Hasil untuk "Low temperature engineering. Cryogenic engineering. Refrigeration"

M. Valant

Dhananjay Dubey, Rajdip Mukherjee, M. Singh

Superalloys are a group of engineering alloys designed to operate at elevated temperatures, and they find application in various engineering sectors where a high-temperature application is required such as nuclear power plants, steam turbines, and aircraft. There are three important classes of superalloys, that is, iron-based, cobalt-based, and nickel-based superalloys. Among them, nickel-based superalloys find great application at both low and high temperatures due to their higher mechanical strength, good fatigue life, excellent wear, and corrosive resistance. This review article aims to review the tribological studies of the nickel-based Inconel superalloys. The article deals with the systematic studies of wear behavior, wear mechanism, and nanostructured glaze layer formation over the wear surfaces. The effect of load and temperatures influencing the wear rate and wear mechanisms of nickel-based superalloys are also discussed in detail. Along with that, the focus of this review article is to discuss the advancement in the tribological studies of the Inconel-718 superalloy. The development in the Inconel-718 alloys (surface alloying, laser shot peening, composites, microstructure engineering, etc.) to improve wear resistance is also discussed in a systematic manner. This article is expected to assist the researchers in identifying the trend and research gaps so that they can contribute to further tribological developments of nickel-based superalloys.

H. Polat, F. M. Coelho, T. Vlugt et al.

An in-depth review of the available experimental and molecular simulation studies of CO2 diffusion in H2O, which is a central property in important industrial and environmental processes, such as carbon capture and storage, enhanced oil recovery, and in the food industry is presented. The cases of both bulk and confined systems are covered. The experimental and molecular simulation data gathered are analyzed, and simple and computationally efficient correlations are devised. These correlations are applicable to conditions from 273 K and 0.1 MPa up to 473 K and 45 MPa. The available experimental data for diffusion coefficients of CO2 in brines are also collected, and their dependency on temperature, pressure, and salinity is examined in detail. Other engineering models and correlations reported in literature are also presented. The review of the simulation studies focuses on the force field combinations, the data for diffusivities at low and high pressures, finite-size effects, and the correlations developed based on the Molecular Dynamics data. Regarding the confined systems, we review the main methods to measure and compute the diffusivity of confined CO2 and discuss the main natural and artificial confining media (i.e., smectites, calcites, silica, MOFs, and carbon materials). Detailed discussion is provided regarding the driving force for diffusion of CO2 and H2O under confinement, and on the role of effects such as H2O adsorption on hydrophilic confining media on the diffusivity of CO2. Finally, an outlook of future research paths for advancing the field of CO2 diffusivity in H2O at the bulk phase and in confinement is laid out.

Aaditya Bandgar

Pulse Tube Refrigerators (PTRs) have emerged as a promising cryogenic cooling technology due to their simplicity and reliability, devoid of moving parts at low temperatures. This study investigates the operational principles, design enhancements, and performance optimization of PTRs. Utilizing helium as the working gas, the system integrates critical components such as a pressure wave generator, regenerator, and heat exchangers to achieve effective cooling. Building on the foundational work by Gifford and Longsworth (1963) and subsequent modifications by Mikulin et al. (1984) and Radebaugh et al., the research focuses on optimizing phase angles and minimizing regenerator losses to enhance efficiency. Experimental trials were conducted by varying key parameters, including regenerator and pulse tube dimensions, orifice valve openings, and receiver tank volumes. Observed temperature reductions ranged from 7.6°C to 16.2°C, demonstrating the significant influence of design variables on cooling performance. The findings highlight the critical interplay between phase angle adjustments and regenerator effectiveness in achieving superior thermal performance. This study contributes to the advancement of PTR design, offering insights for applications in cryogenic systems and low-temperature engineering.

Sun Yanjun, Zheng Haiqi, Wang Shibiao et al.

In this work, absorption refrigerant working pairs consisting of four HFO refrigerants, R1234ze(E), R1234yf, R1233zd, and R1243zf, and ionic liquids were studied. The different ionic liquids contained 20 cations and 16 anions. The Henry′s law constant and solubility data of working pairs were simulated by the COSMO-RS method. The differences in Henry′s law constant and solubility between the different working pairs are discussed from the perspective of polarized charge density on the molecular surface. The polarized surface charge density curve of the R1234ze(E) refrigerant has a peak in the negative region. It is compatible with anions with a peak in the positive region. However, the compatibility with the peak in the negative region is poor. Ionic liquids with low Henry′s law constants and high solubilities were screened out when they were paired with HFO refrigerants.

