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Journal articles on the topic 'Cryogenic HEMT LNA'
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Jayakody, Harith, Raya Al-Dadah, and Saad Mahmoud. "Cryogenic Energy for Indirect Freeze Desalination—Numerical and Experimental Investigation." Processes 8, no. 1 (December 21, 2019): 19. http://dx.doi.org/10.3390/pr8010019.
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Renewed interest in freeze desalination has emerged due to its advantages over other desalination technologies. A major advantage of the freeze desalination process over evaporative methods is its lower energy consumption (latent heat of freezing is 333.5 kJ/kg and latent heat of evaporation is 2256.7 kJ/kg). Cryogenic fluids like LN2/LAir are emerging as an effective energy storage medium to maximise utilisation of intermittent renewable energy sources. The recovery of this stored cold energy has the potential to be used for freeze desalination. Computational Fluid Dynamics (CFD) modelling was developed to simulate the evaporation of liquid nitrogen to simultaneously conduct freeze desalination to investigate the feasibility of using cryogenic energy for freeze desalination. This integrated CFD model was validated using experimental heat exchanger test facility constructed, to evaporate liquid nitrogen to supply the cooling required for freezing. Parametric study on the LN2 flow rate to observe the volume of ice obtained was also examined using CFD, where increasing the velocity of LN2 by 6 times, increased the volume of ice obtained by 4.3 times. A number of freezing stages were required in order to reduce the ice salinity from 1.5% down to 0.1% as regarded by the World Health Organisation (WHO) as safe to drink. In the cryogenic desalination test rig, approximately 1.35 L of liquid nitrogen was required to reduce the ice salinity from 1.5% to less than 0.1%. Furthermore, the above results illustrate the potential of using the cold energy of cryogenic fluids such as Liquified Natural Gas (LNG) and LN2/LAir for freeze desalination applications as most cold energy during LNG regasification has been unexploited today.
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Khanna, Rohit, and Bikramjit Basu. "Low friction and severe wear of alumina in cryogenic environment: A first report." Journal of Materials Research 21, no. 4 (April 1, 2006): 832–43. http://dx.doi.org/10.1557/jmr.2006.0104.
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Structural ceramics are considered as potential candidate materials for use in hybrid bearings in rocket turbopumps, operated under high stress in cryogenic environment. The friction and wear-related surface failure is considered as one of the critical factors in selecting the materials for cryo-turbopumps of Space Shuttle Main Engine (SSME). To obtain fundamental understanding of the tribological properties of ceramics in cryogenic environment, a very first set of sliding wear tests were carried out on self-mated Al2O3, a model brittle ceramic material, in liquid nitrogen (LN2) under varying load (2–10 N) and high rotational speed of 2550 rpm, using a newly designed cryogenic tribometer. The present research attempts to answer some important questions: (i) What would be the influence of LN2 on frictional and fracture behavior at sliding contacts? (ii) How does the material removal process occur in LN2 environment? Our experimental results reveal that self-mated alumina exhibits low steady-state coefficient of friction ∼0.13–0.18 and suffers from high wear rate (10−5 mm3/Nm) under the selected testing conditions. The novelty of the present work also lies in presenting some interesting results, for the first time, concerning the deformation and fracture of alumina at cryogenic temperature under high speed sliding conditions. Detailed scanning electronic microscope observation of the worn surfaces indicates that severe damage of both ball and flat occurs in cryogenic environment by transgranular and intergranular fracture. The observed wear behavior is explained in terms of thermal heat dissipation and brittle fracture of alumina in LN2.
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SONG, Younguk(Benedict). "A Study of Cryogenic ORC Application on the LNG Carriers using Cold Heat and Sea Water." JOURNAL OF FISHRIES AND MARINE SCIENCES EDUCATION 30, no. 3 (June 30, 2018): 839–49. http://dx.doi.org/10.13000/jfmse.2018.06.30.3.839.
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Butterick, Charles J. "Liquid Nitrogen Safety." Microscopy Today 4, no. 5 (June 1996): 3–4. http://dx.doi.org/10.1017/s1551929500068887.
