Refrigerant In Temperature Range Research Articles

Mechanically strong and room-temperature magnetocaloric monolayer VSi2N4 semiconductor

In the realm of emerging two-dimensional MoSi2N4 family, the majority of research endeavors gravitate toward their versatile physical properties, while their magnetocaloric effect (MCE) for the potential refrigeration application remains uncharted. Here, we comprehensively explore the magnetic, electronic, mechanical, and magnetocaloric properties of monolayer VA2Z4 (A = Si, Ge; Z = N, P, As) family by multiscale simulations, revealing that monolayer VSi2N4 semiconductor is mechanically strong and exhibits room-temperature MCE. The nonlinear elastic response of VSi2N4 unveils strong mechanical properties, featuring a substantial in-plane Young's modulus (E2D∼ 350 N/m) and a high strength of 40.8 N/m, comparable to that of graphene. Monolayer VSi2N4 exhibits a room-temperature MCE with an extensive refrigeration temperature range up to 20 K. Furthermore, applying biaxial strain can significantly improve the maximum magnetic entropy change (−ΔSMmax) and maximum adiabatic temperature change (ΔTadmax) by 80.9% and 197.3%, respectively. Room-temperature MCE with wide working temperature and mechanical robustness make monolayer VSi2N4 an appealing candidate for magnetic refrigeration applications over large temperature range. These findings offer fresh insights for advancing the development of magnetic cooling in small-sized systems.

Analytical and experimental study on operating characteristics of a closed-cycle turbo-refrigerator for deep freezing

Compared to open-cycle turbo-refrigerators that have been extensively studied, very limited research has been done on the operating characteristics of closed-cycle turbo-refrigerators for deep freezing. Particularly, working fluid charge, as a critical operating condition, has not been considered in existing studies, and therefore a more comprehensive study on the operating characteristics of the closed-cycle turbo-refrigerator is needed. In this work, a system performance model was developed for the first time considering the working fluid charge in turbo-refrigerators, providing a great advantage in fully characterizing the system off-design operations, and a newly designed prototype for deep freezing at −120 °C was tested for model validation. Furthermore, a novel optimized operating strategy combining variable speed and working fluid charge was proposed to improve system performance. The tests demonstrated the prototype’s adaptability to a refrigeration temperature range from −125.8 °C to −62.9 °C and showed a system efficiency of 0.079 corresponding to the design point. Test data also validated the proposed model well with deviations below 15 % throughout the operating range. Further analysis shows that active speed control significantly expands the system operating range, while system efficiency penalties are imposed when dealing with reduced cooling capacities (i.e., partial-load demands) at given refrigeration temperatures by lowering the speed. Reducing the working fluid charge was found to increase system efficiency, and reason for the system efficiency improvement was revealed to be an increase in recuperator effectiveness. Combined increasing speed with reducing working fluid charge is suggested as an optimized operational strategy, especially for partial-load applications with reduced cooling capacity. By using the optimized strategy, a 30.5 % increase in system efficiency can be achieved for 15 %-reduced cooling at −120 °C.

Design of Excellent Mechanical Performances and Magnetic Refrigeration via In Situ Forming Dual-Phase Alloys.

Magnetic refrigeration technology can achieve higher energy efficiency based on the magnetocaloric effect (MCE). However, the practical application of MCE materials is hindered by their poor mechanical properties, making them challenging to process into devices. Conventional strengthening strategies usually lead to a trade-off with refrigeration capacity reduction. Here, a novel design is presented to overcome this dilemma by forming dual-phase alloys through in situ precipitation of a tough magnetic refrigeration phase within an intermetallic compound with excellent MCE. In the alloy 87.5Gd-12.5Co, incorporating the interconnected tough phase Gd contributes to enhanced strength (≈505MPa) with good ductility (≈9.2%). The strengthening phase Gd simultaneously exhibits excellent MCE, enabling the alloy to achieve a peak refrigeration capacity of 720 J kg-1. Moreover, the alloy shows low thermal expansion induced by the synergistic effect of the two phases. It is beneficial for maintaining structural stability during heat exchange in magnetic refrigeration. The coupling interaction between the two magnetic phases can broaden the refrigeration temperature range and reduce hysteresis. This study guides the development of new high-performance materials with an excellent combination of mechanical and magnetic refrigeration properties as needed for gas liquefaction and refrigerators.

