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

Giacomo Jarc, S. Y. Mathengattil, Angela Montanaro et al.

Cavity-mediated thermal control of metal-to-insulator transition is achieved by embedding the charge density wave material 1T-TaS_2 into cryogenic tunable terahertz cavities. Placing quantum materials into optical cavities provides a unique platform for controlling quantum cooperative properties of matter, by both weak and strong light–matter coupling^ 1 , 2 . Here we report experimental evidence of reversible cavity control of a metal-to-insulator phase transition in a correlated solid-state material. We embed the charge density wave material 1T-TaS_2 into cryogenic tunable terahertz cavities^ 3 and show that a switch between conductive and insulating behaviours, associated with a large change in the sample temperature, is obtained by mechanically tuning the distance between the cavity mirrors and their alignment. The large thermal modification observed is indicative of a Purcell-like scenario in which the spectral profile of the cavity modifies the energy exchange between the material and the external electromagnetic field. Our findings provide opportunities for controlling the thermodynamics and macroscopic transport properties of quantum materials by engineering their electromagnetic environment.

Muhammad Wajid Ullah, M. Ul-Islam, Adeeb Shehzad et al.

3D printing, particularly bioprinting, has emerged as a transformative technology in tissue engineering and regenerative medicine, enabling the precise layer‐by‐layer fabrication of living tissues and complex biomaterials. Bioprinting has evolved through advances in printing methods such as fused deposition modeling (FDM), stereolithography (SLA), powder bed fusion (PBF), and jetting techniques, each offering distinct advantages for producing high‐resolution, functional constructs. Central to bioprinting is the development of bioinks, primarily composed of natural and synthetic polymers and microbial polysaccharides, which must balance biocompatibility, mechanical integrity, and printability to support viable cell encapsulation and tissue formation. Despite remarkable progress, challenges persist, including optimizing bioink viscosity, cell viability, scaffold structural and functional complexities (vascularization, in vivo functionality), degradation rates, and scalability, as well as addressing regulatory and ethical concerns. Recent innovations, such as cryogenic printing, offer promising solutions by preserving cell viability and enhancing structural fidelity under ultra‐low temperatures. While 3D printing holds immense potential to revolutionize personalized medicine, organ fabrication, and sustainable manufacturing, current technological, biological, and economic constraints temper expectations. Continued interdisciplinary research, material innovation, and refinement of printing technologies are essential to translate 3D bioprinting from experimental platforms to clinical and commercial realities, fulfilling its promise as a cornerstone of next‐generation regenerative therapies and advanced manufacturing.

C. Sahoo, B. Swain, Manjula Das et al.

XueLing Zhang, XuHan Zhang, Chun Duan

Xia Yang, Jiang Ziqi, Zhang Bin et al.

To investigate the vapor injection performance of a scroll compressor with a short profile, a three-dimensional transient numerical model of a vapor-injection scroll compressor for an electric vehicle with a displacement of 38 cm³/r is established and verified with deviations within 9.5%. We investigated the effects of the pressure and temperature of vapor injection on the performance of the scroll compressor using the model. The results show that under the condition of a constant superheat, with an increase in injection pressure, the discharge temperature of the compressor initially decreases and then gradually increases. Moreover, the heating capacity exhibits an increasing trend, with the maximum increase in heating capacity reaching 20.5% and 17.1% at rotary speeds of 5 000 and 6 000 r/min, respectively. In addition, the heating coefficient of performance (COP) increases during the first stage and then decreases. Moreover, the maximum values of the heating COP with vapor injection at the former speeds were 3.9% and 2.3% higher than those without vapor injection, respectively. The compressor efficiency exhibits the same tendency as the heating COP, and the volumetric efficiency gradually decreases. The compressor discharge temperature increases slightly with constant injection pressure, whereas the compressor power, heating capacity, and heating COP remain almost constant as the injection temperature increases. Compared with the injection temperature, the injection pressure has a significant impact on the scroll compressor.