К. Мане, Євгеній Сергійович Алексеїк

Pulsating heat pipes (PHP) are novel heat transfer devices which have wide prospects of application in energy, refrigeration, cryogenic systems and electronics cooling because of simple design and high efficiency of heat transfer. However, heat transfer characteristics of PHP depend on many parameters. This paper is dedicated to experimental investigation of the impact of heating zone length and angle of inclination on the start-up and operational characteristics of PHP. The investigation involved a systematic variation of the heating zone length and inclination angle with measuring of key performance indicators, including start-up heat flux density and temperature, transient heat flux density, and thermal resistance, for water, methanol and pentane as a heat carrier. 5-turn PHP made of copper capillary tube with inner diameter 1,1 mm was used as experimental sample. Main operational modes of PHP were defined and described in the paper based on obtained experimental data. Results indicate that increasing the heating zone length from 10 to 50 mm at all tested inclination angles significantly enhances the thermal performance of PHP by reducing start-up, transient heat flux densities and thermal resistance. Specifically, thermal resistance decreased by up to 51,8% and start-up, transient heat flux densities up to 68-71% with longer heating zone lengths. Also, it was shown that maximum transferred heat flux increased up to 59% with increasing in heating zone length. These findings suggest that optimizing heat zone length can improve start-up efficiency and overall heat transfer performance. The impact of inclination angle varies with the coolant used; generally, water outperforms methanol and pentane across all orientations. Methanol ranks next, with pentane showing the least performance. However, methanol and pentane are viable choices for low heat flux applications in vertical bottom heating mode. The study provides valuable insights for the design of PHP in energy, refrigeration and electronics cooling systems, highlighting the importance of heating zone (HZ) length configuration in achieving optimal performance

Liu Xiangzeng, Feng Wei, Zhang Gangan et al.

Experiments were conducted to study the condensation heat transfer and pressure drop characteristics of refrigerant R32 in aluminum herringbone tubes, ripple tubes, and smooth tubes. The experimental refrigerant mass flow rate is 100-350 kg/(m2·s). The saturation temperature is 308 K, 313 K, and 318 K, respectively, while the vapor quality is 0.2-0.8. The experimental results show that the herringbone tube has the highest coefficient of heat transfer, followed by the ripple tube, while the smooth tube is the worst. The friction pressure drop is highest for the ripple tube, and the pressure drop of the herringbone tube is higher than that of the smooth tube. The surface coefficient of heat transfer and friction pressure drop decrease with an increasing saturation temperature and increase with an increasing mass flow rate. The performance evaluation factor, PEF, was introduced to evaluate the heat transfer performance of the heat transfer tube. The herringbone tube has the best heat transfer performance with PEF values ranging from 2.07 to 2.72, while the ripple tube has PEF values ranging from 0.68 to 0.90. A new heat transfer correlation was proposed following the form of classical heat transfer correlations, and the error of the new correlation formula was within ±20%.

Aleksandr V. Pushkarev, Natalia Y. Saakyan

Local low-temperature impact on biological tissues, depending on the temperature reached, can lead to destructive, preserving or therapeutic effects. The article describes the principle of a unified approach for the transition from mass recommendations for the dosing of local low-temperature exposure to personalized. It is proposed to divide the exposure process into three stages: planning, provision and control, analysis of compliance with the planned and received dose. Examples of solving the problems of heat transfer in cryosurgery and cryopreservation are given for a possible improvement of the planning stage. In the framework of the first direction, two cases are considered. The first is to improve the accuracy of prostate cryoablation planning. The second is a comparison of the effectiveness of various materials of cryosurgical applicators: copper, brass and artificial sapphire, which can be used to influence and control the freezing zone by optical methods. Within the framework of the second direction, a case of using local low-temperature exposure to solve the problem of simultaneously preserving the framework of a biological tissue and removing a layer of donor cells, called decellularization, is shown for the purposes of transplantology. The results of the above examples can potentially be used in planning a local low-temperature impact. Based on this approach, it is possible to develop methods and technologies of a new generation with the possibility of accurate dosing.

