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Dilution refrigerators are widely used in the fields of condensed matter physics and quantum technology. The condensation-driven dilution refrigerator uses a condenser operating at temperatures below the Still to liquefy the 3He vapor and achieve the circulation of 3He, which has the advantages of compact structure, lightweight, low cost, and low vibration. The published research primarily focuses on the system architecture and performance, and the research and analysis on the thermodynamic cycle are still incomplete. In this paper, the condensation-driven dilution refrigeration cycle has been clarified as a thermally driven refrigeration cycle, and the thermodynamic performances including the figure of merit and thermodynamic perfectibility are investigated. Optimizations have been made to the key components of the previous prototype, and the lowest no-load temperature of 68 mK and a cooling power of 4 μW at 100 mK were achieved. Compared with the previous prototype, the thermodynamic perfectibility of the system increased from 7.63% to 17.83%. The impact of the Still heating strategies on the system was analyzed, and a start-up strategy was proposed to speed up the cooldown process. [ABSTRACT FROM AUTHOR]

We investigate quantum non-equilibrium refrigerators with one- and two-qubit systems in a squeezed thermal bath. We characterise their performances in the presence of squeezed heat baths, in terms of their coefficients of performance, cooling rates and figures of merit. Our results show that the performance of the refrigerators is strongly influenced by the squeezing parameter and the number of qubits. The performance of the two-qubit refrigerator (TQR) is found to be better than that of the one-qubit refrigerator (OQR) under the same operating conditions. Our findings suggest that a squeezed thermal bath can be a promising resource for the design of efficient quantum refrigerators in the non-equilibrium regime. [ABSTRACT FROM AUTHOR]

• Developed a dynamic model of a triple-evaporator domestic refrigerator/freezer. • Dynamic model validated within a 2 % deviation in average power consumption. • Implemented a two-stage economized cycle and its control scheme. • Achieved 12.9 % and 80 kWh/year reduction in power and energy consumption, respectively. • Estimated 18 TWh/year in global energy savings by 2030 with 10 % market penetration. Domestic refrigerator/freezers account for approximately 6 % of all energy consumption around the globe and mainly rely on vapor compression cycles to operate. Researchers have investigated alternative cycle architectures such as dual-loop cycles and parallel circuit cycles to improve their efficiencies. Despite the demonstrated energy saving potential of these advanced cycles, additional implementation costs are often not justifiable. However, to meet forthcoming stricter energy standards while ensuring flexible multi-temperature operation of domestic refrigerator/freezers, advanced cycle architectures are needed. In this paper, a state-of-the-art bypass circuit cycle triple-evaporator domestic refrigerator freezer with R-600a and a reciprocating compressor has been used as the baseline cycle investigate an alternative cycle configuration. Specifically, this work presents a two-stage vapor-injected cycle with a multi-evaporator system to enable energy savings and cost-effectiveness. The cycle establishes two separate evaporation temperatures to better match the cabinet temperature of fresh food and freezer compartment. The reduced difference between cabinet temperature and its evaporation temperature decreases the irreversibilities in the heat exchanger and improves overall system efficiency. Moreover, the addition of the economization line from the medium temperature evaporator reduces the compressor work. To capture the complex transient behavior of both the baseline system and proposed cycle architecture with their control strategies, a dynamic model has been developed and validated with experimental data. The validated dynamic model with the baseline cycle was modified to consider the two-stage vapor-injected cycle and its control logic, and simulation results yielded up to 13 % energy consumption reduction with respect to the baseline system. [ABSTRACT FROM AUTHOR]

Improving the performance of drop-in hydrocarbon refrigerants for the increasing in-flow of conventional refrigerators to Nigeria is a necessary sustainable strategy. This experimental study investigates the enhancement limits of a liquid-line magnetic field, CNT nano-lubricant, and a combination of both on an R134a domestic refrigerator with 40–70 g each of R600a refrigerants. The study compares the performance of R600a refrigerant without enhancements (pure) and with two pairs of 3000 Gauss liquid-line mounted O-ring permanent magnets (Mag), 0.2 g L−1 concentration of CNT nano-lubricant (Nano), and both liquid-line magnet and CNT nano-lubricant (Mag-Nano). Test parameters include evaporator air temperature, discharge pressure, power consumption, coefficient of performance (COP), and total equivalent warming impact (TEWI). The results show that enhancement methods led to higher COP in the range of 16.64–42.38%. At the same time, evaporator air temperature, discharge pressure, power consumption, and TEWI were lower by 9.76% to 20.96%, 17.75% to 34.26%, 5.22% to 13.42%, and 5.88% to 10.86%, respectively. In conclusion, the proposed enhancement techniques in the refrigeration system provide normal, safe, and efficient operation. [ABSTRACT FROM AUTHOR]

The cooling capacity of a typical dilution refrigerator is mainly determined by the circulating flow of the He-3 in the system, which is usually realized by the external circulation pump. In order to increase the concentration of circulating He-3, the still often take the orifice structure to limit the influence of the superfluid helium film, and this structure will also have a certain impact on the flow rate of He-3. This paper summarizes the flow rate models of each part of the orifice structure, and establishes a model related to the influence of pumping speed and the diameter of orifice on the flow rate of circulating He-3. The relationship between pumping speed and flow rate is developed and the relation is divided into three phases for detailed analysis. It is found that the flow rate and the concentration of circulating He-3 increase first and then decrease with the increasing diameter of orifice at a certain pumping speed, and the possible reasons for this phenomenon are analyzed. The results indicate that there is an optimal orifice diameter at a determined pumping speed. [ABSTRACT FROM AUTHOR]