S. Bera, R. Mitra, Joginder Singh

ABSTRACT Carotenoids are fat-soluble bio pigments often responsible for red, orange, pink and yellow coloration of fruits and vegetables. They are commonly referred as nutraceutical which is an alternative to pharmaceutical drugs claiming to have numerous physiological benefits. However their activity often get disoriented by photonic exposure, temperature and aeration rate thus leading to low bioavailability and bio accessibility. Most of the market value for carotenoids revolves around food and cosmetic industries as supplement where they have been continuously exposed to rigorous physico-chemical treatment. Though several encapsulation techniques are now in practice to improve stability of carotenoids, the factors like shelf life during storage and controlled release from the delivery vehicle always appeared to be a bottleneck in this field. In this situation, different technologies in nanoscale is showing promising result for carotenoid encapsulation and delivery as they provide greater mass per surface area and protects most of their bioactivities. However, safety concerns related to carrier material and process must be evaluated crucially. Thus, the aim of this review was to collect and correlate technical information concerning the parameters playing pivotal role in characterization and stabilization of designed vehicles for carotenoids delivery. This comprehensive study predominantly focused on experiments carried out in past decade explaining how researchers have fabricated bioprocess engineering in amalgamation with nano techniques to improve the bioavailability for carotenoids. Furthermore, it will help the readers to understand the cognisance of carotenoids in nutraceutical market for their trendy application in food, feed and cosmeceutical industries in contemporary era. Graphical Abstract

L. Wong, X. Cui, Yahui Zhang et al.

It is well documented that temperatures higher than 400 ℃ can significantly lower rock strength due to thermally induced decomposition and microcracks. However, rock strength increase under temperatures 25–400 ℃ has also been reported. It remains elusive whether thermal strengthening does exist or it is just an illusion caused by rock heterogeneity. To uncover such a mystery, we carried out triaxial compression tests on Sichuan marble under 25–200 ℃. Rock heterogeneity was at a low level and data dispersion was limited in our experiment. We managed to observe a clear trend of strength increase with temperature, justifying the existence of thermal strengthening in Sichuan marble. To unveil the mechanism of thermal strengthening, five factors, as predominant and comprehensive as we could concern, were investigated. After careful examination and analysis, thermal expansion was inferred to be the main reason leading to the thermal strengthening in Sichuan marble. The mechanism may lie in tighter compaction between mineral grains due to thermal expansion. Since thermal expansion is a physical process that can occur in all crystalline rocks upon heating, thermal strengthening holds a high potential to be a general property of crystalline rocks in the moderate temperature range. To our best knowledge, this study is the first to explicitly confirm the existence of thermal strengthening and comprehensively investigate the underlying mechanisms. The findings provide a new understanding of the thermal effect on rock strength, which may aid rock engineering design under a thermo-mechanical coupling working condition. Triaxial compression tests were performed on Sichuan marble specimens in the temperature range 25–200 ℃. Rock heterogeneity was at a low level and thermal strengthening in Sichuan marble was confirmed. Thermal expansion is inferred to be the leading factor of thermal strengthening in Sichuan marble after a comprehensive investigation. Triaxial compression tests were performed on Sichuan marble specimens in the temperature range 25–200 ℃. Rock heterogeneity was at a low level and thermal strengthening in Sichuan marble was confirmed. Thermal expansion is inferred to be the leading factor of thermal strengthening in Sichuan marble after a comprehensive investigation.