Jinliang Liu, Fengshan Zhou, F. Deng et al.

Abstract Most of bentonite used in modern drilling engineering is physically and chemically modified calcium bentonite. However, with the increase of drilling depth, the bottom hole temperature may reach 180 °C, thus a large amount of calcium bentonite used in the drilling fluid will be unstable. This paper covers three kinds of calcium bentonite with poor rheological properties at high temperature, such as apparent viscosity is greater than 45 mPa·s or less than 10 mPa·s, API filtration loss is greater than 25 mL/30 min, which are diluted type, shear thickening type and low-shear type, these defects will make the rheological properties of drilling fluid worse. The difference is attributed to bentonite mineral composition, such as montmorillonite with good hydration expansion performance. By adding three kinds of heat-resistant water-soluble copolymers Na-HPAN (hydrolyzed polyacrylonitrile sodium), PAS (polycarboxylate salt) and SMP (sulfomethyl phenolic resin), the rheological properties of calcium bentonite drilling fluids can be significantly improved. For example, the addition of 0.1 wt% Na-HPAN and 0.1 wt% PAS increased the apparent viscosity of the XZJ calcium bentonite suspension from 4.5 to 19.5 mPa·s at 180 °C, and the filtration loss also decreased from 20.2 to 17.8 mL.

Zhiming Liu, Bin Jia, Yiyang Zhang et al.

A Pt/TiO2 catalyst fabricated via a sacrificial carbon layer strategy has been studied for the selective catalytic reduction of NOx with H2. Modified Pt/TiO2 exhibited superior low-temperature acti...

Zhang Rongrong, Zou Jiang, Sun Xiangli et al.

Direct refrigerant cooling has the advantages of low cost, high cooling efficiency, low weight, and high safety, and also problems of low evaporating temperature and uneven battery temperature in normal direct cooling refrigerant systems. In this study, the effectiveness of secondary throttling on the temperature regulation of a direct cooling plate was tested and verified. The results show that the direct cooling plate outlet pressure is increased while the superheat is reduced by adding a throttling device (fixed orifice device or a pressure-regulating valve with adjustable orifice) behind the cooling plate, thereby increasing the evaporation temperature and leading to better temperature uniformity. However, the throttle device with a fixed aperture cannot actively adjust the outlet pressure of the direct cooling plate, which increases as the thermal load increases. Therefore, it is difficult to control the battery temperature within an appropriate range when the thermal load changes. The throttle device with an adjustable aperture can adjust the direct cooling plate outlet pressure to a target value according to the operation load of the battery, which can not only avoid the evaporation temperature from being too low, but also improve the temperature uniformity.

Liu Xi, Li Yueling, Wang Jinhui et al.

Dynamic ice-making technology using supercooling water is expected to realize large-scale applications. In industry, the ultrasonic field is often used to release the supercooling state of supercooling water and generate ice slurry. In this study, the effect of different ultrasonic fields on the supercooling characteristics of crystallization, the size of the ice crystals, and the particle size distribution of ice crystals of 3% sodium chloride solution, were studied experimentally. The results showed that the introduction of an ultrasonic field of a certain power and frequency can quickly release the supercooling state. It was also found that the solution nucleation temperature was close to the ultrasonic irradiation temperature, and the ultrasonic field with high power and low frequency was more conducive to nucleation. The power, frequency and irradiation temperature were varied from 10.0 W to 40.0 W, 28 kHz to 40 kHz, and 0 ℃ to 4 ℃, respectively. The optimal ultrasonic field scheme was set as the power at 40.0 W, the frequency 28 kHz, and the irradiation temperature 2.0 ℃. An ultrasonic field can significantly reduce the crystal size. With the extension of the ultrasonic irradiation time after nucleation, the size of the ice crystals first increased and then leveled off. The changes in ultrasonic power and frequency had no obvious effect on the size of the ice crystals.