Colossal barocaloric effect of plastic crystals imbedded in silicon frame near room temperature: Molecular dynamics simulation

Solid-state refrigeration technology has been attracting tremendous attention in recent decades. Plastic crystal pentaerythritol (PE) is a crucial barocaloric material in the solid-state refrigeration field due to its high entropy. However, its refrigeration temperature range and extremely low thermal conductivity are far from meeting the requirements of practical application. Here, we systematically investigate the barocaloric effect (BCE) of composite PE and silicon frame [consisting of silicon nanotube and silicene architectures (SNT-Sil)] and analyze the effects of different silicon models on the BCE performance based on molecular dynamics simulations and statistical analysis. A colossal BCE of PE/silicon frame composite is observed, and refrigeration temperature can be altered to the room temperature range by alloying neopentane (PA) into the PE matrix. It is found that the composite PE0.8PA0.2/SNT-Sil and PE0.9PA0.1/SNT-Sil demonstrate excellent comprehensive refrigeration performance near room temperature (300–320 K), with large isothermal entropy change ΔS (654–842 J kg−1 K−1), adiabatic temperature ΔT (34–47 K), and thermal conductivity κ (4.0–4.2 W m−1 K−1). The microscopic mechanism is discussed through pressure induced changes in bonding, structural, and vibrational properties. Importantly, the plastic crystal/silicon framework is easy to deform and requires smaller input work in the barocaloric refrigeration process compared to other nanomaterials such as carbon framework. This work provides important guidance on improving plastic crystals with colossal comprehensive refrigeration performance for practical applications.

Large reversible multicaloric effects over a broad refrigeration temperature range in Co and B co-doped Ni–Mn–Ti alloys

Solid-state refrigeration is considered a promising alternative to traditional vapor compression refrigeration technology. Researchers demonstrated that Ni–Mn–Ti alloys have a remarkable elastocaloric effect. However, the Ni–Mn–Ti alloy can only operate under a uniaxial stress field due to its antiferromagnetic austenite, which narrows its range of refrigeration temperatures. Here, we activated the magnetism of the alloy by replacing some Ni atoms with Co atoms. The Ni–Co–Mn–Ti–B alloy demonstrates a reversible maximum magnetic entropy change(ΔSm) of 24.9 J kg−1 K−1 and achieves an adiabatic temperature change of 7.8 K under a 7 T magnetic field. Additionally, we demonstrate that adding boron (0.2%) can improve the mechanical properties and cyclic stability in Ni–Mn–Ti alloys. The elastocaloric effect of 21.3 K with high cycle stability (1013 cycles) were successfully achieved in the directionally solidified (Ni35Co15Mn35Ti15)99.8B0.2 alloy. Furthermore, we have demonstrated that the magnetoelastic coupling effect can effectively extend the refrigeration temperature range. The alloys achieved large caloric effects in the temperature range of 240 K–340 K. This provides a new strategy for designing high-performance materials for wide-temperature-domain refrigeration.

Study on Electric Card Effect of Lead-free Piezoelectric Ceramics

The electrocaloric effect of ferroelectric materials can be used for refrigeration. This new method has the advantage of high efficiency, environmental protection and lower cost. Its variable size can satisfy the cooling requirements of different devices. However, it still exist some problems of lead-free ferroelectric ceramics refrigeration: its refrigeration temperature is less than 1 K; refrigeration temperature range is narrow; working temperature is either too high or too low. Sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) material stands out and becomes the most promising candidate to replace lead-based materials. Properties of NBT almost meet the test requirements. Near depolarization temperature, this material shows ferroelectric/antiferroelectric phase transition, which brings a larger change in electric heating temperature. In this paper, electric card effect, lead-free piezoelectric ceramic materials and the BNT-xST ceramics were introduced in detail. Among these materials, BNT-xST is considered to be a promising material due to its excellent ferroelectric property and large electromechanical coupling coefficient.

Extraordinary mechanical properties and successive caloric effects with ultrahigh cyclic stability in directionally solidified Ni36.6Co12.8Mn34.7Ti15.9 alloy

Caloric effects based on multiferroic phase transformation have attracted extensive attention for their great potential to replace the conventional vapor-compression technique. However, most multiferroic phase transforming materials are inherently brittle and their caloric effects exhibit poor cyclic stability. Here, the Ni36.6Co12.8Mn34.7Ti15.9 alloy was manufactured by the directional solidification technique. The alloy can reach maximum compressive strength and strain of 2823 MPa and 17.7% at room temperature, respectively. Under magnetic field changes of 7 T, the maximum magnetic entropy change induced by a magnetic field is 28.1 J·kg−1·K−1. A large adiabatic temperature change of 20.1 K can be obtained by applying a stress field. Besides, the adiabatic temperature change between loading and unloading cycles can be maintained at ∼11.3 K for more than 10,000 cycles. A broad refrigeration temperature range of over 80 K can be realized by combining magnetocaloric and elastocaloric effects. With the simultaneously achieved extraordinary mechanical properties and large successive caloric effects with excellent cyclic stability, the present alloy has a great prospect for solid-state refrigeration applications.

