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Abstract The application of external stimuli such as the magnetic and electric field in magnetocaloric and electrocaloric materials, and stress and pressure in elastocaloric and barocaloric materials give rise to a new generation of a refrigeration technology based on caloric materials which are considered an emerging alternative to classical refrigeration. Active caloric regenerator (ACR) made in parallel plates is studied under a large number of materials with Comsol multiphysics for a 2D numerical model. In this work, we compare various types of caloric materials, in terms of their thermodynamic properties, working mechanisms, and potential applications as solid refrigerant on caloric refrigeration devices. For this purpose, the energy equation, Navier-Stocks equation, and continuity equation are considered to study the heat transfer phenomena in refrigerator. The water was used as a carrier fluid to transport the thermal energy from the solid refrigerants to heat exchanger. This study is performed at velocity 0.06 m/s and the frequency 2 Hz at room temperature. Among them, Gadolinium show the best results in term temperature span, coefficient of performance, and the cooling power, higher than every other caloric materials, conferring to magnetocaloric cooling globally the most promising system. Our analysis provides insights into the selection and optimization of caloric materials for caloric refrigeration, which can contribute to the development of sustainable energy systems.

The application of external stimuli such as the magnetic and electric field in magnetocaloric and electrocaloric materials, and stress and pressure in elastocaloric and barocaloric materials give rise to a new generation of a refrigeration technology based on caloric materials which are considered an emerging alternative to classical refrigeration. Active caloric regenerator (ACR) made in parallel plates is studied under a large number of materials with Comsol multiphysics for a 2D numerical model. In this work, we compare various types of caloric materials, in terms of their thermodynamic properties, working mechanisms, and potential applications as solid refrigerant on caloric refrigeration devices. For this purpose, the energy equation, Navier-Stocks equation, and continuity equation are considered to study the heat transfer phenomena in refrigerator. The water was used as a carrier fluid to transport the thermal energy from the solid refrigerants to heat exchanger. This study is performed at velocity 0.06 m/s and the frequency 2 Hz at room temperature. Among them, Gadolinium show the best results in term temperature span, coefficient of performance, and the cooling power, higher than every other caloric materials, conferring to magnetocaloric cooling globally the most promising system. Our analysis provides insights into the selection and optimization of caloric materials for caloric refrigeration, which can contribute to the development of sustainable energy systems. [ABSTRACT FROM AUTHOR]

• A 23-tube, single-stage staggered active elastocaloric regenerator was developed. • Fluid-solid ratio, (un)loading time, and strain significantly impact performance. • A maximum temperature span of 16.6 K was achieved at zero load conditions. • Nitinol tubes withstood over 30,000 cycles without failure. Elastocaloric solid-state refrigerants have a lower environmental impact compared to conventional vapor compression refrigerants, but they require significant advancements to gain widespread implementation. Two barriers that prevent adoption are the low-temperature lift and poor fatigue life. This paper presents a compression-loaded, staggered-tube active elastocaloric regenerator designed to address these challenges, along with the optimal operating parameters for the system. We conducted a sensitivity analysis on a single-stage device and identified fluid-solid ratio, cycle time, and applied strain as key factors affecting thermal response. Test results for the regenerator yielded a maximum steady-state temperature span of 16.6 K (9.7 K in heating and 6.8 K in cooling) at 4% strain and under zero load conditions, over two times larger than the baseline value. The tubes also withstood over 30,000 cycles without failure. The outcomes shown in this paper contribute to the foundation—in both design and operating conditions—of growing works aimed at demonstrating high-performing caloric devices. [ABSTRACT FROM AUTHOR]

The elastocaloric effect denotes the ability of a material to release or absorb heat when the material is stretched and released respectively. This effect may be used to design an alternative cooling device. This work focuses on the development of a cooling device using natural rubber (NR) as the elastocaloric material. It consists of a solid–solid heat exchange between a cyclically stretched elastocaloric material and two exchangers, respectively put in contact with the elastocaloric material when it is stretched or released. An experimental device was designed and tested in order to assess the temperature span and cooling power ( PC ) achievable by NR based single stage device. The effect of the thickness of the NR is also discussed. It is shown that it was possible to transfer nearly 60% of the heat absorption potential of the NR from the cold heat exchanger. From the measurements, the highest PC was found to be 390 mW (430 W kg ^−1 ) for a 600 µ m thick sample, and 305 mW (540 W kg ^−1 ) for a 400 µ m thick sample. The temperature span was found to be similar for both materials, ranging 1.5 °C–1.9 °C.