• Displacer type pulse tube refrigerator with inertance tube or orifice is tested. • Efficiency of single-stage refrigerator can be improved by adding inertance tube. • The lowest temperature decreases of two-stage refrigerator from 18.9 K to 15.6 K. Displacer type pulse tube refrigerator (DPTR) can get high efficiency with strong phase shifting and acoustic work recovery to advantages. However, the optimal match of gas driving displacer can only be reached at one point, while the linear motor driving displacer has a complex structure. And for two-stage DPTR, more parameters need to be optimized such as step ratio. A well-matched displacer costs a lot and asks high quality manufacturing. In this work, an orifice and an inertance tube were added to the single-stage DPTR and two-stage DPTR as an additional adjustment parameter. For single stage DPTR, the experimental results indicate that the lowest temperature decreases from 44.7 K to 42.1 K after a suitable inertance tube was added. The cooling power can be increased with almost same efficiency by adding an orifice with appropriate opening turn. After adding an additional inertance tube of the two-stage DPTR, the lowest temperature of 15.6 K was achieved, while the lowest temperature of 15.7 K was achieved by installing an orifice to the two-stage DPTR. [ABSTRACT FROM AUTHOR]

Copyright of Revista Foco (Interdisciplinary Studies Journal) is the property of Revista Foco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 mK, with a minimum temperature of 7.6 mK and a cooling power of 450 μW at 100 mK. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information. [ABSTRACT FROM AUTHOR]

Unstable flow in a pump-turbine can cause pressure pulsation, and the resulting vibration deteriorates the stability and operating safety of the unit. This study conducted three-dimensional numerical calculations of the overall flow passage of a pump-turbine with splitter blades under the small guide vane opening, and the unsteady flow characteristics of the turbine were investigated. The results showed that the pressure fluctuation was more severe at lower head operating conditions with lower efficiency, especially in the vaneless area (the runner blade passages). Under the lower head condition, the proportion of 12 times the rotational frequency (12 f/fn) increased in the vaneless area, and the amplitude of 1 f/fn as well as 2 f/fn became larger in the runner blade channel, with more space occupied by vortices and reflux areas. A spiral vortex rope formed in the draft tube, increasing the proportion of 0.4 f/fn and 0.7 f/fn pressure pulses. [ABSTRACT FROM AUTHOR]

Achieving fast and precise initialization of qubits is a critical requirement for the successful operation of quantum computers. The combination of engineered environments with all-microwave techniques has recently emerged as a promising approach for the reset of superconducting quantum devices. In this work, we experimentally demonstrate the utilization of a single-junction quantum-circuit refrigerator (QCR) for an expeditious removal of several excitations from a transmon qubit. The QCR is indirectly coupled to the transmon through a resonator in the dispersive regime, constituting a carefully engineered environmental spectrum for the transmon. Using single-shot readout, we observe excitation stabilization times down to roughly 500 ns, a 20-fold speedup with QCR and a simultaneous two-tone drive addressing the e–f and f0–g1 transitions of the system. Our results are obtained at a 48-mK fridge temperature and without postselection, fully capturing the advantage of the protocol for the short-time dynamics and the drive-induced detrimental asymptotic behavior in the presence of relatively hot other baths of the transmon. We validate our results with a detailed Liouvillian model truncated up to the three-excitation subspace, from which we estimate the performance of the protocol in optimized scenarios, such as cold transmon baths and fine-tuned driving frequencies. These results pave the way for optimized reset of quantum-electric devices using engineered environments and for dissipation-engineered state preparation. [ABSTRACT FROM AUTHOR]

With the improvement of the national economic level and the diversity of medical equipment needs, the car refrigerator as an important carrier in the cold chain logistics link is rapidly developed. According to the different applications, there are differences in the refrigeration technologies and cooling capacity of car refrigerators. Around car refrigerators, the development status of car refrigerator refrigeration technologies is reviewed, the characteristics and functions of car refrigerators are introduced, the mechanism and characteristics of several refrigeration technologies under different scenarios are studied, and the potential development and application directions of car refrigerators with different refrigeration technologies are summarized. The research results are of certain practical significance to the improvement of the last-mile of cold chain logistics. [ABSTRACT FROM AUTHOR]

Background: This study was carried out to evaluate the quality changes and storage stability of fish muscle (Pangasianodon hypothalamus) preserved in fabricated portable solar cooler and domestic refrigerator. Methods: Fish muscle from Pangasianodon hypothalamus were studied, keeping it in a fabricated portable solar cooler and in a domestic refrigerator at 5°±1°C to compare the shelf-life and quality of fish muscles. The fish muscle was packed separately in LDPE (low density polyethylene) packets and stored in a solar cooler and domestic refrigerator up to 7 days to compare the different physicochemical, microbiological and sensory parameters on 0, 3rd and 7th day. Result: The results revealed that there were non-significant changes (P>0.05) observed for different parameters during the storage periods in both solar cooler and domestic refrigerator. In contrast to the domestic refrigerator requiring electricity for functioning, solar cooler requires green energy for the same which is abundant and free of cost, thus justifying its economical sustainability. Finally, from the present study it was concluded that the preservation of fish in a portable solar cooler system is thus economically suitable, feasible and acceptable up to 7 days as compared to domestic refrigeration method at controlled temperature. [ABSTRACT FROM AUTHOR]