N. Muralidhar, K. Vadivuchezhian, V. Arumugam et al.

Natural fiber polymer composites are gaining focus as low cost and light weight composite material due to the availability and ecofriendly nature of the natural fiber. Fiber composites are widely used in civil engineering, marine and aerospace industries where dynamic loads and environmental loads persist. Dynamic analysis of these composites under different loading and environmental conditions is essential before their usage. The present study focuses on the dynamic behavior of areca nut husk reinforced epoxy composites under different loading frequencies (5 Hz, 10 Hz and 15 Hz) and different temperatures (ranging from 28 ◦ C to 120 ◦ C). The effect of loading and temperature on storage modulus, loss modulus and glass transition temperature was analyzed. Increase in storage modulus is observed with increase in loading frequency. The storage modulus decreases with increase in temperature. The glass transition temperature of the composite is determined to be 105 ◦ C. The elastic modulus calculated from the DMA data is compared with three point bending test.

Gessica Amorim, A. I. Sato, A. Souza et al.

Modern population’s needs increased demands for electricity in such a way that new energy sources were explored, in search of lower environment impacts and fossil fuels dependency. Renewable energy sources for electricity production, such as solar and wind energy, have significantly attracted attention and places as the west region of Bahia state has a good potential for its application. This location is characterized by high solar irradiance of 2136 kWh/m² a year, already having 4 photovoltaic power plants in operation and 2 more in project phases. Another possible application is the solar thermal energy and Kalina Cycle presents as a good possibility for employing it, since the non-azeotropic mixture of ammonia-water as working fluid allows low temperature heat sources utilization. Based on that, this research proposed the study of a Kalina power cycle, with steady state conditions, using thermal solar energy as low temperature heat source and applied to the solar irradiance of Bom Jesus da Lapa – BA. The thermodynamic cycle was developed and simulated with Engineering Equation Solver (EES®), thermal efficiency was analyzed by varying parameters such as: heat source temperature from 90 °C to 120 °C, high pressure line from 10 to 35 bar and ammonia mass fraction from 0.35 to 0.95. The final cycle presented a superheater before the turbine and a regenerator with poor ammonia-water mixture from the separator (as hot side) and ammonia-water mixture before entering the boiler (as cold side). Results indicated maximum efficiency of ~7.4%, with high pressure side of 35 bar, heat source temperature of 120 °C, superheater heat source temperature of 200 °C and ammonia mass fraction of 0.64 kg/kg.

Xiujuan Xie, Shaoqi Yang, Xiangdong Xu et al.

Zhiyuan Ji, Lu Sun, Luchuan Chen et al.

ABSTRACT Nanomaterials has been widely adopted in asphalt binder modification in pavement engineering. Considering the advantage of nano-Al2O3 in high-temperature resistance and chemical stability, this study investigated the feasibility of the nano-Al2O3 used in asphalt modification in terms of performances and mechanisms. The impact of the nano-Al2O3 content on modified asphalt binder’s pavement performance was analyzed via aging resistance, low temperature performance, high temperature performance, and bonding performance using various tests (e.g. DSR test, BBR test, RTFOT test, and BBS test). Results showed that the nano-Al2O3 is capable of improving base asphalt’s aging resistance, high temperature performance and bonding performance, while bringing an insignificant adverse impact on performance at low temperatures simultaneously. Moreover, modification mechanisms of the asphalt binder under the modification of nano-Al2O3 were revealed from a view of functional groups and molecular characteristics via Gel permeation chromatography (GPC) tests and Fourier transform infrared spectroscopy (FTIR) tests. According to the result, modification of base asphalt binder by nano-Al2O3 belongs to physical blended and inhibits the growth of sulfoxide groups during the aging process. Meanwhile, the nano-Al2O3 increases the base asphalt binder’s molecular weight based on LMS percentage, number-average and weight-average.

Tian Zhizheng, Han Chaoling, Chen Zhenqian

A steady-state heat transfer model of a micro-channel parallel flow loop heat pipe was established based on the distributed parameter model. Model feasibility was verified experimentally, with a maximum relative error of 10.5%. The simulation study analyzed the influences of the filling ratios and the height difference between the evaporator and the condenser on the heat transfer performance of the loop heat pipe. The results showed that the optimal filling ratios of the loop heat pipe were 80%–105.4%, and the heat transfer capacity was 1.27–1.36 kW; when the height difference between the evaporator and condenser increased from 0.4 m to 1.0 m, the heat transfer capacity increased by approximately 8.7%. The model predicted the unevenness of the evaporator flow distribution and the two-phase state inside the flat tube, improving the accuracy of the simulation results. This study can be used as a reference for the structural design of micro-channel parallel flow loop heat pipes.

