Cryogenic Liquid Research Articles

Conceptual design and performance evaluation of a novel cryogenic integrated process for extraction of neon and production of liquid hydrogen

Novel integration of a hydrogen liquefaction process and cryogenic rectification of air is presented. The thermodynamics analysis including the 2nd Law and sensitivity analysis regarding this process are conducted. The proposed cryogenic process can produce 111.3 kg/s of nitrogen and 42 kg/s of oxygen with argon. In addition, this process produces more than 132 × 103 tons of liquid hydrogen and 751 tons of crude neon per year. Moreover, as the number of the used compressor is very fewer than of the conventional process, the required power consumption of the proposed cryogenic plant is almost low. Based on the exergy analysis, using expanders, providing the requested refrigeration condition by solar heat exchangers and proper streams, and integrating two processes with the similar operating condition, the exergetic efficiency of the cycle is more than 70 %. The sensitivity analysis of operating parameters such as pressure, temperature, reflux ratio, and the number of stages of column presents their the importance of them on the recovered neon, oxygen, and nitrogen. Moreover, the production of cryogenic liquids is more sensitive to operating pressure and temperature than the reflux ratio and the number of stages.

Magnetic, Mechanical and Thermal Modeling of Superconducting, Whole-body, Actively Shielded, 3 T MRI Magnets Wound Using MgB2 Strands for Liquid Cryogen Free Operation.

we present magnetic, mechanical and thermal modeling results for a 3 Tesla actively shielded whole body MRI (Magnetic Resonance Imaging) magnet consisting of coils with a square cross section of their windings. The magnet design was a segmented coil type optimized to minimize conductor length while hitting the standard field quality and DSV (Diameter of Spherical Volume) specifications as well as a standard, compact size 3 T system. It had an overall magnet length and conductor length which can lead to conduction cooled designs comparable to NbTi helium bath cooled 3 T MRI magnets. The design had a magnetic field homogeneity better than 10 ppm (part-per-million) within a DSV (Diameter of Spherical Volume) of 48 cm and the total magnet winding length of 1.37 m. A new class of MgB2 strand especially designed for MRI applications was considered as a possible candidate for winding such magnets. This work represents the first magnetic, mechanical and thermal design for a whole-body 3 T MgB2 short (1.37 m length) MRI magnet based on the performance parameters of existing MgB2 wire. 3 Tesla MRI magnet can operate at 20 K at 67 % of its critical current.

Optimum coating thickness for the fastest chilldown of Teflon-coated stainless steel flat plate in liquid nitrogen pool

In this study, a novel model was developed to accurately determine the optimum thickness of a low-thermal-conductivity coating layer applied on a stainless steel flat plate resulting in the fastest chilldown of the plate in a cryogenic liquid pool. A low-thermal-conductivity layer coated on a metal surface is known to significantly reduce the cryogenic chilldown time of the metal by facilitating the early transition from film to nucleate boiling. However, there is still a lack of models to estimate the optimum coating thickness. An attempt has been made to address this issue. To do so, the authors first investigated the transient pool boiling of liquid nitrogen on Teflon-coated stainless-steel plates with various coating thicknesses ranging from 0 to 300 μm. Both the pool mass and plate temperature over time were measured and used to determine the heat flux into the liquid pool. A coating layer that results in a lower thermal resistance during film boiling would lead to a higher thermal resistance in nucleate boiling. As the thickness of the coating layer increases, the thermal resistance in film boiling decreases and the transition from film to nucleate boiling occurs earlier. The early transition of the boiling regimes was successfully explained by the assumption of intermittent liquid-solid contact during the film-boiling regime. The coating thickness in the range of 100–150 μm was observed to be the optimum thickness that resulted in both the smallest thermal resistance and earliest transition of boiling regimes. Subsequently, a new model to estimate the optimum coating thickness was derived based on experimental observations and the assumption of intermittent liquid-solid contact. The findings of this study are expected to be beneficial in enhancing the chilldown efficiency of cryogenic systems.