• A dual-temperature zone refrigerator driven by VI linear compressor is proposed. • A numerical model of VI linear compressor is established and validated. • The refrigeration characteristics of the compressor and system are analyzed. • The modulating strategy of VI compressor for refrigeration is proposed. • The effects of key parameters on the refrigeration characteristics are investigated. The vapor injection linear compressor exhibits a distinctive mass flowrate distribution characteristic compared to other vapor injection compressors, making it promising for application in dual-temperature zones refrigerating systems. In this study, a novel system of dual-temperature zone refrigerators featuring two parallel evaporators is proposed, and numerical models of the vapor injection linear compressor and its system are established, and then validated by experimental results. Theoretical analysis is conducted to explore the cooling performance and capacity-modulating characteristics of the system. Compared to traditional refrigeration systems, the vapor injection of medium-pressure refrigerant enhances the cooling capacity and performance at a large piston stroke while deteriorating the freezing capacity at a small piston stroke. This system offers the flexibility of adjusting the cooling ratio by modulating supply voltage and driving frequency to meet the cooling requirements. Correspondingly, special control strategies for this kind of system for the best performance are proposed in this study. Additionally, the structural parameters significantly influence the cooling performance: a larger injection area and a smaller distance to the top death center prove to be more advantageous for overall cooling performance. This research provides valuable insights for optimizing the structural parameters and control strategies, serving as a beneficial reference for future innovative refrigeration technologies. [ABSTRACT FROM AUTHOR]

It is the refrigerator that is frequently used in homes. Freezing and refrigerating temperature sensors are significant temperature-sensing components in the refrigerator. However, it is simple to insert the temperature sensor wires erroneously during the manufacturing process. Currently, there is no effective method to detect the correctness of the wiring harnesses. We propose a novel detection method that combines machine vision and resistance analysis for the wiring harnesses of refrigerator temperature sensors. We utilized machine vision technology to determine the color and insertion position of each wire in the wiring harnesses. We distinguish the types of sensors by analyzing the resistance range of the temperature sensors. We combine two approaches to detect the wiring harnesses connecting the temperature sensors. The experimental results demonstrate that the proposed method can effectively detect the correctness of the wiring harnesses connecting the temperature sensors, and the accuracy reaches 99.19%. The proposed method has a good generalization in other electrical wiring harness detection problems. [ABSTRACT FROM AUTHOR]

The process of phasing out of medium and high global warming potential refrigerants is accelerating in all areas of refrigeration, particularly since the European F-Gas Regulation No. 517/2014 and the ensuing Kigali amendment went into effect. Hydrocarbon refrigerants are being considered as suitable alternatives due to their low global warming potential and excellent thermal properties, but due to their flammability, safety precautions must be followed. This theoretical study contributes to the evaluation of the thermal and environmental impact of hydrocarbon refrigerants as drop-in alternatives to R134a in domestic refrigerator. In order to conduct an analysis of energy, exergy, and environmental factors, R134a and all hydrocarbons refrigerants proposed by ASHRAE--R290, R600, R600a, R601, R601a, and R1270--were examined as operating fluids used in a domestic refrigerator with a cooling capacity of 157 W and constant condenser temperature of 40°C and variable evaporator temperature every 5°C between -5 and -30°C. The results revealed that all the alternative refrigerants except R601 and R601a have higher thermal and environmental performance than R134a and can be used after refrigerator compressor replacement. [ABSTRACT FROM AUTHOR]

Maintaining adequate temperatures for preserving food in a domestic refrigerator is a task that is affected by several factors, including the daily use of the appliance. In this sense, this work presents the development of a novel control system based on fuzzy logic that considers usage habits such as the amount of food entering the refrigerator and the frequency of opening doors. Thus, the control comprises input variables corresponding to the internal temperatures of both compartments, the thermal load entered, and the refrigerator door-opening signal. By simulating the usage habits of a refrigerator with a variable-speed compressor, the control performance was evaluated. The results showed that implementing fuzzy control using usage habits was robust enough to maintain adequate thermal conditions within the compartments and a lower thermal fluctuation concerning the reference control of the refrigerator (factory control). In terms of energy, the fuzzy control resulted in an energy saving of 3.20% with the refrigerator empty (without thermal load) compared to the reference control. On the other hand, the individual integration of the thermal load in the fuzzy control resulted in 2.08% energy savings and 5.45% for the integration of the thermal load compared to the reference control. Finally, considering the combination of usage habits, the fuzzy control presented a higher energy consumption than the reference control, around 9.7%. In this case, the fuzzy control maintained more favorable thermal conditions in both compartments, whereas the reference control presented a warmer thermal condition in the freezer. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of sodium laureth sulfate (SLES) on the wettability of the surface of the two most common recycled plastics in refrigeration equipment: HIPS (high-impact polystyrene) and ABS (acrylonitrile–butadiene–styrene). These plastics, in the form of flakes, were identified on the basis of their FTIR spectra, and then, they were subjected to a study of contact angles using the sessile droplet method. The solutions for the angle analysis included tap water with the addition of SLES. The results of this study showed that at SLES concentrations of 0.1 g/L and 0.2 g/L, the differences in the contact angles for HIPS and ABS were 10.76° and 10.10°, respectively. This research confirmed the potential of using SLES as a support for the flotation separation of plastics with similar densities and surface characteristics, such as HIPS and ABS. [ABSTRACT FROM AUTHOR]