W. Khan, F. Sultan, M. Ali et al.

Y. Roos

Water is an essential component of food structures and biological materials. The importance of water as a parameter affecting virion stability and inactivation has been recognized across disciplinary areas. The large number of virus species, differences in spreading, likelihood of foodborne infections, unknown infective doses, and difficulties of infective virus quantification are often limiting experimental approaches to establish accurate data required for detailed understanding of virions’ stability and inactivation kinetics in various foods. Furthermore, non-foodborne viruses, as shown by the SARS-CoV-2 (Covid-19) pandemic, may spread within the food chain. Traditional food engineering benefits from kinetic data on effects of relative humidity (RH) and temperature on virion inactivation. The stability of enteric viruses, human norovirus (HuNoV), and hepatitis A (HAV) virions in food materials and their resistance against inactivation in traditional food processing and preservation is well recognized. It appears that temperature-dependence of virus inactivation is less affected by virus strains than differences in temperature and RH sensitivity of individual virus species. Pathogenic viruses are stable at low temperatures typical of food storage conditions. A significant change in activation energy above typical protein denaturation temperatures suggests a rapid inactivation of virions. Furthermore, virus inactivation mechanisms seem to vary according to temperature. Although little is known on the effects of water on virions’ resistance during food processing and storage, dehydration, low RH conditions, and freezing stabilize virions. Enveloped virions tend to have a high stability at low RH, but low temperature and high RH may also stabilize such virions on metal and other surfaces for several days. Food engineering has contributed to significant developments in stabilization of nutrients, flavors, and sensitive components in food materials which provides a knowledge base for development of technologies to inactivate virions in foods and environment. Novel food processing, particularly high pressure processing (HPP) and cold plasma technologies, seem to provide efficient means for virion inactivation and food quality retention prior to packaging or food preservation by traditional technologies.

Tianshi Feng, Renkun Chen, Robin V. Ihnfeldt

Abstract Hydrogen (H2) is promising alternative to replace fossil fuels, but its transport and storage has been challenging. As H2 fuel cell vehicles are gaining traction, the infrastructure for storing large amounts of liquid H2 is needed. However, liquid H2 would suffer from boil-off loss, and traditional vapor compression refrigeration systems would not be able to economically recover the lost H2 due to the low efficiencies at cryogenic temperature. Magnetocaloric (MC) refrigeration systems could possess much higher coefficient of performance (COP) at cryogenic temperature compared to the vapor compression ones. Previous work on cryogenic MC systems, however, have only focused on large scale applications which use superconducting magnets to provide a large magnetic field but are prohibitively expensive to operate for small scale applications, such as that of a H2 refilling station. In this work, we modeled the performance of a MC refrigeration cycle using 1-Tesla permanent magnets for H2 liquefaction, with the objective of cooling H2 from 80 K (using liquid nitrogen as the heat sink) to 20 K (boiling point of hydrogen). We evaluated main performance metrics including the total work input to the refrigeration system, COP, total MCM mass in the system, and total volume of the permanent magnets, etc. Our modeling results indicate that such a permanent magnet-based MC cooling system is feasible for small-scale H2 liquefaction, with projected COP values significantly higher than those of vapor compression systems. This work provides design guidelines for future experimental efforts on permanent magnet MC cooling systems for cryogenic cooling.