Numerical Study of Effect of Pressurant Gas Species on Thermal Behavior in Cryogenic Tank

This study numerically reveals effect of pressurant gas species on thermal behavior in a cryogenic propellant tank for space propulsion systems. The simulation was conducted for a ground experiment using liquid nitrogen in which gaseous helium and the same species as the liquid, gaseous nitrogen, were used as prepressurants. The tank was sealed after prepressurization to observe self-pressurization (pressure rise with evaporation) and thermal stratification (high-temperature liquid near the surface). A higher evaporation rate and a thicker thermal layer were observed for helium prepressurization in the experiment. To clarify the underlying physics, a simulation considering phase change and conjugate heat transfer was developed. The simulated pressure and temperature closely matched the experimental results. Conjugate heat transfer played an important role; that is, the heat flow through the ullage part of the tank skin into the cryogenic liquid was a dominant heat transfer process, causing evaporation to occur mainly at the contact point of the wall and the gas–liquid interface. Afterward, nitrogen vapor rose along the tank wall due to buoyancy under nitrogen prepressurization. However, buoyancy in the ullage is lower under helium prepressurization since light helium stayed in the upper part of the ullage, and a radial vapor flow is produced from the contact point, leading to a higher heat flux from the tank wall to the liquid nitrogen. This mechanism shows that evaporation rate and heat flow into the liquid are higher for helium prepressurization than for nitrogen prepressurization.

The effect of external heat inflow to the cryogenic liquid pressurized discharge process

The launch vehicle with a liquid propulsion system requires pressurization during the propellant discharge. While the launch vehicle is flying through the air layer, a process in which frictional heat is generated between the liquid propellant tank and the air layer can be assumed. External heat inflow occurs during the liquid discharging process, and it is necessary to investigate how the external heat influx affects the liquid pressurized discharge process. A test device was constructed to determine the effect of pressurization of external heat inflow. The test device consisted of a liquid tank located in a vacuum chamber and a heating device to simulate external heat inflow. The heating device is a halogen lamp. The cryogenic liquid discharge with and without external heat inflow was compared. It was confirmed that the amount of pressurant gas used was decreased when there was external heat inflow. External heat inflow contributes to the evaporation of the liquid, and the evaporated gas increases the pressure of the ullage.

Cryogenic test bench for the experimental investigation of cryogenic injection in rocket combusters under high-altitude conditions

Due to current and future environmental and safety issues in space propulsion, typical propellants for upper stage or satellite rocket engines such as the toxic hydrazine are going to be replaced by green propellants like the combination of liquid oxygen and hydrogen or methane. The injection of that kind of cryogenic fluid into the vacuum atmosphere of space leads to a superheated state, which results in a sudden and eruptive atomization due to flash boiling. For a detailed experimental investigation of superheated cryogenic fluids the new cryogenic test bench M3.3 with a temperature controlled injection system at high-altitude conditions was built at DLR Lampoldshausen. First run-in tests as well as several measurement campaigns with liquid nitrogen as the test fluid showed the performance and suitability of the new test bench for the systematical investigation of cryogenic flash boiling. Besides new insights into the flash boiling process of cryogenic liquids, the experimental data of cryogenic flash boiling generated with this test bench provide a comprehensive database for the validation of numerical models and further numerical investigations.

The experimental measurement of the thermal emissivity of a black coating from 50 K to 300 K

High-emissivity coatings are commonly applied in satellite detectors and large-scale cryogenic systems. Accurate and quick measurement of emissivity is in high demand for practical applications at cryogenic temperatures. In this paper, a method for the measurement of the total hemispherical emissivity from 50 K to 300 K was presented based on the static calorimetric method. A two-stage GM cryocooler was used as a cooling source in the measuring device without assumption of cryogenic liquids. The thermal emissivity of a black carbon coating was measured by monitoring temperatures timely in the device. The tested results exhibited good accordance with previous reports. This cryogenic measurement device has made it a strong candidate for the radiative heat dissipation at cryogenic temperatures. Design details of the experiment and measurement results will be presented.