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Recent Internet postings on the Microscopy listserver indicate paradoxical views on the personal protective equipment (PPE) necessary to handle liquid nitrogen (LN2) safely. Those views range from full protective gear to, somewhat facetiously, complete nudity. The crux of the paradox is that both extremes have points of validity.The gist of preventing frostbite or cold injury to the skin is to prevent continuous contact with LN2. The physics of the Leidenfrost effect (LE) protects the skin from momentary contact or splashes of LN2. A layer of gas between the LN2 and the skin prevents significant heat transfer from the skin, stopping damage. The LE does not apply to inadvertent splashes of LN2 to the cornea. Alternatively, using protective equipment insulates the skin and prevents trapping of the cryogen by allowing the LN2 to run off.
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Butterick, Charles J. "Liquid Nitrogen Safety." Microscopy Today 4, no. 3 (April 1996): 3–4. http://dx.doi.org/10.1017/s1551929500067870.
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Recent Internet postings on the Microscopy listserver indicate paradoxical views on the personal protective equipment (PPE) necessary to handle liquid nitrogen (LN2) safely. Those views range from full protective gear to, somewhat facetiously, complete nudity. The crux of the paradox is that both extremes have points of validity.The gist of preventing frostbite or cold injury to the skin is to prevent continuous contact with LN2. The physics of the Leidenfrost effect (LE) protects the skin from momentary contact or splashes of LN2. A layer of gas between the LM2 and the skin prevents significant heat transfer from the skin, stopping damage. The LE does not apply to inadvertent splashes of LN2 to the cornea. Alternatively, using protective equipment insulates the skin and prevents trapping of the cryogen by allowing the LN2 to run off.
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Patil, Sandip, Pravin Pawar, Swapnil Kekade, Sachin Patil, Kiran Gujar, and R. K. P. Singh. "Effect of Gas Based Coolant Lubricants on Machinability of Titanium Alloy Ti6Al4V." Key Engineering Materials 705 (August 2016): 233–39. http://dx.doi.org/10.4028/www.scientific.net/kem.705.233.
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Machining of titanium alloys generates enormous amount of heat at the chip-tool interface leading to poor machinability. Use of coolants in the form of gas based lubricants is another approach for controlling the temperature at the cutting zone. The current research investigates the effect of gaseous cooling using CO2 and cryogenic cooling using LN2 at the tool rake face during machining of Ti6Al4V. The effect of both the cutting environments was analyzed at low and high level of cutting conditions through FE Model highlighting on thermal softening and through the experimental output responses emphasizing on cutting forces, surface finish and chip microstructure, etc.
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Hu, Hai-Ping. "The surface tension effects in boiling heat transfer of cryogenic LN2 on an ellipsoid." Nuclear Engineering and Design 240, no. 1 (January 2010): 139–45. http://dx.doi.org/10.1016/j.nucengdes.2009.08.026.
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Florio, Ciro, Gabriella Fiorentino, Fabiana Corcelli, Sergio Ulgiati, Stefano Dumontet, Joshua Güsewell, and Ludger Eltrop. "A Life Cycle Assessment of Biomethane Production from Waste Feedstock Through Different Upgrading Technologies." Energies 12, no. 4 (February 22, 2019): 718. http://dx.doi.org/10.3390/en12040718.
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Upgrading consists of a range of purification processes aimed at increasing the methane content of biogas to reach specifications similar to natural gas. In this perspective, an environmental assessment, based on the Life Cycle Assessment (LCA) method, of different upgrading technologies is helpful to identify the environmental characteristics of biomethane and the critical steps for improvement. The aim of this work is to conduct an LCA of biomethane production from waste feedstock, using the SimaPro software. The study focuses on the comparison of several upgrading technologies (namely, membrane separation, cryogenic separation, pressure swing adsorption, chemical scrubbing, high pressure water scrubbing) and the on-site cogeneration of electricity and heat, including the environmental benefits deriving from the substitution of fossil-based products. The results show a better environmental performance of the cogeneration option in most of the impact categories. The Fossil resource scarcity is the impact category which is mainly benefited by the avoided production of natural gas, with savings of about 0.5 kg oil eq/m3 of biogas for all the investigated technologies, with an average improvement of about 76% compared to conventional cogeneration. The results show that the membrane upgrading technology is slightly more environmentally convenient than the other upgrading technologies.