We propose a model of two identical autonomous quantum refrigerators that interact through their qubits coupled to cold thermal baths. We consider the same specific disposition for each refrigerator related to a three-level system coupled to different thermal baths and, in turn, to a qubit as the object to be cooled. By coupling the two systems, we show that under certain conditions on the model parameters, the devices can operate in the regime of an independent autonomous quantum refrigerator or be subject to an adjustment of the thermodynamic performances. We further investigate the correlations induced by the interaction between the two refrigerators, and illustrate their behavior with respect to their thermodynamic performances. We have found that adjusting the different interaction constants of the model can lead to an evolution of the quantum correlations of the two machines that is inversely related to the behavior of the thermodynamic quantities of both refrigerators. However, this is not necessarily the case when the temperatures of the model are considered as the reference parameters. [ABSTRACT FROM AUTHOR]

• Preliminary exploration of radial wave rotors in refrigeration applications. • Radial configuration simplifies refrigeration cycle. • Two strategies are posited to augment equipment adaptability. • The dynamics of radial heat transfer and power consumption have been investigated. • The refrigeration coefficient peaks when φ = φ i and n = 2750 rpm. Gas wave refrigeration technology is an innovative refrigeration technique that harnesses pressure waves to facilitate energy exchange. In this paper, the wave rotor undergoes a transformation from its original axial structure to a radial structure. The self-pressurization capability of radial structure is proven to facilitate autonomous gas circulation, obviating the necessity for a drive fan, according to numerical simulations. We explore two methods to regulate the cycling ability for improved adaptability: altering exhaust ports and controlling exhaust resistance. The former offers a broader range of adjustment, while the latter is suitable for fine-tuning due to associated throttling pressure loss. Additionally, the mechanism of radial heat transfer is probed, revealing its intensification correlating with rising rotational speeds. The study also delves into the power consumption dynamics unique to the radial configuration. Influenced by these two factors, the device attains its peak efficiency near the specific internal circulation state of φ = φ i. The optimal rotational speed is determined to be 2750 rpm, which offers a balance between eddy current loss and power consumption. This study demonstrates that a radial gas wave refrigerator enables the integration of the pressurization and refrigeration processes. It serves as the foundation for subsequent structural optimization and experimental research on radial configurations. [ABSTRACT FROM AUTHOR]

High-intensity heavy-ion accelerator facility (HIAF) is an accelerator-driven high-current heavy ion facility, currently under construction in Guangdong, China. The proton linear accelerator of HIAF linac has 96 superconducting cavities and 17 cryomodules cooled by 2 K saturated superfluid helium. Cryogenic tests should be carried out in a test cryogenic system prior to the online operation of each cavity and cryomodule. The cryogenic distribution system (CDS) is the main part of the test cryogenic system, which is used for transporting cryogenic fluid between helium refrigerator and test terminals. A specific CDS is developed due to the long cryogenic test time. Each test terminal can be independently cooled and heated up, saving quite a bit of time without impacting the others. This article provides comprehensive explanations for the process design, process analysis, and special structure design which enhance the system's maintainability. Furthermore, particular technical designs, such as measuring system, helium guard, and elimination of thermoacoustic oscillations, are described in detail. [ABSTRACT FROM AUTHOR]

Pulse tube refrigerators are a critical enabling technology for many disciplines that require low temperatures. These refrigerators dominate the total power consumption of most modern cryostats, including those that reach millikelvin temperatures using additional cooling stages. In state-of-the-art commercial pulse tube refrigerators, the acoustic coupling between the driving compressor and the refrigerator is fixed and optimized for operation at base temperature. We show that this optimization is incorrect during the cooldown process, which results in wasted power consumption by the compressor and slow cooldown speed. After developing analytic expressions that demonstrate the need for acoustic tuning as a function of temperature, we dynamically optimize the acoustics of a commercial pulse tube refrigerator and show that the cooldown speed can be increased to 1.7 to 3.5 times the original value. Acoustic power measurements show that loss mechanism(s)—and not the capacity of the compressor—limit the maximum cooling available at high temperatures, suggesting that even faster cooldown speeds can be achieved in the future. This work has implications for the accessibility of cryogenic temperatures and the cadence of research in many disciplines such as quantum computing. Pulse tube refrigerators are a critical enabling technology for many disciplines that require low temperatures, including quantum computing. Here, the authors show that dynamically optimizing the acoustic parameters of the refrigerator can improve conventional cooldown speeds up to 3.5 times. [ABSTRACT FROM AUTHOR]