Giant barocaloric effects with a wide refrigeration temperature range in ethylene vinyl acetate copolymers.

Solid-state cooling technology based on the caloric effects of phase-transition materials has been a research hotspot due to its environmental friendliness and high efficiency, but limited for practical applications due to its narrow working temperature region. Here, we report giant barocaloric effects based on pressure-driven liquid-solid phase transitions in elastic copolymers of ethylene and vinyl acetate. Giant adiabatic temperature changes of up to 29.6/-26.9 K are directly observed under rapid compressions/decompressions of 400 MPa near the liquid-solid phase transition points. Strikingly, since both the solid and the liquid sides can show giant barocaloric effects, a very broad refrigeration temperature region of more than 110 K is achieved in these copolymers. Furthermore, a cooling prototype is designed to demonstrate the potential applications of these liquid/elastic barocaloric materials. Our study sheds light on exploring liquid-solid phase transition materials for the next-generation refrigerators.

Effect of LiNbO3 on the electrocaloric performance of 0.94BNT-0.06BT ceramic materials

Considering that the electric refrigeration temperature range of 0.94BNT-0.06BT ceramic materials is 100 ∼ 140 °C, the electric refrigeration performance of the 0.94BNT-0.06BT ceramic material system was modified by LiNbO3 doping to reduce the cooling temperature. As a result, the refrigeration temperature range of the 0.94BNT-0.06BT ceramic material system was lowered to 25 ∼ 80 °C, achieving its cooling effect near room temperature, and in this temperature range, the adiabatic temperature changes ΔT > 0.6K.

Experimental and numerical study on performance of hybrid refrigeration system that combines vapor compression and thermoelectric systems

As high-quality food preservation has become an important aspect of daily life, a need has developed for domestic household refrigerators with a wide refrigeration temperature range. The temperature range of domestic household refrigerators is generally above −20 °C. In this study, a hybrid refrigeration system that combined vapor compression refrigeration (VCR) and a thermoelectric refrigerator (TER) is investigated for the freezer compartment of a domestic refrigerator with a volume of 0.018 m3. Although an additional 99.5 W of electrical power is consumed, a lower temperature of −38.1 °C is experimentally achieved in the deep freezer compartment of a compact VCR–TER system, with no noise or mechanical parts. In contrast, a temperature of only −8.8 °C is obtained in a typical VCR system. A three-dimensional numerical model is applied to study the performance of the finned heat sink of the TER using FLUENT. The effects of the fin height and fin pitch on the thermal resistance and pressure drop are investigated. The results show that the thermal resistance decreases with an increase in the fin height and increases with an increase in the fin pitch. An optimized finned heat sink with a fin height of 50 mm is obtained, which has a thermal resistance of 0.05 °C/W. It has a higher cooling capacity of 53.6 W than the heat sink with the original fin height of 30 mm. The VCR–TER system has potential application to low-temperature domestic refrigeration systems with a small size and small cooling capacity.

A Review of the Cascade Refrigeration System

This paper provides a literature review of the cascade refrigeration system (CRS). It is an important system that can achieve an evaporating temperature as low as −170 °C and broadens the refrigeration temperature range of conventional systems. In this paper, several research options such as various designs of CRS, studies on refrigerants, and optimization works on the systems are discussed. Moreover, the influence of parameters on system performance, the economic analysis, and applications are defined, followed by conclusions and suggestions for future studies.

Multiple transitions and wide refrigeration temperature range in R3NiSi2 (R = Tb, Dy) compounds

In this work, orthorhombic polycrystalline Tb3NiSi2 and Dy3NiSi2 compounds were prepared and magnetocaloric effect during multiple magnetic transitions was investigated in detail. Tb3NiSi2 compound displays four different magnetic transitions at 94 K, 115 K, 134.2 K, and 140.6 K, respectively. The maximal value of magnetic entropy change are about 4.5 J/kg K and 11.1 J/kg K at 141 K for Tb3NiSi2compound under a field change of 0–2 T and 0–7 T, respectively. For the Dy3NiSi2 compound, three obvious magnetic transitions are found at 29.3 K, 65.4 K, and 76.6 K and the maximal value of magnetocaloric effect are about 3.6 J/kg K and 10.8 J/kg K at 77 K for a field change of 0–2 T and 0–7 T, respectively. Due to the multiple magnetic transitions, both compounds exhibit the wide refrigeration temperature range and considerable refrigerant capacity. The results reveal that the value of refrigeration temperature range and refrigerant capacity are 66.9 K and 549.1 J/kg for Tb3NiSi2 compound, and 64.0 K and 489.6 J/kg for Dy3NiSi2 compound, respectively. Therefore, R3NiSi2-family compounds have a potential application in middle temperature magnetic refrigeration.