Liquid nitrogen removal of lunar regolith simulant from spacesuit simulants

Lunar dust is a major concern for future missions to the Moon. The small size, abrasiveness, sharp morphology, toxicity, and pervasive nature of the dust can cause significant distress to both human health and equipment. Traditional spacesuit cleaning methods such as brushing and vacuuming have limited effectiveness and pose risks such as suit fabric abrasion and seal contamination. A novel mitigation method is to harness the properties of cryogenic liquids. As the liquid rapidly boils, insulated droplets form that lift and carry the dust away from the suit material, migrating toward the lowest point in an airlock for convenient collection. This publication discusses initial testing of the concept for removing lunar regolith simulant from spacesuit simulants with liquid nitrogen. A cryogen sprayer technology was adapted to investigate the effect of angle, application distance, and application time on the efficacy of dust removal. Methodology and uncertainty are presented to determine a removal percent by mass. Preliminary results show mass removal of simulated lunar dust from simulated spacesuit fabric to be greater than 90% for particles less than 10 microns. Estimated calculations are presented to demonstrate the suitability for using the concept to efficiently clean spacesuits and for the ancillary purpose of pressurizing an airlock.

Analysis of oxygen liquefaction with transient flow rates for ISRU systems

Human occupation of lunar and Martian surfaces requires in-situ resource utilization (ISRU) to create a sustainable environment with the limited resources available in space. Fuel and oxidizer generation is essential for developing a refuelling capability for spacecraft, significantly reducing the propellant mass required for landing. Liquefaction systems are a key step in producing and storing cryogenic liquids such as oxygen, hydrogen, and methane. All those fluids are critical to propulsion, life support, and other spacecraft systems. NASA has previously confirmed the presence of water on the Moon and an electrolysis process can be used to separate the oxygen from the hydrogen molecules. Oxygen has also been found within lunar regolith and can be separated through ISRU processes. The extracted oxygen gas can then be liquefied inside a storage tank with tube-on-tank heat exchangers for future use as an oxidizer for propellants. While steady state liquefaction performance is easy to model, power limitations and cyclical environments caused by the change in Sun exposure between day and night periods potentially call for transient operations. The following analysis was performed using the Thermal Desktop software to investigate how various transient gaseous oxygen (GOX) flow rates impact the production and storage of liquid oxygen (LOX) in a 1-g liquefaction system. Variations of sinusoidal and exponential step functions were selected to model potential GOX flow rates that could be experienced by ISRU systems on lunar or Martian surfaces. This early computational analysis provides some insight on how transient operations impact oxygen liquefaction systems and helps illustrate operational questions to explore experimentally throughout the design process.

Investigation on the dynamic adsorption characteristics of activated carbon to Helium-4 for 4-20 K regenerator of cryocoolers

With the advantages of long life and high reliability, cryocoolers gradually substitute cryogenic liquids to become a critical guarantee for the stable operation in space exploration. For cryocoolers, the regenerator is a key component that strongly influences its refrigeration performance. The specific heat of current commonly-used regenerator materials below 20 K is significantly lower than that of the working gas Helium-4, resulting in insufficient cold storage capacity of the regenerator and further limiting the cryocooler’s ability to obtain lower temperatures and larger cooling capacity. In this paper, activated carbon is used to absorb a part of helium in the regenerator to replace the traditional magnetic regenerator materials. By establishing a low-temperature dynamic adsorption model, the dynamic adsorption characteristics of activated carbon to Helium-4 in the temperature range of 4-20 K were studied, and the effect of its microscopic adsorption/desorption heat effect on the performance of the regenerator was investigated.