O. Rofman, A. Mikhaylovskaya, A. Kotov et al.

Abstract This study uses the stir-casting technique to combine a semi-solid AA2024 alloy directly with finely-sized β-SiCp embedded as a powder or with mechanically alloyed granules as a delivery agent. Liquid-state primary fabrication tends to form agglomerates of reinforcement particles, whereas rolling better distributes the composite constituents. Sub-micron reinforcements of low volume fractions do not significantly increase the hardness of the composite materials. Uniaxial tensile testing at elevated temperatures over a wide range of strain rates showed simultaneous increases in the ductility and crack resistance of AA2024 + SiCp granules embedded as a powder when compared to the non-reinforced control material at lower strain rates, with the same toughness as the control material. The maximum engineering strain of 252.7 ± 19.2% was observed in AA2024/SiCp at a strain rate of 10−4 s−1. This improvement in properties is attributed to grain refinement in the MMCs, leading to pinning events during the straining and ductility increases. The resultant impediments to grain growth and crack propagation allow the fine-sized reinforcements to control dynamic microstructural changes during fatigue. Cube {001} is a dominant texture component in AA2024, whereas the Goss {011} and S {123} components mainly represent the texture of the discontinuously reinforced aluminum matrix.

Saleh S. Baakeem, J. Orfi, A. Alabdulkarem

P. Kaczyński, M. Ptak, J. Wilhelm et al.

Abstract Agglomerated cork, made from the scraps of wine stoppers, has been finding a wide set of applications due to its excellent thermal and acoustic insulation properties. The random orientation of grains makes the material nearly isotropic, while its dominant viscoelastic behaviour and nearly zero Poisson's ratio make the material also very interesting in applications where dimensional stability is highly demanded. With proven properties, agglomerated cork has been widely used for manufacturing of architectural facades, in civil construction, aerospace engineering and even home appliances production. For outdoor applications, the performance of cork material under different working temperatures is a vital point to be considered. This paper assesses the capability of five different types of cork agglomerates to withstand 500 J impact energy under different temperature conditions. Keeping 11.2 kg impact mass and velocity of 9.2 m/s, impact tests were performed for a wide range of temperatures starting from sub-zero temperature (−30 °C) up to 100 °C in order to cover a full span of working circumstances. Results show significant variations of amount of absorbed energy depending on testing temperature, calling the attention of designers and product developers for important aspects to be considered upon the application of this material under extreme weather conditions.

G. B. Narkhede, S. Chinchanikar, S. S. Vadgeri et al.

Hast alloys, wasp alloys and tool steels are the most commonly used materials in nuclear engineering and aerospace industries. However, these materials are considered to be “Difficult to machine” which attracted several researchers to work in this domain with a view to obtain optimum machining performance. The present work explored the comparative evaluation of machining performance of Inconel 625 under dry and cryogenic cutting conditions from an industrial perspective with emphasis on cutting forces, tool-chip interface temperature, surface finish and tool life. Turning experiments which were planned using the orthogonal array of L27were carried out using Tungsten carbide Al2O3 coated inserts varying the cutting speed, feed and depth of cut. Cutting forces generated during turning at varying cutting conditions were measured using three axis lathe tool dynamometer. It was found the combination of speed of 200 m/min, feed value of 0.04 mm/rev and depth of cut value of 0.2 mm gives the optimum cutting forces with superior surface finish and low tool chip interface temperature in dry cutting condition. Again for same combination of cutting parameters were tested with cryogenic coolant Liquid Nitrogen ( LN2) and it was observed that cutting forces reduced up to 30%, surface roughness improved by 31.37% and temperature reduced by 71.67%.

Weiqiang Song, Xian Shi, Chunguang Wang et al.

Cryogenic nitrogen fracturing is an attractive method for stimulating underground reservoir, since it could favorably induce complex fracture due to the huge temperature difference with lower injection pressure and with the replacement of current water‐based fracturing fluid. However, the concern about whether cryogenic nitrogen would be overheated remains unrevealed in the engineering environment with large wellbore length. In addition, reservoir stimulation results are also related with the pressure state at bottom hole. Therefore, in this study, a mathematical model was proposed to predict the radial heat transfer and its influence on vertical pressure transmission in the wellbore with cryogenic nitrogen as fracturing fluid. The model fully couples the heat transfer, hydraulics, and the compressibility of nitrogen, and then, the calculation results were presented and analyzed through a case study. According to the results, the temperature of nitrogen increases too fast under conventional engineering conditions, and it changes into gaseous state at the depth lower than 100 m. Finally, the temperature difference between nitrogen and formation rock becomes too minimal to induce thermal stress at bottom hole. Due to the fast temperature increase, the density of nitrogen decreases too much, and the vertical pressure increasing rate by liquid nitrogen (1.66 MPa/km) is merely 18.2% that in carbon dioxide fracturing (9.13 MPa/km). The results indicate that utilization of special casing with much larger thermal resistance is an indispensable approach to realize the feasibility and advantages of cryogenic nitrogen fracturing.