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Jamil, Muhammad, Ning He, Wei Zhao, Liang Li, Munish Kumar Gupta, Murat Sarikaya, Aqib Mashood Khan, and Rupinder Singh. "Heat Transfer Efficiency of Cryogenic-LN2 and CO2-snow and their application in the Turning of Ti-6AL-4V." International Journal of Heat and Mass Transfer 166 (February 2021): 120716. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2020.120716.
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Xin-hai, ZHANG, DOU Kai, ZHANG Guo-wei, LI Xun-guang, CHENG Wang-shou, and ZHU Hui. "Preparation of CO2/N2 cryogenic slurry and its pipeline flow characteristics." E3S Web of Conferences 233 (2021): 01068. http://dx.doi.org/10.1051/e3sconf/202123301068.
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It was proposed to use CO2/N2 to effectively prevent and control Class A solid spontaneous fires such as coal. The preparation process of CO2/N2 cryogenic slurry pipeline and its pipeline flow characteristics were studied. The temperature field, pressure field and phase change characteristic changed during the transportation of the CO2/N2 mixture in the pipeline are analyzed by numerical simulation. The results showed that: the fluid in the pipeline exchanged heat and started to contact at a position of 0.1m in the pipeline. The temperature first rapidly dropped to the lowest temperature of 103K, and then the fluids in the range of 0.1m to 0.3m were fully mixed, and the temperature rised to 164K. The temperature was consistent with the equilibrium state in the pipe, and the temperature was gentle and stable; the pressure in the pipe was on the whole downward trend, and each position along the main pipe produced a positive pressure difference relative to the end of the pipe. The closer to the mixing place, the greater the corresponding pressure difference; During the mixing process, LN2 was acted as a cold source to sublime CO2 to form dry ice particles. And through the cryogenic fluid mixing experiment, the temperature distribution in the pipeline, range of the dry ice particle generation position, and the dry ice particle generation phenomenon was measured. The results showed that the mixing was completed within 0.8 m of the pipeline, and the temperature in the tube rised to 168K and remain stable. The data were basically consistent. And dry ice particles generated at the temperature of 194.5K, and a diffuse gas cloud formed at the outlet with the momentum of the jet.
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Yoon, Jung-In, Kwang-Hwan Choi, Chang-Hyo Son, Jin-Woo Kwag, and Seung-Moon Baek. "Characteristics of Cryogenic Cascade Refrigeration Cycle for Liquefaction of Natural Gas with the Pressure Drop of Heat Exchanger." Journal of the Korean Society of Marine Engineering 36, no. 6 (September 30, 2012): 756–61. http://dx.doi.org/10.5916/jkosme.2012.36.6.756.
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Darr, S. R., J. W. Hartwig, J. Dong, H. Wang, A. K. Majumdar, A. C. LeClair, and J. N. Chung. "Two-Phase Pipe Quenching Correlations for Liquid Nitrogen and Liquid Hydrogen." Journal of Heat Transfer 141, no. 4 (February 27, 2019). http://dx.doi.org/10.1115/1.4041830.
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Recently, two-phase cryogenic flow boiling data in liquid nitrogen (LN2) and liquid hydrogen (LH2) were compared to the most popular two-phase correlations, as well as correlations used in two of the most widely used commercially available thermal/fluid design codes in Hartwig et al. (2016, “Assessment of Existing Two Phase Heat Transfer Coefficient and Critical Heat Flux on Cryogenic Flow Boiling Quenching Experiments,” Int. J. Heat Mass Transfer, 93, pp. 441–463). Results uncovered that the correlations performed poorly, with predictions significantly higher than the data. Disparity is primarily due to the fact that most two-phase correlations are based on room temperature fluids, and for the heating configuration, not the quenching configuration. The penalty for such poor predictive tools is higher margin, safety factor, and cost. Before control algorithms for cryogenic transfer systems can be implemented, it is first required to develop a set of low-error, fundamental two-phase heat transfer correlations that match available cryogenic data. This paper presents the background for developing a new set of quenching/chilldown correlations for cryogenic pipe flow on thin, shorter lines, including the results of an exhaustive literature review of 61 sources. New correlations are presented which are based on the consolidated database of 79,915 quenching points for a 1.27 cm diameter line, covering a wide range of inlet subcooling, mass flux, pressure, equilibrium quality, flow direction, and even gravity level. Functional forms are presented for LN2 and LH2 chilldown correlations, including film, transition, and nucleate boiling, critical heat flux, and the Leidenfrost point.