Dynamic modeling and analysis of bunkering and pressurization for marine LNG fuel tank

Liquefied natural gas (LNG) is becoming an ideal alternative fuel for vessels because of its environmental and economic advantages. As LNG is a cryogenic fuel stored around -163 °C, the LNG fuel tank is a highly non-equilibrium thermodynamic system especially during bunkering and pressurization processes. The accurate prediction of the thermodynamic behaviors inside the LNG fuel tank is critical for the system design and operation. In this study, a fast and effective analytical model of bunkering and pressurization for marine LNG fuel tank was developed. The Norwegian car ferry MF Korsfjord was chosen as a benchmark case to confirm the validity of the model. The top spray filling process, the pressurization process, and the fuel gas supply process of the MF Korsfjord were simulated. The model prediction showed good agreement with the measured data. Besides, cryogenic liquid sloshing inside the fuel tank was investigated as well. The results showed that the sloshing had a severe impact on the tank pressure, especially when the resonance condition of the tank was met, resulting in the shutdown of gas engines in extreme situations.

Influence of cooling temperature on load-carrying performance of a radial HTS magnetic bearing

High temperature superconducting (HTS) magnetic bearing can operate in the harsh environment of low temperature and negative pressure with low loss and self-stability. Therefore, it has been gradually applied in flywheel energy storage, cryogenic liquid pump, cold compressor and some other cryogenic rotating machinery. The load-carrying performance of HTS magnetic bearing is affected by the cooling temperature of HTS directly. In this paper, the linear model is used to modify the temperature dependence to evaluate the influence of cooling temperature on load-carrying performance quantitatively, and the results are analyzed and displayed from the aspects of maximum levitation force, levitation stiffness and hysteresis effect. The research results of this paper have practical significance for the design and safe operation of HTS levitation system.

Superconducting liquid cryogen insulated power cables for medium voltage applications

Liquid Nitrogen (LN2) is used as the cryogen and is part of the dielectric insulation system in most high temperature superconducting (HTS) power cables. However, in electric propulsion systems for transportation, using LN2 is not feasible due to asphyxiation concerns in the event of a leak in a confined space. Gaseous helium (GHe) has been proposed as an alternate cryogen to relieve this asphyxiation concern. GHe has benefits such as a wider operating temperature range and versatility for a centralized cryogenic cooling system for multiple devices which could potentially reduce the overall weight of the superconducting system. The drawback is that GHe has a lower dielectric strength compared to LN2, which limits its use to low-medium voltage applications. A hybrid cryogen HTS cable was proposed using LN2 as the dielectric media and GHe as the cryogen of an HTS cable to solve the limitations and issues associated with each cryogen and explained in this paper. A 1-m prototype cable that used LN2 as the cryogen and dielectric was fabricated and dielectric breakdown measurements were performed on it to establish a baseline on what to be expected from the hybrid cryogen HTS cable.

Evaluation and dynamic breakup of bubble size distribution of liquified natural gas release underwater

With the demand for lower carbon emissions and the increasing use of clean energy instead of traditional fossil fuels, offshore production of liquefied natural gas (LNG) has become a major mode of energy transportation and storage. Due to its cryogenic characteristics, LNG produces special physical phenomena once it leaks from cargo ships or offshore pipelines. To investigate the mechanical behavior and thermal interaction between the jet-released LNG and surrounding ambient water, a set of laboratory experiments with various measurements was designed and developed to perform controllable cryogenic liquid horizontal release under water. The hydrodynamic phenomenon of flow behavior, effect of release dynamics, and instability mechanism of the breakup process caused by the formation of vapor bubbles were observed and quantified under different orifice sizes and release pressures. In addition, a four-stage physical model, established by Raj, that described the breakup dynamics transition from jet liquid to diffusion plume was validated and recorded using a visualized high-speed video camera. Two commonly used mathematical methods, the Rosin-Rammler distribution and lognormal distribution, were used to quantify and evaluate the average bubble sizes in 1.95 ± 0.06 mm, 2.18 ± 0.06 mm, and 2.2 ± 0.1 mm from 1, 3–5 mm, using image processing techniques. The bubble breakup mechanisms and empirical equations were developed and discussed with a complete set of literature data based on a non-dimensional analysis of various release conditions, which was validated with droplet size data obtained from laboratory studies in both gas and liquid co-flowing jets. The −0.38 power-law scaling relationship between the dimensionless length scale of d/lm and the mixture Weber number was established to predict the breakup of the vapor bubble size from subsea release fluids.