Experimental investigation of displacer rod diameter effect on pulse tube cryocooler

Abstract Displacer type pulse tube refrigerator has been the emphasis of research in refrigeration due to its high theoretical efficiency and wide refrigeration temperature range from 77 K to near room temperature. A pulse tube refrigerator with displacer as phase shifter was built and tested. According to the results, there is an optimum displacer rod diameter for getting high efficiency when the parameters of the mass-spring-damper system in displacers almost keep constant. The results also indicated that the cooling power 120 W was obtained at 178.8 K with the input power 684.6 W, which leaded to an efficiency of 11.2% of Carnot, about 25% higher when the inertance tube phase shifter was replaced by displacer.

The use of barocaloric effect for energy saving in a domestic refrigerator with ethylene-glycol based nanofluids: A numerical analysis and a comparison with a vapor compression cooler

This paper focuses on barocaloric refrigeration that could represent a practicable environmentally friendly alternative to vapor compression. The energy performances of an active barocaloric refrigerator working as a domestic cooler are evaluated by means of a 2-Dimensional model, already validated in previous investigations. The energy performances are also compared with experimental data referred to a household vapor compression refrigerator working with HFC134a. The active barocaloric regenerative refrigeration cycle is supposed to work as a domestic refrigerator in temperature range of 255 ÷ 290 K. The heat-transfer fluid is a mixture of 50%ethylene-glycol-50%water, whereas acetoxy silicone rubber is the solid-state refrigerant. In order to enhance the energy performances of the solid-state refrigerator the use of Cu-based nanofluids in the anti-freezing mixture was tested. The addition of Cu-nanoparticles to the 50%ethylene-glycol- 50%water mixture ensures a moderate enhancement of the energy performances (the maximum temperature span, cooling power and coefficient of performance enhancements are +4.0%, +7.3% and +6.7%, respectively). The analysis shows that barocaloric refrigeration can be a promising new technology in the field of domestic refrigeration for energy saving because it always overperforms vapor compression.

Breakdown mechanism of CF4 and N2 binary gas in refrigeration temperature range

The mechanism of gas discharge in refrigeration temperature range is still not clear. N2, CF4, 20% CF4+N2 and 50%CF4+50%N2 binary gas mixtures were tested under the conditions of–153–25 °C and 50–2000 Pa. The experimental results show that the minimum of Paschen curves of all test samples shifts to low pressure, from 500 Pa to 200 Pa. The value of Paschen curve minimum of N2 shows remarkable fluctuation. This fluctuation is explained by molecule agglomeration and electronic mean energy. The fluctuation decreases with the increasing mixing ratio of CF4. What’s more, the value of Paschen curve minimum of CF4 decreases with temperature. This phenomenon is ascribed to attach-radiation and secondary process.

Breakdown characteristics of CF4 and CF4/N2 hybrid gas in refrigeration temperature range

Common insulation gas cannot normally work in refrigeration temperature range (153−243 K), especially in extremely cold regions. To solve this problem, this essay uses cubic equation combined with two-parameter model in theorem of corresponding states to estimate dew-point of hybrid gas. The influence of temperature on mixing ratio is studied by using van der Waals equation. The result shows that the mixing ratio is stable during temperature-fall period. Insulation property of CF4 and CF4/N2 in refrigeration temperature range is studied through self-designed low-temperature test system. The result shows when the density of hybrid gas is invariable, temperature changing has less influence on breakdown voltage, and when the mixing ratio is 20%, CF4/N2 is the greatest potential hybrid gas.

The Use and Performance of Household Refrigerators: A Review.

The domestic refrigerator is now a common household device with very few households in the developed world not possessing 1, or more, for the storage of chilled foods. Domestic storage is the last, and in many respects the most important, link in the food chill chain. Inadequate domestic refrigeration or cooling is frequently cited as a factor in incidents of food poisoning. The authors reviewed the temperature performance of refrigerators in 2008. This new review builds on that review, covering studies that have been published since (and those that were unfortunately missed in the first review), and also seeks to put this important stage of the food cold chain in its context. It is clear from the published data that many refrigerators throughout the world are running at higher than recommended temperatures. It is also clear that, despite improvements in energy use, the temperature performance and use of refrigerators have not changed significantly in the last 40 or so years. Many householders still remain unaware of the recommended refrigeration temperature range, how to ensure that the correct refrigeration temperature range is achieved, the importance of monitoring that it is being maintained, and the potential hazards of temperature abuse.