The widespread need to pump heat necessitates improvements that will increase energy efficiency and, more generally, reduce environmental impact. As discussed at the recent Calorics 2022 Conference, heat-pump devices based on caloric materials offer an intriguing alternative to gas combustion and vapor compression. [ABSTRACT FROM AUTHOR]

Solid‐state refrigeration has received widespread attention recently because of its high refrigeration efficiency and environmental protection. Compared with other solid‐state refrigeration technologies, elastocaloric effects have great application potential. However, the current temperature change of elastocaloric effects is still low. This work explores the change law of phase transition temperature of ferroelectric materials by applying the external stress based on the thermodynamic calculation. It can be found that ferroelectric materials' positive and negative elastocaloric effects can peak at the same temperature, so here a device to combine the positive and negative elastocaloric effects of Ba0.7Sr0.3TiO3 and BaZr0.015Ti0.085O3 is designed. This device can achieve a ΔT of 3.18 K near room temperature under applied stress of 200 MPa, which is twice as large as that of 1.4 K in BCZTO‐Fe under the same stress condition. And it can be raised to 4.1 K after applying an electric field of 10 MV m−1. It is the first time to combine positive and negative elastocaloric effects to achieve high cooling near room temperature, which provides a new solution for efficient cooling near room temperature. [ABSTRACT FROM AUTHOR]

Liquid crystalline elastomers (LCEs) are soft materials that associate order and deformation. Upon deformation, mechanically induced changes order affect entropy and can produce a caloric output (elastocaloric). Elastocaloric effects in materials continue to be considered for functional use as solid state refrigerants. Prior elastocaloric investigations of LCEs and related materials have measured ≈2 °C temperature changes upon deformation (100% strain). Here, the elastocaloric response of LCEs is explored that are prepared with a subambient nematic to isotropic transition temperature. These materials are referred as "isotropic" liquid crystalline elastomers. The LCEs are prepared by a two-step thiol-Michael/thiol-ene reaction. This polymer network chemistry enhances elastic recovery and reduces hysteresis compared to acrylate-based chemistries. The LCEs exhibit appreciable elastocaloric temperature changes upon deformation and recovery (> ± 3 °C, total ΔT of 6 °C) to deformation driven by minimal force (<< 1 MPa). Notably, the strong association of deformation and order and the resulting temperature change attained at low force achieves a responsivity of 14 °C MPa -1 which is seven times greater than natural rubber., (© 2024 Wiley‐VCH GmbH.)

With the increased environmental awareness, the search for environmentally friendlier heat-management techniques has been the topic of many scientific studies. The caloric materials with large caloric effects, such as the electrocaloric (EC) and elastocaloric (eC) effects, have increased interest due to their potential to realize new solid-state refrigeration devices. Recently, caloric properties of soft materials, such as liquid crystals (LCs) and LC elastomers (LCEs), are getting more in the focus of caloric materials investigations, stimulated by large caloric effects observed in these materials. Here, an overview of recent direct measurements of large caloric effects in smectic LC 14CB and main-chain LCEs is given. Specifically, high-resolution thermometric measurements revealed a large EC response in 14CB LC exceeding 8 K. Such a large effect was obtained at a relatively moderate electric field of 30 kV cm ^−1 compared to solid EC materials. We demonstrate that such a small field can induce the isotropic to smectic A phase transition in 14CB, releasing or absorbing relatively large latent heat that enhances the EC response. Furthermore, it is demonstrated that in main-chain LCEs, the character of the nematic to isotropic transition can be tuned from the supercritical towards the first-order regime by decreasing the crosslinkers’ density. Such tuning results in a sharper phase transition and latent heat that enhance the eC response, exceeding 2 K and with the eC responsivity of 24 K MPa ^−1 , about three orders of magnitude larger than the average eC responsivity found in the best shape memory alloys. Significant caloric effects in soft LC-based materials, observed at much smaller fields than in solid caloric materials, demonstrate their ability to play an important role as new cooling elements, thermal diodes, and caloric-active regeneration material in new heat-management devices.