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Shi, Bin, Ahmed Elsayed, Ahmed Damir, Helmi Attia, and Rachid M'Saoubi. "A Hybrid Modeling Approach for Characterization and Simulation of Cryogenic Machining of Ti–6Al–4V Alloy." Journal of Manufacturing Science and Engineering 141, no. 2 (January 4, 2019). http://dx.doi.org/10.1115/1.4042307.
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A hybrid modeling approach based on computational fluid dynamics (CFD) and finite element method (FEM) is presented to simulate and study cryogenic machining (CM) of Ti–6Al–4V alloy. CFD analysis was carried out to study the characteristics of the fluid flow and heat transfer process of liquid nitrogen (LN2) jet used as a coolant in turning operation. The velocity, turbulence, gas volume fraction, and temperature of the impingement jet were investigated. Based on the analysis results, the coefficient of heat transfer (CHT) between the LN2 and cutting tool/insert was obtained and used in the FEM analysis to model the heat transfer process between the LN2 and the tool/chip/workpiece. A three-dimensional (3D) finite element (FE) model was developed to simulate a real CM operation. CM tests were carried out to validate the 3D FE model by comparing cutting forces and chip temperature. To evaluate LN2 cooling effect on tool temperature and tool wear, a two-dimensional (2D) FE model was developed for steady-state thermal analysis of cryogenic and dry machining. Based on the predicted temperatures, the tool wear was estimated, showing that LN2 cooling can significantly improve tool life.
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Sun, Shan, Jinju Sun, Wanyou Sun, and Peng Song. "Enhancing Cryogenic Cavitation Prediction Through Incorporating Modified Cavitation and Turbulence Models." Journal of Fluids Engineering 143, no. 6 (March 4, 2021). http://dx.doi.org/10.1115/1.4050056.
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Abstract Cavitating flow prediction is essential for designing cavitation-resistant hydraulic machines. Despite the advances achieved in normal-temperature cavitation prediction, cryogenic cavitation prediction has remained a challenging task in which thermal effects play a significant role. This study aims to enhance the prediction of cryogenic cavitation, and both the cavitation and turbulence models are improved simultaneously. The original cavitation model embedded in the CFX flow solver is modified by incorporating additional source terms (such as mass and heat transfer rates) for dual evaporation and condensation processes. The renormalization group k–ε turbulence model is modified on the basis of the filter-based turbulence model and density correction method to permit a smooth prediction of turbulence eddy viscosity, which mitigates the overestimation of the turbulence length scale in the cryogenic cavity (which is intrinsic to the original renormalization group k–ε turbulence model). The modified cavitation and turbulence models are implemented through CFX Expression Language (CEL) within the CFX frame. To verify the modified models and the enhancement of cryogenic cavitation prediction, Hord's liquefied nitrogen (LN2) and liquefied hydrogen (LH2) experiments over a hydrofoil and ogive are used, and cavitating flow simulation is conducted for each of the test cases. When using the modified models, the predicted temperature and pressure curves agree well with the measured values, and the predicted cavity lengths are much closer to the measured lengths. It is proven that the cryogenic cavitating flow can be well depicted by the modified models.
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"Feasibility Analysis on Cryogenic Properties of Supercritical Nitrogen to be used in the Cooling of Hg-Based High Temperature Superconductors for Electric Aircraft Propulsion." International Journal of Engineering and Advanced Technology 9, no. 1S3 (December 31, 2019): 106–10. http://dx.doi.org/10.35940/ijeat.a1022.1291s319.