The system study of 1:13 phase formation, the magnetic transition adjustment, and magnetocaloric property in La(Fe,Co)13−xSix alloys

The effects of Co on the formation of NaZn13-type phase in as-cast and annealed LaFe16−xCoxSi1.4 and LaFe11.6Si1.4−xCox alloys have been investigated systematically by XRD, SEM, and EDS, respectively. In LaFe11.6Si1.4−xCox alloys, the introduction of Co will hamper the formation of 1:13 and LaFeSi phases, and help the formation of αof (Co, Si) solid solution, so there is almost only α-Fe(Co, Si) solid solution when x reaches 0.7 in as-cast and annealed LaFe11.6Si1.4−xCox alloys. Although the amounts of 1:13 phase increases when x reaches 0.7 in as-cast LaFe16−xCoxSi1.4 alloys, there is a small amount of α-Fe in LaFe11.6−xCoxSi1.4 alloys annealed at 1523K (5h), which indicates that the annealing time for obtaining a 1:13 single-phase cannot be shortened in our high-temperature and short-time annealing. The studies on the magnetic properties show that the Curie temperature TC goes up from 207K to 285K with increase of Co content from x=0.1 to 0.8. The introduction of Co element weakens the first order magnetic phase transition, which results in the change of magnetic transition type from first to second order at about x=0.3–0.5. At the same time, it has effects on the phase transition temperature interval and magnetic filed interval, and the changing rate of magnetic entropy change dependence on the Co content in LaFe16−xCoxSi1.4 alloys. The maximum entropy values of LaFe11.6−xCoxSi1.4 alloys decrease with the increase of Co content, but the relative cooling power does not decrease, the reason of which is that the phase transition temperature interval increases and the first order phase transition character decreases, and the effective refrigeration temperature range becomes big, which is useful to the application of magnetic refrigeration material.

Thermodynamic analysis of absorption refrigeration cycles using ionic liquid + supercritical CO 2 pairs

Absorption refrigerators are alternative systems to conventional compression cycles in which the energy necessary for the refrigeration is provided by heating instead of mechanical power. Commercial absorption refrigerators use two absorbent/refrigerant pairs: NH 3–H 2O and H 2O–LiBr. These systems have some limitations due to the difficulty of separating absorbent and refrigerant, the narrow refrigeration temperature range, or the possibility of corrosion and salt deposition. The application of ionic liquids as absorbents with supercritical carbon dioxide as refrigerant can solve some of these problems because separation of ionic liquid from CO 2 is easy due to the negligible vapor pressure of ionic liquids. In this work, suitable ionic liquids–CO 2 pairs have been selected considering their phase equilibrium properties, calculated with the Group-Contribution equation of state developed by Skjold-Jørgensen. The energetic efficiency of the process with ionic liquids has been estimated by calculation of the Coefficient of Performance (COP) of the process. It has been found that the process with ionic liquids has a lower COP than conventional NH 3–H 2O systems due to the necessity of operating with a higher solution flowrate. Nevertheless, near-optimum performance is obtained in a wide range of process conditions.

Gd–Dy–Al–Co bulk metallic glasses with large magnetic entropy change and refrigeration capacity

Novel Gd 56− x Dy x Al 24Co 20 ( x = 0, 14, 17) bulk metallic glasses (BMGs) were prepared by copper mold casting. They exhibit magnetic entropy changes (Δ S M ) comparable to that of Gd 53Al 24Co 20Zr 3 BMG and crystalline Gd. Moreover, these glassy alloys have broad entropy change peaks, resulting in the refrigeration capacities of 751.4 J kg −1, 702.8 J kg −1, and 682.3 J kg −1 for Gd 56Al 24Co 20, Gd 42Dy 14Al 24Co 20, and Gd 39Dy 17Al 24Co 20 at 5 Tesla. The large magnetocaloric effect makes these BMGs attractive candidates as magnetic refrigerant in temperature range of 50–140 K. It is also found that the Curie temperature of this kind of metallic glass linearly declines with the increase of Dy. The Δ S M of metallic glasses reaches maximum at certain content of Dy. These findings are expected to provide a meaningful guidance for the composition design of rare earth based glassy alloys for refrigeration application.