Li Shuai, Qian Chenlu, Li Dong et al.

After traditional thermal defrosting, a great number of water droplets still retain on the surface, which can become the base of secondary frosting and accelerate secondary frosting. Therefore, duly removing retained droplets after defrosting is of great importance. In this paper, the frost melting evolution on a superhydrophobic surface was visually observed and the effects of the surface inclination angle on defrosting droplet drainage from a bare surface and superhydrophobic surface (with a static contact angle of 88.0°and 151.1°respectively) were comparatively analyzed. The experimental results showed that the defrosting droplets, as an ice-water mixture, suspended on asuperhydrophobic surface with a Cassie state during the defrosting process on a horizontal superhydrophobic surface. Two kinds of behaviors, namely, single-film curling and multi-droplets coalescence, can be seen during the defrosting processes, due to a large static contact angle and tiny contact angle hysteresis. Most of defrosting droplets on an inclined superhydrophobic surface can be self-drained accompanied with ice-water mixture rolling and stripping, which differ from the bare surface. When the inclination angle is greater than 30°, the drainage ratio of the superhydrophobic surface can reach more than 90%, while that of the bare surface can only reach 70%. Furthermore, mechanical analysis of droplets on an inclined surface was applied. The critical droplet-slipping radius was deduced according to the surface wetting characteristics and surface inclination angle, which were consistent with the experiment results.

Zhou Liqiang, Zhang Hua, Wang Zilong et al.

A hot water tank test bench with phase change material (PCM) of sodium acetate trihydrate was built. The thermodynamic characteristics of the water tank were tested under the conditions of an initial water temperature of 80 °C and an inlet water temperature of 5 °C. The analytical method and the enthalpy efficiency analysis method were used to analyze the thermal stratification characteristics of the hot water storage tank with PCM when the influent flow rates were 1 L/min, 3 L/min, 5 L/min, 7 L/min, and 9 L/min, respectively. The experimental results show that when the water tank temperature was 80 ° C, the energy of the ordinary water tanks, PCM48 and PCM58, were 18.81 MJ, 19.34 MJ, and 19.07 MJ, respectively. When the inlet flow rate was the same, the closer the heat storage ball with PCM is to the water tank inlet, the better the heat stratification effect of the water tank. As the influent flow rate increased, the stratification effect decreased. The number of Ri in different water tanks reached a maximum at t*=0.5; the number of Ri decreased with the lower position of the heat storage ball with PCM. The Ri number of the PCM48 and PCM58 in the fourth layer were 7.569 and 7.78, respectively. The Ri numbers at the layer were reduced to 7.03 and 7.145, respectively, indicating that the degree of thermal stratification of the tank decreased with the higher position of the heat storage ball with PCM.

Kai Wei, X. Wang, Xujing Yang et al.

Abstract Consider the severe thermal loads in thermal engineering applications of lightweight ZrO2 and ZrB2 corrugated sandwich structures, here, their heat transfer mechanism and characteristics are originally explored in this work. Finite element (FE) models for heat transfer of ZrO2 and ZrB2 sandwiches, sandwiches filled with insulation material and the corresponding bulk ceramics are respectively well established. The insulation efficiency, temperature gradient, thermal short effect and thermal-mechanical coupling effect are well calculated and analyzed. It is found that cavity radiation heat flux is increased with the height, leading to low insulation efficiency. The insulation material can block the cavity radiation, and hence can remarkably enhance the insulation efficiency and improve the temperature uniformity. Low temperature gradient is found in ZrO2 and ZrB2 sandwiches, while, remarkable temperature gradients are found in sandwiches filled with insulation material. With the increasing height, the insulation effect is improved, while the mechanical properties are weakened, suggesting pronounced thermal-mechanical coupling effect between loading bearing capacity and insulation effect. The heat transfer mechanism and characteristic revealed here provide the thermal basis for engineering applications of the ZrO2 and ZrB2 cellular sandwiches.