Compact heat-driven cryocoolers can harness the thermal energy produced by burning a small quantity of natural gas to accomplish liquefaction. This addresses the requirements of distributed natural gas stations in remote locations. This paper introduces a Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler designed for natural gas liquefaction. It conducts a comparative analysis of the mechanical and electrical systems, focusing on the acoustic field, available energy loss, and performance. Simulation results indicate that the optimized mechanical configuration system achieves peak performance with a piston area ratio of 0.84 and a piston phase angle of 90°. It yields a cooling power of 1964 W@130 K when driven by an 873 K heat source, resulting in an overall system efficiency of 28.3%. This marks a notable enhancement compared to current thermoacoustic systems. While the electrical configuration provides superior stability, the performance is constrained by significant losses in acoustic-electric conversion of linear alternators and compressors. To further enhance efficiency, it is worthwhile to establish direct power transfer between the pistons, for example, by aligning the expansion piston and compression piston coaxially. The evolved duplex configuration eliminates the loss from electrical energy conversion, leading to a remarkable 64.7% increase in overall efficiency. Simultaneously, this evolutionary approach offers a new perspective to elucidate the inherent connections among Stirling heat engines of Franchot double-acting and duplex. It provides valuable theoretical insights for the subsequent analysis and design of Stirling heat-driven refrigerators or cryocoolers. • A Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler is proposed. • A notable enhancement compared to current thermoacoustic systems. • The electrical configuration provides stability but limited by energy conversion losses. • The evolved duplex configuration eliminates the loss of energy conversion. [ABSTRACT FROM AUTHOR]

A refrigerated system experimental bench using R404A as the refrigerant was built to address the current issues of high compressor discharge temperature and poor refrigeration performance of refrigerated systems for cold storage. The effects of compressor speed and temperature changes within the storage on the main refrigeration performance parameters of the system were studied and analyzed. The results show that when the rotational speed is increased from 2500-4500 rpm under the conditions of 32 °C outside and 0 °C inside, the highest system exhaust temperature is 84.3 °C, which is lower than 90 °C, and the maximum system COP is 3.86, and when the compressor speed is increased from 3500 rpm under the conditions of -5 °C to 5 °C, the system exhaust temperature is lower than 90 °C. The COP can reach 2.74, especially at -5 °C. [ABSTRACT FROM AUTHOR]

Effective and efficient energy consumption, environmental sensitivities, climate change, and global warming are significant issues that the world is currently focusing on. Industrial refrigerators are the devices that have significant effects under the mentioned headings. Environmental sensitivities should be valued when improving innovative designs for effective and efficient energy consumption in industrial refrigerators. Moreover, with both international and national regulations recently, designs to be made at this point have become an obligation rather than a necessity. This study aims to use energy effectively and efficiently, creating an energy efficiency factor in industrial refrigerators; various aspects, such as components, insulation, refrigerant, control technique, ambient conditions, cooling cycle, and airflow were studied from different perspectives and grouped, and the outputs obtained as a result of the studies were compiled. The grouped and compiled outputs were presented title-based and optimum solutions in terms of energy efficiency were discussed. The presented outputs will be used as effective design inputs in the studies carried out by researchers and product manufacturers, thus, as a result of innovative studies that create energy efficiency, designs with substantial environmental sensitivity, especially carbon emissions, will emerge. In addition, it thought that innovative and efficient designs would make direct and indirect contributions to the economy. [ABSTRACT FROM AUTHOR]

Low-temperature scanning probe microscopes (SPMs) are critical for the study of quantum materials and quantum information science. Due to the rising costs of helium, cryogen-free cryostats have become increasingly desirable. However, they typically suffer from comparatively worse vibrations than cryogen-based systems, necessitating the understanding and mitigation of vibrations for SPM applications. Here we demonstrate the construction of two cryogen-free dilution refrigerator SPMs with minimal modifications to the factory default and we systematically characterize their vibrational performance. We measure the absolute vibrations at the microscope stage with geophones and use both microwave impedance microscopy and a scanning single-electron transistor to independently measure tip-sample vibrations. Additionally, we implement customized filtering and thermal anchoring schemes and characterize the cooling power at the scanning stage and the tip electron temperature. This work serves as a reference to researchers interested in cryogen-free SPMs, as such characterization is not standardized in the literature or available from manufacturers. [ABSTRACT FROM AUTHOR]

Capillary tubes, as the expansion devices in refrigerators, are unable to actively match cooling capacity and load, which will increase the energy consumption. Moreover, due to the limitations of miniature valve needle machining accuracy and structural strength, orifice-type EEVs are not suitable for low mass flow rate in refrigerators. A novel rotary-baffle curved-channel electronic expansion valve (RBCC-EEV) is proposed to replace capillary tube to achieve flow regulation in household refrigerators. Based on the special structure and regulation principle of RBCC-EEV, characteristics of mass flow rate and cavitation are studied experimentally and numerically, respectively. Experimental results show that, as opening ratio (OR) increases, the synchronous changes in the inlet area and length of the curved channel lead to a super-linear variation in mass flow rate, with increase rate growth from 0.018 kg h−1 OR−1 to 0.061 kg h−1 OR−1. Numerical results show that, under centrifugal forces, the pressure difference along the normal direction of the streamline leads to the differences in degree of cavitation, which is called asymmetric cavitation phenomenon. In addition, under the influence of this phenomenon, the prematurely cavitation of refrigerant near the inside surface will block the inlet of curved channel early, resulting in a 3.4 % decrease in mass flow rate. [ABSTRACT FROM AUTHOR]