Cu-Al-Mn alloys display martensitic transformation over a wide range of temperatures. In addition to low cost, this alloy is known for its low transformation stress with reasonable latent heat favoring elastocaloric applications. However, the ductility of Cu-Al-Mn can be limited owing to ordering and intergranular fracture. Through rapid solidification by melt spinning, we show that Cu-Al-Mn ribbon can be made highly ductile (greater than 8% tensile strain in the as-spun state and 10% tensile strain after heat treatment). The ductility of the melt-spun ribbon is related to the suppression of L2 _1 ordering that is characterized through magnetic property measurement. Heat treatment of the ribbon promotes bamboo grain formation, and the latent heat is increased to 6.4 J g ^−1 . Under tensile conditions, we show that the ribbon exhibited about 4 °C temperature change (4.4 °C on heating and 4.2 °C on cooling from 6.3% strain).

Multiferroic materials with strong coupling between different degrees of freedom are prone to exhibit giant multicaloric effects resulting from the application or removal of diverse external fields. These materials exhibit a synergic response to the combined action of two fields when the monocaloric effects are both conventional (or both inverse), while a non-synergic response occurs when one of the monocaloric effects is conventional and the other is inverse. In all cases, the multicaloric properties (isothermal entropy and adiabatic temperature changes) do not result from the simple addition of the corresponding monocaloric quantities because there is a contribution from the interplay between degrees of freedom (cross-coupling term). In this paper, we analyse in detail the contribution of the cross-coupling term to the multicaloric entropy values obtained for both synergic and non-synergic multicaloric materials. We first introduce basic thermodynamic concepts accounting for the multicaloric effects, and next the contribution from the cross-coupling term is illustrated via several model examples. We finally analyse the realistic situation for two prototype materials with synergic and non-synergic multicaloric effects.

We report on a versatile experimental setup for the study of the electro-magneto-elasto-thermal coupling for bulk materials having coupling properties. The setup enables measurement of stress and electrical resistivity in a 80–450 K temperature range under controlled uniaxial pressure in a magnetic field up to 8 T. The strong influence of uniaxial pressure and magnetic field on strain and transport properties is shown for Ni-Co-Mn-In Heusler single crystal material. Phase transformation, magnetostress and magnetic field-induced phase transformation, and elastocaloric effect can be estimated using this versatile setup. This device is very complementary to the studies focused on the modeling of thermo-electro-magneto-mechanical behavior for functional materials. [ABSTRACT FROM AUTHOR]

Italy has not yet presented to the scientific community any elastocaloric prototype suitable for refrigeration/air conditioning. The SUSSTAINEBLE project was born from the idea to build a demonstrative elastocaloric prototype for environmental conditioning. The prototype is planned to be rotary and composed by a few bunches of elastocaloric wires crossed by air as heat transfer fluid. Many are the parameters to be investigated before the realization of the device. A numerical practical tool would help to easily optimize the prototype. In this paper a two-dimensional tool of a single bunch of elastocaloric wires based on finite-element method is introduced; it can reproduce step by step the velocity and the pressure field of fluid to predict more accurately the solid-to-fluid heat exchange. The results of a test campaign mostly focused on the optimization of the frequency of the cycle, fluid velocity and the distance between the elastocaloric wires are presented. The results reveal that: (i) 0.12 Hz as frequency; (ii) 7 m s-1 as velocity; (iii) 1.0 mm as optimal wire distance, would better satisfy the trade-off existing in the maximization of temperature span and cooling power per mass unit: 23.7 K and 311.97W kg-1 are the values achieved, respectively. [ABSTRACT FROM AUTHOR]

