly improves the economy of the helium liquefier. After the commissioning of the liquefier, the helium liquefier realizes the automatic control adjustment function to adapt to variable loads in different operating conditions. And the specific energy consumption of the helium liquefier under each load state is analyzed. Without considering the consumption of liquid nitrogen, the minimum specific energy consumption of the helium liquefier is <sc>2.4 kW h/L</sc> when the liquefier works with the full load. Through control optimization and experimental testing, the helium liquefier successfully realizes the joint operation with the user-end superconducting dipole magnet test platform, and passed the long-term operation reliability test. At present, the helium liquefier has run stably for more than two months, produced more than <sc>35000 L</sc> of liquid helium, promoting the first domestic accelerator high-field superconducting dipole magnet to achieve a breakthrough in the new index of the magnetic field strength of <sc>12.47 T.</sc> It’s the first time for the domestic helium liquefier applying to the superconducting dipole magnet test platform, and this engineering application can be further promoted in future.

Experimental investigation of cryogenic flow quenching of horizontal stainless steel tubes

Cryogenic fluid is frequently used in such fields as cryogenic cooling, food engineering and chemical process, etc. It has been understood in pool quenching experiments that a thin low-thermal-conductive coating layer on the wall can greatly improve the cooling performance, while less is known about the flow quenching. In the present study, the experiments are conducted to investigate cryogenic flow quenching of the horizontal stainless steel tubes with the Teflon coating layers on the inner wall. To explore the influence of the coating layer on the quenching performance, three Teflon coating layers of distinct thicknesses are fabricated on the inner wall of the stainless steel tubes, and the quenching efficiency and quenching heat transfer performance are compared with those of the bare tube. It is shown that the thin coating layer on the inner tube wall can significantly shorten quenching time and reduce the consumption of liquid nitrogen at different inlet pressures. The quenching time of the Teflon-coated tube is reduced by up to about 78.5%, and the maximum quenching efficiency of the Teflon-coated tube is above 50.0% compared with 8.0% of the bare tube. The improvement of quenching performance in the present study is ascribed to the fact that the sharp temperature drop of the Teflon coating layer surface upon cooled by liquid nitrogen makes the transition boiling with higher heat transfer coefficient replace film boiling at a higher average wall temperature, leading to a reduction in quenching time and an improvement in quenching efficiency.

Analysis and optimization of cooling channels performances for industrial extrusion dies

Liquid nitrogen cooling is widely used in the extrusion industrial practice in order to increase the production rate, to reduce the die temperature and to avoid defects on the profile exit surfaces resulting from an excessive heating. However, the efficiency of the cooling is deeply affected by position and design of the liquid nitrogen channel so that numerical modelling is gaining an increasing industrial interest in relation to the possibility offered to optimize the channel design without expensive and time-consuming experimental trials. In this work, a numerical FE model developed within COMSOL Multiphysics® is proposed and validated against experimental trials performed in industrial environment. The model combines the 3D simulation of the extrusion process with a 1D model of the cooling channel thus allowing the testing of a number of different solutions at the die design stage. The global aim of this work is the assessment of the liquid nitrogen cooling efficiency in the extrusion of an industrial aluminum profile and the proof of the potentials offered by numerical models to get an optimized channel design in terms of cooling efficiency, die thermal balancing and reduction of liquid nitrogen consumption.

Thermo-Hydraulic Analysis of a Horizontal HTS ZFC Levitating Bearing Concerning Its Autonomy Safety Service Time

Electromagnetic heating of high-temperature superconductors (HTSs) and non-perfect thermal insulation of cryostats cause liquid nitrogen (LN2) vaporization and consumption. This paper presents results from the thermo-hydraulic analysis of the maximum safety service time of the prototype of a horizontal axis radial levitation bearing with zero-field cooled (ZFC) HTS bulks. It first studies the temperature sensitivity of yttrium barium copper oxide (YBCO) bulks to the LN2 level, particularly when partially immersed. This, when the main component of heat flux is according to the c-axis of the bulk crystal structure, that is the case of the studied bearing prototype and in most of all cryostats of maglev vehicles. Measurements used two platinum resistance thermometers leaning the top and side surfaces of a non-magnetized ZFC YBCO bulk. Correlations between the temperatures measured by the two platinum resistors are made to determine the average temperature of YBCO bulk. The thermal-time constant associated with a YBCO bulk losing contact with LN2 is also determined for two conditions: 1) initial ZFC and 2) initial field-cooled (FC) under the influence of typical magnetic field values generated by the studied bearing permanent magnet (PM) rotor. Results indicate that the YBCO temperature evolution is not notably affected by Joule losses from initial magnetization currents for this bearing. Due to continuous PM rings, the magnetic field perceived by the YBCO bulks does not change in the ideal case of spinning with no vibrations. Another experiment shows that the heating by induction from vibration dynamics does not contribute notably to LN2 consumption. Finally, the safety service time is verified from measured LN2 mass and level evolution in the HTS bearing's stator, due mainly to defective thermal insulation from the room temperature. The process consisted of calculating the times that different leveled YBCO bulks experiments reached the critical temperature and using the conclusions taken from the initial study about the temperature sensitivity of single bulks to the LN2 level. 3D finite element simulations reinforce our experimental results.