CFD simulation of heat transfer and phase change characteristics of the cryogenic liquid hydrogen tank under microgravity conditions

The heat transfer and phase change processes of cryogenic liquid hydrogen (LH2) in the tank have an important influence on the working performance of the liquid hydrogen-liquid oxygen storage and supply system of rockets and spacecrafts. In this study, we use the RANS method coupled with Lee model and VOF (volume of fraction) method to solve Navier-stokes equations. The Lee model is adopted to describe the phase change process of liquid hydrogen, and the VOF method is utilized to calculate free surface by solving the advection equation of volume fraction. The model is used to simulate the heat transfer and phase change processes of the cryogenic liquid hydrogen in the storage tank with the different gravitational accelerations, initial temperature, and liquid fill ratios of liquid hydrogen. Numerical results indicate greater gravitational acceleration enhances buoyancy and convection, enhancing convective heat transfer and evaporation processes in the tank. When the acceleration of gravity increases from 10−2 g0 to 10−5 g0, gaseous hydrogen mass increases from 0.0157 kg to 0.0244 kg at 200s. With the increase of initial liquid hydrogen temperature, the heat required to raise the liquid hydrogen to saturation temperature decreases and causes more liquid hydrogen to evaporate and cools the gas hydrogen temperature. More cryogenic liquid hydrogen (i.e., larger the fill ratio) makes the average fluid temperature in the tank lower. A 12.5% reduction in the fill ratio resulted in a decrease in fluid temperature from 20.35 K to 20.15 K (a reduction of about 0.1%, at 200s).

Design and optimization of the sustainable natural gas liquefaction process plant: A process system engineering approach

With the rapid development of the world economy and technologies, the energy demand is increasing. Based on the current regulations energy sectors need low-emission and low-carbon energy solutions. Natural gas (NG) is considered a green future fuel that is usually stored and transported as compressed gas or cryogenic liquid. The liquefied NG has 1/600th of its volume which helps in transportation. Liquefied natural gas (LNG) operations are the most energyintensive techniques. During refrigeration and liquefaction, the units of the LNG consume around ∼40−50% of the entire LNG supply chain energy. To date, the simplest single mixed refrigerant (SMR) cycle-based NG liquefaction plants have exergy efficiencies of around 26.97%. Moreover, the conventional SMR process utilizes a hydrocarbon-based mixed refrigerant (i.e., C1 to C3 and N2) mixture that is further harmful to the ecosystem. In this research work, it was found that the addition of eco-friendly hydro-fluoro-olefin (HFO123yf) with conventionally used refrigerants reduces energy consumption under the same conditions. Further hydraulic turbines were proposed to replace the expansion valves require for the Joule Thompson cooling effect that further increasing the process reversibility and energy efficiency. Hence, this research utilizes the optimization of the HFO based modified mixed refrigerant mixture (HSMR) for optimal operation of the LNG plant. The evaluated result shows that the proposed stochastic biogeography-based optimization (BBO) algorithm successfully reduces the overall energy consumption by 0.232 kW/kg-NG. This energy consumption is about 41.709 % compared to our base case study and it was 36% more efficient compared to the conventional SMR published study. This research further explores the sensitive decision variables that affect power consumption using the sensitivity analysis index method. The sensitivity indices may enable us to operate the plant in any abrupt changing or uncertain conditions when needed quick optimization using only a few key sensitive optimizing variables which are useful for real-time plant optimization. Moreover, the economic analysis of the proposed plant shows a total annualized cost of 6,158,000 USD with a 20% rate of return, per year.