• The presence of frost on the evaporator coil degrades the cooling performance. • K-means image segmentation-based frost detection and thickness estimation is proposed. • Frost thickness was estimated using image analysis with an error of 13.69%. • Results were compared with conventional sensors and existing image processing methods. • The method can serve as a reliable feedback source for efficient defrosting. Frost accumulation is a common problem when moisture in the air condenses and freezes on surfaces like heat exchange tubes of refrigeration units. Frost accumulation negatively impacts heat exchange by disrupting the process, reducing system efficiency, and causing operational issues. Therefore, defrosting is mandatory to maintain the rated performance; however, modern automatic defrosting systems rely on sophisticated sensors for frost quantification. These sensors are susceptible to degraded performance with the passage of time under varying environmental conditions. To this end, we introduce a robust and generic image processing-based solution that relies on building a data-driven regression-based model for frost detection and thickness estimation. We evaluated the effectiveness of the proposed method on a newly collected dataset with encouraging performance in terms of a low error margin of 13.69% when compared to conventional capacitive and photoelectric sensors-based frost thickness estimation with error margins of 15.17% and 17.5%, respectively. Similarly, other image processing-based methods, such as Global thresholding, Adaptive mean, and Adaptive gaussian thresholding for segmentation, were compared with the proposed method. Deviations in the error margins were found to be 19.94%, 28.96%, and 27.85%, respectively. These findings highlight the appropriateness of employing K-means for estimating frost thickness. [ABSTRACT FROM AUTHOR]

This study proposes using the Light Gradient Boosting Machine (LightGBM) to improve the defrosting control strategy in frost-free refrigerators. By analyzing data and optimizing control parameters, the aim is to enhance defrosting performance and reduce energy consumption using the time–temperature difference (t–dT) approach. The research involves analyzing performance and reliability data for two control strategies (time–temperature (t–T) and t–dT), creating three feature sets (FS1, FS2, and FS3) based on correlation analysis, and employing LightGBM models to forecast datasets. The control parameter threshold (Δ T op,s) is optimized using the LightGBM-based data. The key findings indicate that the t–dT strategy with a fixed threshold (7.8 °C) outperforms the t–T method in efficiency at an ambient temperature of 38 °C. At 10 °C, the performance tests show no significant difference, but the t–T method performs better in reliability tests. The FS1-based data from the t–dT strategy in the reliability test at 10 °C are considered ideal input, and the LightGBM models generate FS2-based and FS3-based data for evaluation. The optimized t–dT defrosting strategy achieves favorable refrigeration conditions with minimal power consumption and optimal cooling capacity. The ideal Δ T op,s threshold, based on data for the idealized frosting condition, is determined to be 8.3 °C. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Donghua University (English Edition) is the property of Journal of Donghua University Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Superconducting electric motors are required in order to deliver lower-carbon aviation. Critical to the success and viability of operating superconducting electric motors in aviation is keeping the superconducting coils at their operating temperature. This paper examines the challenges of keeping a superconducting motor cold if it were used on a single aisle passenger aircraft such as an Airbus A320. The cooling problem is defined and different cooling scenarios are investigated to determine viability. The investigation has shown that for a motor with a superconducting rotor only (copper stator), a Stirling-type cryocooler would be sufficient. However, if the motor is to be fully superconducting, then the cooling loads of the stator, which are much higher, make mechanical refrigeration impractical and the only option is to cool the motor with the heat sink of a liquid hydrogen fuel. [ABSTRACT FROM AUTHOR]

• Room-temperature magnetocaloric refrigeration prototype with helium as the heat transfer fluid and packed particle Gd 0.8875 Ce 0.1025 Si 0.84 Cr 0.19 as the refrigerant. • Measurements on temperature spans and cooling power with three particle sizes at two different operating cycles. • Reduction of performance in large particles from insufficient thermal diffusion in faster cycle. • Validated numerical model and compared effects of viscous dissipation and thermal diffusion. • Implications of magnetocaloric refrigerant with low thermal diffusivity for cryogenic temperatures discussed. Magnetocaloric refrigeration has strong potential towards achieving high efficiency hydrogen liquefaction. Optimising parameters such as particle size and operating cycles can have a significant impact on liquefaction performance. This work reports on a room temperature magnetocaloric refrigeration prototype designed with helium as the heat transfer fluid and packed particle Gd 0.8875 Ce 0.1025 Si 0.84 Cr 0.19 as the refrigerant. The temperature spans and cooling power with three different particle sizes at two different operating cycles were measured. A maximum temperature span of 16.7 K and a maximum cooling power of 8.6 W kg−1 were obtained. Reduction of performance in the faster cycle was observed in larger particles due to insufficient thermal diffusion time and its implications for cryogenic temperatures are discussed. A numerical model was developed based on the experimentally observed variation of the temperature span and cooling power with particle size and cycle duration. This model was then used to study the competing effects of viscous dissipation and thermal diffusion for different particle sizes and cycle durations. [ABSTRACT FROM AUTHOR]

• Innovative passive cooling system to reduce refrigerator energy consumptions. • Use of external air for condenser cooling enables a lower temperature heat source. • The heat from the condenser drives natural airflow circulation of the external air. • CFD analysis optimize device geometry and heat transfer. • Experimental test demonstrates significant energy savings of 36.0 % ± 5.2 %. The paper presents a solution aimed at enhancing the cooling efficiency of domestic refrigerators. The proposed approach involves a passive cooling system designed to leverage the colder external air during winter for the cooling of the fridge condenser. Indeed, the use of a colder external source helps to increase the efficiency of the refrigerator. The system provides a connection between the rear section of the refrigerator and the external environment via two ducts. The heat dissipated by the condenser induces the natural circulation of outdoor cooling air. The study includes experimental and CFD analysis. The experimental results shows that the configuration with the cooling system achieves higher useful effects and lower power consumption compared to the traditional setup, yielding a reduction in energy consumption of 36.0 % ± 5.2 % when operating with an external air temperature of 0 °C. The CFD model is validated through experimental data, and simulations are conducted to optimize the sizing and design of the system components. Parametric analysis indicates that duct diameters of 12 cm and a box depth of 15 cm behind the fridge are required to optimize heat transfer and aid natural circulation. In summary, the paper offers a suitable solution to increase the fridge efficiency in cold climatic locations. [ABSTRACT FROM AUTHOR]