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Electrified Aircraft Propulsion (EAP) and Advanced Hybrid Electric Aircrafts (AHEA) like NASA NX-3, SUGAR, NASA X-57 and STARC ABL are going to be the future of avionics as they have potential to improve fuel economy, emissions and noise levels. The agencies have suggested using superconducting cables for the electric transmission to reduce heat losses. The limit of critical current has reached 134 K where Hg- based ceramic materials are available that can superconduct at this temperature range. In order to retain the superconductivity, the cables have to be cooled below its critical temperature. Liquid nitrogen (LN2) boils of at 77 K which further leads to multiphase heat transfer challenges. An attempt has been made in the present work to overcome such challenges and a novel concept of using Supercritical Nitrogen (SCN), having critical temperature 126.19K and pressure as 3.3958MPa (consist single phase), as a cryogen for the cooling of Hg-Based Superconductors, has been introduced. Drastic variations have been found for thermophysical properties of SCN near the critical point. It has been concluded that few temperature and pressure ranges are suitable if one wants to incorporate SCN as cryogen for Hg-based superconductors.
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Bañuelo. Linares, A., K. Berrisford, L. Kellam, and A. Campbell. "P–126 A comparison of the efficacy of sperm freezing using high security tubes versus high security straws." Human Reproduction 36, Supplement_1 (July 1, 2021). http://dx.doi.org/10.1093/humrep/deab130.125.
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Abstract Study question Are there any advantages in using High security tubes rather than High Security straws for conventional slow sperm freezing? Summary answer Freezing sperm in High Security tubes (HST) improved post-thaw recovery rate and motility, and also reduced processing and handling compared to High Security straws (HSS). What is known already The use of High Security freezing consumables (HSFC) in an IVF setting is a safe and effective way of eliminating concerns related to viral cross-contamination during storage. The lower diameter of HSS does make them susceptible to warming during handling. The HSFC used in this study is the only CE marked products that are made of resin, leak-proof and shatter-proof in all cryogenic temperatures even in LN2. No previous studies have compared the use of HST with HSS for conventional human sperm freezing. This study sets out to investigate the performance of HST compared to HSS. Study design, size, duration The study was designed as a controlled split-sample study with blind post-thaw analysis. Following the routine WHO analysis of 20 semen samples, the remainder of each of the samples was evenly divided and cryopreserved by conventional slow freezing in each of the two different HSFC. The freeze was conducted simultaneously by the same practitioner, employing the same freezing protocol and cryoprotectant. The pre-freeze and post-thaw concentration, total and progressive sperm motility were recorded. Participants/materials, setting, methods At one IVF clinic, semen samples with sperm density ≥15million/ml, ≥40% motility, ≥1.5ml were included. Cryoprotectant (SpermFreeze, Fertipro) was added dropwise to unprepared semen and kept at room temperature for 10 minutes before loading into HSFC (0.5ml CBS™HSS; CBS™HST). HSFC were heat-sealed (SYMS; SYMSIII sealers) and placed in vapour for 30 minutes before plunging into LN2. Samples were thawed by immersion in a 37Cº water bath for 5 minutes and analysed using WHO methods. Main results and the role of chance Paired-t test was used to compare the percentage motility between the different HSFC. All analysis was considered statistically significant when p < 0.01. We demonstrated that the sperm recovery rate (Percentage total motility post-thaw/ Percentage total motility pre-freeze) in HST was 66.63 ± 14.94 (mean ± standard deviation) compared to 40.80 ± 14.69 in HSS. In the HSS, the percentage post-thaw total motility was 19.99 ± 7.21 and the percentage post-thaw progressive motility was 12.26 ± 2.59. In the HST, the percentage post-thaw total motility was 32.57 ± 8.33 and the percentage post-thaw progressive motility was 23.08 ± 5.53. The overall improvement when using HST against HSS was 12.53 ± 5.69, 10.44 ± 5.29 for the total motility and the progressive motility respectively. Comments were recorded regarding the handling and the condition of the HSS and HST for each freeze event. Neither device displayed any leakage of LN2 or any explosion during the warming. The freezing process was easier and faster using HST rather than HSS. It was also noted that the entire sample can be recovered from the HST, unlike the HSS. Limitations, reasons for caution The study looked at sperm recovery in terms of motility only. DNA damage was not considered as a parameter of sperm quality. Also, fertilization, pregnancy rates, live birth rates and the use of poorer quality sperm samples have not been investigated. Wider implications of the findings: For conventional sperm freezing, the use of HST resulted in improved sperm motility and progression post-thaw, when compared to HSS. This finding supports the use of HST to improve the post thaw quality of sperm, benefitting patients with own frozen samples, recipients of donor sperm and donor sperm banks. Trial registration number Not applicable.