System design and experimental verification of an internal insulation panel system for large-scale cryogenic wind tunnel

With the rapid development of aerodynamics for high speed aircraft, the flight experiments need to be carried out under ultra-high Reynolds number condition to simulate actual high-speed flight conditions, which puts forward higher requirements for the wind tunnel. Reynolds number increases rapidly as the decrease of the flow temperature because the viscosity of the working gas decreases and the density increases. As a result, a pressurized tunnel at cryogenic temperature can provide real-flight Reynolds numbers. Therefore, cryogenic wind tunnel is one of the best testing facilities to rech ultra-high Reynolds number. The thermal insulation system is crucial for the design and operation of the cryogenic wind tunnel. In this paper, the features of an internal insulation system for the cryogenic wind tunnel are firstly highlighted in comparison with traditional insulation systems. The internal thermal insulation system for the cryogenic wind tunnel is discussed. In order to evaluate the thermal insulation performance, the heat transfer calculation for a typical wind tunnel region with the diameter of two meters is carried out using finite element method based on the analyses of the heat transfer conditions. The averaged heat load from the environment is obtained to optimize the liquid nitrogen consumption during the wind tunnel operation. The thickness of the panel should be 150 mm to reach the design target of averaged heat flux 60 W/m2. Meanwhile, the typical region is constructed according to the new internal insulation system. Cryogenic test is conducted and it is proven that the new internal insulation system could efficiently prevent the environment heat flow and ensure the normal operation of the cryogenic wind tunnel.

Optimization of a novel cryogenic air separation process based on cold energy recovery of LNG with exergoeconomic analysis

Oxyfuel combustion is deemed as one of the most potential technology to reduce CO2 emission from power plant. Exploring the technology of low-cost high-purity oxygen is a key issue to the implement of oxyfuel combustion. Cryogenic air separation is routinely used in large-scale production of high-purity oxygen. However, the relatively high power consumption of traditional cryogenic air separation no longer satisfies the requirement for cost-effective high-purity oxygen generation in the industrial field. A novel three-column cryogenic air separation process integrated with liquefied natural gas (LNG) regasification is introduced and evaluated in this paper. Waste nitrogen full utilization, cascade heat transfer and multi-column air distillation strategies are employed. To confirm the rationality and validity of the process, pinch point, energetic, exergetic and exergoeconomic analyses are performed. The obtained results indicate that the specific power consumption of liquid oxygen and liquid nitrogen are 0.252 kWh·kg-1 and 0.258 kWh·kg-1 in the proposed integrated system. The overall exergy efficiency and the LNG cold exergy utilization efficiency reach 0.7165 and 0.5318, respectively. Furthermore, sensitivity analysis is employed to investigate the effects of the outlet temperature of sub-coolers and stage number of low pressure column on total power consumption and equipment investment of the proposed process.

Анализ эффективности охлаждения углеводородного топлива с использованием жидкого азота и комбинации рекуперативных теплообменников

The paper describes the propellant cooling system using liquid nitrogen and a combination of recuperative heat exchangers, including sections of the double pipe heat exchanger and a twisted heat exchanger located in a tank with antifreeze, cooled by nitrogen gas coming out of the sections of the double pipe heat exchanger. Mathematical models of cooling processes for two variants of movement of propellant and liquid nitrogen in the channels of the double pipe heat exchanger sections are considered. Their using makes it possible to analyze the efficiency of propellant cooling operations depending on its mass, design parameters of the system tanks and heat exchangers, consumption characteristics of nitrogen and propellant, as well as to predict the required mass of liquid nitrogen and the time of propellant cooling during the operation of launching complex propellant-feed systems. Calculated dependences and simulation results of propellant and antifreeze cooling in a tank with a twisted heat exchanger are presented. The influence of variants of arranging propellant cooling processes and liquid nitrogen consumption on the efficiency of the cooling system is analyzed. Comparing to the available systems the capability of reducing the cost of liquid nitrogen are identified as well as reducing time of the propellant cooling operations by means of equipping launch complexes.