D. Choi, S. Park, B. K. Gu et al.

Abstract Significant efforts have been applied toward fabricating three-dimensional (3D) scaffolds using 3D-bioprinting tissue engineering techniques. Gelatin has been used in 3D-bioprinting to produce designed 3D scaffolds; however, gelatin has a poor printability and is not useful for fabricating desired 3D scaffolds using 3D-bioprinting. In this study, we fabricated pore size controlled 3D gelatin scaffolds with two step 3D-bioprinting approach: a low-temperature (−10 °C) freezing step and a crosslinking process. The scaffold was crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The pore sizes of the produced 3D gelatin scaffolds were approximately 30% smaller than the sizes of the designed pore sizes. The surface morphologies and pore sizes of the 3D gelatin scaffolds were confirmed and measured using scanning electron microscopy (SEM). Human dermal fibroblasts (HDFs) were cultured on a 3D gelatin scaffold to evaluate the effect of the 3D gelatin scaffold pore size on the cell proliferation. After 14 days of culture, HDFs proliferation throughout the 3D gelatin scaffolds prepared with more than 580 μm pore size was approximately 14% higher than proliferation throughout the 3D gelatin scaffold prepared with a 435 μm pore size. These results suggested that control over the 3D gelatin scaffold pore size is important for tissue engineering scaffolds.

Ashish Kumar, M. Kaur, A. Joseph et al.

In the current investigation, an effort was made to analyze the sliding wear and friction characteristics of the surface engineered hot forming tool steel. A surface treatment technique plasma nitriding was developed onto the surface of the hot forming tool steel namely AISI H13 with a view to reduce the friction coefficients and minimize wear. The treatment was done in various N2/H2 gas mixtures for the fixed time of 24 h and at a fixed temperature of 500 ℃. The phases formed on the plasma-nitrided surface have been identified by the X-ray diffraction technique. The surface morphology of nitrided specimens and the composition of the nitride particles have been analyzed using scanning electron microscopy/energy-dispersive spectroscopy techniques. Thereafter, the untreated and treated steel specimens were chosen to slide against high strength low alloy steel (actual workpiece material) at elevated temperatures. The tests were conducted on high-temperature tribometer under the constant load of 25 N at room temperature, 200 ℃, 400 ℃, and 600 ℃. The results have shown that the average friction coefficients and specific wear rate values decrease from room temperature to 400 ℃ and again increase at 600 ℃.

Kapil Gupta Editor, Kapil Gupta

Jignesh K. Vaghela

Abstract This research involves the theoretical aspects of R134a automobile air conditioning system. The main aim of the research is to evaluate the different alternative refrigerants as a drop in substitute of R134a theoretically. For this purpose, thermodynamic properties of different alternative refrigerants i.e. R290, R600a, R407C, R410A, R404A, R152a and R1234yf are compared to R134a. Thermodynamic evaluation of standard rating cycle of vapour compression refrigeration system is carried out. Engineering equation solver and refprop soft wares have been used for the thermodynamic analysis purpose. From thermodynamic analysis, it is derived that R1234yf is best suitable alternative refrigerants as a drop in substitute of R134a. R1234yf has lower coefficient of performance as compared to R134a; however it is best suitable alternative refrigerants as a drop in substitute because it has very low global warming potential and can be substituted in the existing automobile air conditioning system with minimum modification.

Cheng Hengda, Chen Huanxin, Li Zhengfei et al.

This paper presents a fault diagnosis model based on a convolution neural network. The kernel size and number of neurons of a3-layerconvolutionnetwork were optimized by an orthogonal experiment method. The performance of the refrigerant charge fault diagnosis model of variable refrigerant flow (VRF) system was evaluated with graphed experimental data. The results show that the model established by the "data graphing & multi-layer convolutional network" method can be effectively used for the refrigerant charge fault diagnosis of the VRF system. With 20 chosen input features, the accuracy of the 9 level refrigerant charge fault diagnosis reached 91%,surpassing the performance of traditional back propagation neural networks(BPNN).This is the first time to achieve VRF system refrigerant charge fault diagnosis by using a convolutional network, laying a foundation for the expansion of related research.