Liquid hydrogen has more advantages than gaseous hydrogen in terms of economy and convenience of storage and transportation owing to its higher energy density. Therefore, the hydrogen liquefaction technology is conducive to promotion and application for hydrogen energy in many sectors. The small-scale regenerative refrigerators usually use helium as the working fluid, which is of the high-low temperature cycle, and bring about a significant entropy generation during the cooling process. In this work, the study on the liquefaction rate and FOM (figure of merit) is implemented with a working fluid of hydrogen. It shows that the entropy generation much decreases when applying the distributed refrigeration method comparing to the high-low temperature cycle, and the COP (coefficient of performance) reaches 80 % when cooling the sensible heat load and conversion heat. The calculation results indicate that the liquefaction rate of the temperature-distributed cycle reaches 34.32 L/d at a refrigeration power of 15 W (a representative case). While the maximum of FOM is 0.483, which is improved by 21.7 % compared with the high-low temperature cycle. • H 2 liquefaction rate is calculated with the distributed method for the first time. • The entropy generation much decreases when applying this method. • The liquefaction rate of hydrogen is improved by increasing pressure. • FOM is greatly improved by 21.7 % compared with the high-low temperature cycle. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of n-butane (R600) and isobutane (R600a) flows in adiabatic capillary tubes. In total, 48 experimental data points were gathered spanning the typical conditions of household refrigerators, with capillary inner diameters ranging from 0.53 to 0.79 mm, tube lengths ranging from 2.5 to 3.5 m, inlet pressure ranging from 2.83 to 6.05 bar, exit pressure ranging from 0.3 to 0.9 bar, inlet subcooling ranging from 4.7 to 15.2 °C, and mass flow rates ranging from 0.53 to 2.95 kg h−1. In addition, the accuracy of π-type correlations priorly developed for R600a flows was verified when used with R600 to predict the refrigerant mass flow rate. Also, it was found the mass flow rate predictions of the algebraic model developed by Hermes et al. (2010) for R600a agreed well with the R600 experimental data, with more than 90 % of data points within ± 10 % error bands. [ABSTRACT FROM AUTHOR]

Temperature uniformity and temperature fluctuation are two important parameters of refrigerator and have significant effects on fresh-keeping and cold-storage technology. The influencing factors of temperature distribution attract more attention in refrigerator factory. However, the definitions of temperature uniformity and temperature fluctuation are still ambiguous, and present characterization methods cannot accurately describe the temperature field of refrigerator. This paper proposed a novel dual characterization method to reveal the temperature uniformity and fluctuation (TUF) and presented a new arrangement strategy of temperature measuring elements in refrigerator. Results show the proposed method can simultaneously and visibly characterize the TUF behavior. The slope and area of curves in temperature radar chart reveal the TUF distribution clearly. The first layer of refrigerator shows a greater temperature fluctuation, especially when the compressor is working. Refrigerators with different volume have different TUF phenomena. Adding a cold storage module on the top of refrigerator can notably improve TUF feature and make the internal temperature closer to target temperature. The mechanism of TUF change was discussed from heat transfer and cascaded energy utilization. The proposed dual characterization method can reveal temperature distribution with space and time simultaneously and help improve the temperature field of cold-heat preservation to save energy. • Propose the new methodology of temperature fluctuation and temperature uniformity. • Reveal temperature fluctuation and uniformity visually by the sharpness and enclosed area of curve in temperature radar chart. • Present a 27-point strategy to measure temperature field of refrigerator accurately. • Improve the temperature fluctuation and uniformity of refrigerator by 20%∼75% through adding a cold storage module. [ABSTRACT FROM AUTHOR]

Developing high-efficiency and environmentally friendly cooling technology is crucial for sustainable life. Heat-driven thermoacoustic refrigerator (HDTR) is an emerging cooling technology characterized by no moving components, eco-friendly working substances, and high reliability. This study reports an innovative efficient HDTR with bypass configuration, which employs eco-friendly and economical working substances, the nitrogen and water. The bypass configuration enables good matching of acoustic power between the engine and cooler units at high heating temperatures, thus enhancing the efficiency. In addition, the employment of liquid resonator significantly reduces the working frequency and reduces the loss. An experimental investigation is performed on the onset characteristics and operating performance of the proposed system. The results show that a highest coefficient of performance (COP) of 0.49 and a cooling power of 726 W are achieved at the heating, ambient, and cooling temperatures of 500, 35, and 7 °C, respectively, exhibiting a high level for the HDTRs employing nitrogen. This work supplies an effective way to the efficiency enhancement of the HDTRs, indicating substantial potential of the proposed HDTR in eco-friendly air-conditioning applications. [ABSTRACT FROM AUTHOR]