Materials exhibiting a large caloric effect could lead to the development of a new generation of heat-management technologies that will have better energy efficiency and be potentially more environmentally friendly. The focus of caloric materials investigations has shifted recently from solid-state materials towards soft materials, such as liquid crystals and liquid crystalline elastomers. It has been shown recently that a large electrocaloric effect exceeding 6 K can be observed in smectic liquid crystals. Here, we report on a significant elastocaloric response observed by direct elastocaloric measurements in main-chain liquid crystal elastomers. It is demonstrated that the character of the nematic to paranematic / isotropic transition can be tuned from the supercritical regime towards the first-order regime, by decreasing the density of crosslinkers. In the latter case, the latent heat additionally enhances the elastocaloric response. Our results indicate that a significant elastocaloric response is present in main-chain liquid crystalline elastomers, driven by stress fields much smaller than in solid elastocaloric materials. Therefore, elastocaloric soft materials can potentially play a significant role as active cooling/heating elements in the development of new heat-management devices. [ABSTRACT FROM AUTHOR]

Ni–Mn-based shape memory alloy is a promising candidate as the solid-state elastocaloric refrigerant in the micro- or nano-refrigeration fields owing to the required small driving force. In this letter, we report a multielement alloying strategy, i.e., the co-substitution of non-magnetic element and boron for Mn, to improve the elastocaloric refrigeration efficiency and mechanical properties simultaneously. Under Cu and B co-substitution, a large adiabatic temperature change of –12.8 K and a giant specific adiabatic temperature change of 41.0 K/GPa were obtained in the directionally solidified Ni 50 (Mn 31.7 Cu 2.5 B 0.3)In 15.5 alloy. The proposed alloying manner is also favorable to enhance fracture resistance and cyclability. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Italy has not yet presented to the scientific community any elastocaloric prototype suitable for refrigeration/air conditioning. The SUSSTAINEBLE project was born from the idea to build a demonstrative elastocaloric prototype for environmental conditioning. The prototype is planned to be rotary and composed by a few bunches of elastocaloric wires crossed by air as heat transfer fluid. Many are the parameters to be investigated before the realization of the device. A numerical practical tool would help to easily optimize the prototype. In this paper a two-dimensional tool of a single bunch of elastocaloric wires based on finite-element method is introduced; it can reproduce step by step the velocity and the pressure field of fluid to predict more accurately the solid-to-fluid heat exchange. The results of a test campaign mostly focused on the optimization of the frequency of the cycle, fluid velocity and the distance between the elastocaloric wires are presented. The results reveal that: (i) 0.12 Hz as frequency; (ii) 7 m s−1 as velocity; (iii) 1.0 mm as optimal wire distance, would better satisfy the trade-off existing in the maximization of temperature span and cooling power per mass unit: 23.7 K and 311.97 W kg−1 are the values achieved, respectively.

• A state of the art of all the developed solid-state caloric prototypes was presented. • The devices were classified as magnetocaloric, electrocaloric, elastocaloric or barocaloric. • The main design features and the energy performances shown were reported for each device. • A point of view of the future perspectives is proposed in the conclusions. The solid-state processes for cooling and heat pump technologies are based on the well-known caloric effects (magneto-, electro-, elasto- and baro-caloric). With an interest arisen in 1976, year of the development of the first room-temperature magnetic refrigerator, up to a few years ago, magnetocaloric was among the most investigated caloric cooling techniques and it was considered among the main solid-state alternatives to vapor-compression cooling and heat-pumping. During such period, a remarkable number of prototypes of magnetic refrigerators or heat pumps was built. Recently, the attention toward all the four caloric effects has recently grown; therefore, an increase in projects on solid-state prototype developing (not only on magnetocaloric) was observed. The intention of this paper is to offer a state-of-the-art of all the solid-state prototypes for cooling and heat pumps processes, devoted to room temperature operations, developed before the year 2019. [ABSTRACT FROM AUTHOR]