Design of the DUNE APATF cryogenic system

Fermi National Accelerator Laboratory (FNAL) is developing the international Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) to advance neutrino science. The flagship of the DUNE project consists of a large particle detector constructed one-mile (1.6 km) beneath the surface at the Sanford Underground Research Facility (SURF) in Lead, SD. The SURF detector is the largest of its type ever built and is comprised of four cryostats totaling 70,000 tons of liquid argon (LAr) to record neutrino interactions with unprecedented precision. Each cryostat houses a detector, the first includes 150 Anode Panel Assemblies (APA) submersed within 17,500 tons of LAr. Before installing 150 APA within the SURF detector they will be cryogenically cooled to nominally 90 K at the APA Test Facility (APATF) utilizing nitrogen flows. The APATF cryogenic system is entirely located one-mile underground at the SURF facility and includes nominally 13 kW of refrigeration at 80 K, cryogenic transfer lines, APA test cryostats, a cryogenic control system, and various control and pressure safety elements to ensure performance and safety requirements are achieved. The APATF preliminary design is in progress and major considerations include an efficient, cost-effective mechanism to deliver the required refrigeration to the APATF underground, support of rigid testing intervals to support the DUNE operating schedule, temperature stability of the APA and electronics within cryostats, efficient cryogenic system operation to minimize heat leak and/or liquid nitrogen consumption, thermo-mechanical stability and flexibility of components, and pressure safety of the APATF cryogenic system. Installation and integration of the APATF cryogenic system within the footprint and to adjacent sub-systems is also discussed.

Relative acoustic gas thermometry setup for low temperature range from 4,2 to 80 K

Relative acoustic gas thermometry setup is described. Described setup was developed and tested in VNIIFTRI. The setup is designed for the measurement of thermodynamic temperature in low temperature range down to 4,2 K. Main part of the setup is resonator with reduced cavity diameter. Reduction of resonator dimension lead to several times reduction of cooled parts of the setup with respect to the setup previously developed in VNIIFTRI. This decreases liquid nitrogen and liquid helium consumption required for cooling of resonator. Moreover, reduction of the mass of cooling parts reduces time required for temperature stabilization and thus measurement time. In the work the tests’ results of operation of main parts of the setup are presented.

Reducing operational costs of thermal vacuum testing of spacecraft via gaseous nitrogen thermal conditioning technology

Many new thermal vacuum testing programs for ground testing of spacecraft require ensuring high accuracy temperature regime in a wide temperature range. Thermal vacuum tests are notable for significant material costs. Therefore, the requirement to reduce operating costs, including those associated with ensuring the temperature regime, is not less relevant. This explains the increased interest in promising energy-efficient technologies, one of which is based on the thermal conditioning of gaseous nitrogen. Systems with gaseous nitrogen thermal conditioning units have an optimal combination of operational and technical characteristics and, compared to systems where liquid nitrogen is poured into cryogenic screens, have lower consumption of liquid nitrogen and electrical energy, especially in stabilized temperature regime. The risk of contamination of the thermal vacuum chamber and the test object due to leaks of the liquid coolant is eliminated. Due to the fact that the properties of nitrogen quite accurately correspond to the ideal gas law, modeling of such systems is relatively simple, and the characteristics are predictable and stable. The article provides a brief analysis of the characteristics of gaseous nitrogen thermal conditioning units of two leading foreign manufacturers and the results of the practical application of four foreign manufactured thermal conditioning units with different characteristics in a typical thermal vacuum chamber. We considered the main directions of improving the characteristics of thermal conditioning units by foreign manufacturers. The conclusion is made about the high efficiency and economic feasibility of gaseous nitrogen thermal conditioning technology in most cases of thermal vacuum testing.

Design and Test of Cryogenic Cold Plate for Thermal-Vacuum Testing of Space Components

This paper proposes a novel cryogenic fluid cold plate designed for the testing of cryogenic space components. The cold plate is able to achieve cryogenic temperature operation down to −196 °C with a low liquid nitrogen (LN2) consumption. A good tradeoff between high rigidity and low thermal conduction is achieved thanks to a hexapod configuration, which is formed by six hinge–axle–hole articulations in which each linking rod bears only axial loads. Thus, there is not any stress concentration, which reduces the diameter of rod sections and reduces the rods’ thermal conduction. This novel design has a unique set of the following properties: Simple construction, low thermal conduction, high thermal inertia, lack of vibrational noise when cooling, isostatic structural behavior, high natural frequency response, adjustable position, vacuum-suitability, reliability, and non-magnetic. Additionally, the presented cold plate design is low-cost and can be easily replicated. Experimental tests showed that a temperature of at least −190 °C can be reached on the top surface of the cold plate with an LN2 consumption of 10 liters and a minimum vibration frequency of 115 Hz, which is high enough for most vibration tests of space components.