Refrigeration has become an integral part of our daily lives and can be regarded as a process whose replacement is nearly impossible. Therefore, the only way of making this process efficient is by reducing the energy consumed by the components of refrigerators. One way of doing this is to reduce the power consumption of compressor by the addition of nanoparticles either in a refrigerant or in a lubricant. This study focusses on producing nanolubricant (Al2O3/Synthetic lubricant) and dispersing the nanolubricant into R-134a compressor. This study investigates that how much power can be reduced when Aluminum oxide (Al2O3) nanoparticles dispersed in SL-32 lubricant (base fluid). A comparison between SL-32 lubricant with and without the addition of Aluminum oxide nanoparticles was done and it showed a reduction of 0.913% in current consumption and 2.74% in power at the same initial temperature of 31°C in both cases. Hence it can be concluded that Alumina nanoparticles can be utilized to reduce the energy utilized by compressors by creating a nanolubricant with SL-32 lubricant. [ABSTRACT FROM AUTHOR]

E-waste is a valuable secondary resource containing numerous toxic substances and high-value components. If improperly handled, it will cause severe environmental pollution. Therefore, efficient recycling of this material can reduce environmental pollution. However, after crushing, fine crushing, and magnetic separation, a substantial quantity of fragmented non-magnetic materials with high value, such as copper andg aluminum, remain. Refrigerators, as typical e-waste, have a similar composition to fragmented non-magnetic materials. Consequently, this paper focuses on the issues of low efficiency, environmental pollution, and resource waste in sorting fragmented non-magnetic materials from waste refrigerators. This paper constructs a data set of fragmented non-magnetic materials of refrigerators, augments the data set, and identifies fragmented non-magnetic materials of refrigerators using a computer vision-based deep learning method. In this study, YOLOv5s is used as the benchmark model. The CBAM module is added to the backbone to enable intelligent identification and sorting of fragmented non-magnetic materials in refrigerators. The final identification efficiency of waste refrigerators meets the requirements of industrial applications, with an accuracy rate of 98.3%, a recall rate of 96.8%, and an average accuracy of 98%. Based on the similarity of the composition of e-waste fragmented materials, this model sorting method can be applied to sorting additional e-waste fragmented materials. Furthermore, it provides the theoretical foundation for promoting e-waste resourcefulness. Implications: This paper proposes a recognition model based on YOLOv5s to solve the problems of low sorting efficiency, environmental pollution, harm to health, and resource waste of non-magnetic crushed material from refrigerators. The recognition model principally addresses the following issues: a deep learning model is developed for recognition and sorting to improve e-waste recognition and sorting efficiency. Concerning the issue of environmental benefits in an ecological environment, a vision-based automatic identification method is proposed to sort harmful waste, such as foam, to preserve the ecological environment. In response to the problem of resource waste, this project improves the purity of precious metals, resulting in a recovery rate of 99.1% for copper and 96.44% for aluminum. In other words, the cost of recovering metals has increased. The identification model of non-magnetic crushed material in refrigerators satisfies production identification and sorting requirements. In addition, the method has application and promotion value, sorting a theoretical foundation and method for identifying and classifying e-waste. [ABSTRACT FROM AUTHOR]

A finite-time thermodynamic (FTT) model of three-heat-reservoir thermal Brownian refrigerator is established in this paper. This model can be equivalent to the coupling of a thermal Brownian engine and a thermal Brownian refrigerator with heat transfer effects. Expressions for cooling load and coefficient of performance (COP) are derived by combining FTT and non-equilibrium thermodynamics (NET). The system performance is studied and compared with those of previous models. For fixed internal parameters, the thermal conductance distributions among three heat exchangers are optimized for maximal cooling load. For fixed inventory allocations, the internal parameters are also optimized for maximal cooling load. Finally, the double-maximum cooling load is obtained by optimizing internal parameters and external thermal conductance distributions simultaneously, and the optimal operating temperatures are also derived. Results show that half of total thermal conductance should be placed in condenser to reject heat to ambient under maximal cooling load regime. The heat transfer determines system performance by controlling the working temperatures and the coupling of two external loads. The system works in reversible state when COP reaches its maximum value. The new performance limits can predict that of three-heat-reservoir thermal Brownian refrigerator more accurately, and also include those of NET model. [ABSTRACT FROM AUTHOR]

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Conventional household refrigerators consist of a motor-driven compressor, evaporator, condenser, and expansion valve. To determine the optimal operation strategies of refrigerators, it is essential to investigate the overall system performance, using an appropriate simulator. This study proposed a data-driven simulator based on engineering features and machine learning algorithms for conventional household refrigerators. The most correlated variables for identifying the indoor temperature of refrigerators were identified using variable importance, and these were revealed to be the circulation fan speed, compressor operation status, and refrigerant flow direction. A data-driven simulator was constructed using Bayesian calibration, which considers the important variables, combined with a straightforward heat balance equation. The Markov Chain Monte Carlo approach was used to simultaneously calibrate three coefficients on the critical variables based on the heat balancing equation on each time step, which is consistent with the actual temperature of the container. The results revealed that the proposed approach (equation-based Bayesian calibration outperforms) standard machine learning algorithms, such as linear regression and random forest models, by 38.5%. Additionally, compared to the typical numerical analysis method, it can reduce the delivery time and effort required to develop a reliable simulator for household refrigerators. [ABSTRACT FROM AUTHOR]