Breakdown and Flashover Properties of Cryogenic Liquid Fuel for Superconducting Energy Pipeline

The cooling of cryogenic liquid fuel in a superconducting cable is an important technical means to realize efficient energy and power transmission. However, there are only few types of cryogenic liquid fuels that can maintain the superconducting strip below the critical temperature, and little is known about the insulating properties of fuels other than liquid hydrogen. Besides, cryogenic liquid fuels are flammable and explosive, and a safe operating procedure is essential to conduct the discharge tests. Based on the trinitrotoluene equivalent method, the safety distance of the discharge test is determined, and the safety precautions are summarized in this article. Taking the molar ratio of methane to propane as 3:1, the breakdown and flashover voltages of liquefied small molecular alkanes were studied, and the test of long-time withstand voltage was also carried out. At last, the discharge parameters and waveform, as well as the surface state of the polymer after flashover in the fuel, were analyzed. The breakdown field strength of cryogenic liquid fuel is 22.9 kV/mm, and the flashover field strength is 15.9 kV/mm. The reduction of breakdown strength is not found in the test of long-time withstand voltage. Therefore, it has some advantages for the liquid fuels to directly cool the superconducting strips from the cost and electrical performance. This study aims at the superconducting energy pipeline cooling by liquefied natural gas, and it can also provide technical references for the electrical property and safety research of other fuels.

CFD study on film boiling features of cryogenic fluid influenced by heat structures and gravity levels

Understanding bubble behaviors and thermal characteristics under various working conditions is of great significance to the efficient utilization of cryogenic propellants. In the present study, simulation models of pool film boiling at horizontal plate and cylinder surface are proposed with Volume of Fluid (VOF) method combined with Lee’s phase change model. Based on the physical and thermal performance, the gravity levels, physical properties, and heater structure dimensions are investigated respectively, which could satisfy the common application conditions of cryogenic propellants. The results show that the movement of bubbles at gas–liquid interface is critical to the pool film boiling heat transfer, and also the heat transfer mechanism affects the bubble motion behaviors. The critical wavelength and the most dangerous wavelength are significant length scales for the bubble behaviors in pool film boiling. When the cylindrical heater size is larger than the most dangerous wavelength, the bubble behaviors as well as the heat flux appear the similar characteristics with that at the plate heater surface. Moreover, the critical wavelength is approximately two times of the bubble departure diameter in the present cryogenic liquid boiling events, and the parameters, including liquid–vapor density difference, surface tension, and gas thermal conductivity, could affect the boiling heat flux significantly. In addition, under 0.03g condition, the bubble departure diameter could reach 27 mm and the boiling heat flux decreases to 800 W/m2, which are significantly different from that in normal gravity. In general, the present CFD model could execute a film boiling study accurately, and a series of detailed results on the bubble behaviors as well as the heat flux could be revealed.

Measurement of Compton Scattering at MAMI for the Extraction of the Electric and Magnetic Polarizabilities of the Proton

A precise measurement of the differential cross sections dσ/dΩ and the linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS setup. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-t dispersion relation model, constraining the fits with the Baldin sum rule, we have obtained the proton electric and magnetic polarizabilities with unprecedented precision: α_{E1}=10.99±0.16±0.47±0.17±0.34, β_{M1}=3.14±0.21±0.24±0.20±0.35; in units of 10^{-4} fm^{3} where the errors are statistical, systematic, spin polarizability dependent, and model dependent.

Combined thermoacoustic cooling and ortho-para conversion of cryogenic hydrogen

Hydrogen is a promising fuel for our future, as it can be produced with renewable energy sources and it does not emit harmful emissions when reacting with oxygen. To make the hydrogen economy viable, hydrogen needs to be transported as a dense cryogenic liquid. Since efficiencies of current cryocoolers are relatively low, improvements of the cooling technologies are required. In this study, an innovative solution involving thermoacoustic flow-through cooler is considered. Acoustic waves passing through porous medium can pump heat and cool hydrogen flowing through the system. An important feature of cryogenic hydrogen is the shift between its equilibrium ortho and para isomer fractions, which requires additional removal of heat. Since the natural conversion is slow, it must be augmented by catalysts for fast transition. The advantage of using the flow-through thermoacoustic system to cool hydrogen is that a catalyst can be placed in the porous matrix where hydrogen flows, so it can be cooled and undergo conversion at the same time. A mathematical model describing this process has been developed. Results showing achievable coefficients of performance, temperature drops, and flow rates of hydrogen are presented for both standing-wave and travelling-wave systems.