Caloric refrigeration is an emerging class of cooling technologies based on caloric effects detected in ferro-caloric solid-state materials. Depending of the nature of the driving field, it is possible distinguishing four main caloric refrigerations: magnetocaloric, electrocaloric, elastocaloric and barocaloric. Therefore, caloric refrigeration is based on solid-state materials, unlike vapor compression, nowadays still the most diffused cooling technique, whom employs fluids as refrigerants. Solid-state materials do not provide a direct contribution in global warming, since they do not disperse in the atmosphere, but only an indirect impact is registered when they are employed as refrigerants in cooling systems. On the other side, a vapor compression plant is characterized by both direct and indirect contributions to global warming. The main parameter to evaluate global warming impact and carbon-dioxide emissions coming out from a cooler is the Total Environmental Warming Impact (TEWI) index, which accounts both the direct and indirect contributions produced. In this paper a numerical ?TEWI analysis is presented, comparing the environmental impact of a caloric refrigerator, operating with different caloric materials, with the one of a vapor compression cooler working with HFC134a. [ABSTRACT FROM AUTHOR]

Caloric refrigeration can be a viable alternative to the traditional vapour compression technology since a caloric solid refrigerant has zero vapour pressure and therefore is ecological with no direct Ozone Depletion Potential and zero direct Global Warming Potential. Caloric refrigeration embraces four main cooling techniques, each one based on a different caloric effect. This paper is focused upon materials that display mechanocaloric properties, with a transition induced through the application of variable pressure (barocaloric cooling) or uniaxial stress (elastocaloric cooling). Materials that display solidstate caloric effects driven by applied pressure/stress could lead to more accessible and economic technological solutions. By means of a two-dimensional mathematical model an energy analysis is performed with the most performing elastocaloric and barocaloric materials to explore the potential of mechanocaloric cooling. Temperature span, cooling power and coefficient of performance have bene evaluated. Results demonstrate best mechanocaloric materials, like Cu68.13Zn15.74Al16.14 and (NH4)2MoO2F4, provide energy performances better than those of traditional vapour compression plants. [ABSTRACT FROM AUTHOR]

Elastocaloric cooling (ECC) is considered as one of the candidates to replace vapor compression cycles, which use refrigerants with global warming potential (GWP) as working fluids. In order to properly understand the ECC system performance, it is critical to conduct analysis at the integrated system level. Also, due to the cyclic operation of an ECC system, dynamic modeling becomes necessary to capture the associated transients. In this study, for air conditioning applications, a unique air-to-air ECC dynamic system model has been developed to simultaneously simulate the elastocaloric effect of NiTi, heat transfer, and water transport in the system. Key parameters have been identified from sensitivity analysis of various options as well as the dynamic coupling among components. A systematic methodology has been further developed to identify practical solutions of the integrated ECC system, which provides a basis for comparison against other existing cooling technologies. Performance of an integrated ECC system with 1.2 kW net cooling capacity has been optimized using the NSGA-II method for maximum coefficient of performance (COP) within operational constraints. It has been demonstrated that effective system design and energy-efficient operation can only be achieved from optimization of the entire integrated system instead of a component or subsystem. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMAs) with small stress-hysteresis and wide superelasticity temperature window are highly desired for elastocaloric applications. In this study, a nanocrystalline T i 50 N i 42 C u 6 Fe 2 SMA is fabricated by casting, forging, wire-drawing and annealing. The alloy exhibits superelasticity with a narrow average stress-hysteresis of ∼180 MPa over a temperature window from 213 K to 323 K. The temperature change of the elastocaloric effect is calculated to be ∼28 K. In situ synchrotron X-ray diffraction measurements suggest that the small hysteresis is probably attributed to the enhanced lattice compatibility as quantified by the cofactor condition parameters (λ 2 , X I and X II). • Nanograined Ti 50 Ni 42 Cu 6 Fe 2 SMA was fabricated by wire-drawing. • Alloy shows superelasticity from 213 K to 323 K, with 180 MPa stress-hysteresis. • Superior lattice compatibility was found by in situ synchrotron XRD. [ABSTRACT FROM AUTHOR]

Shape memory alloys (SMA) are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition, gives rise to giant mechanocaloric effects. In non-magnetic SMA, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of alloys is strongly affected by uniaxial stress, whereas it is basically insensitive to hydrostatic pressure. As a result, non-magnetic alloys exhibit giant elastocaloric effects but negligible barocaloric effects. By contrast, in a number of magnetic SMA, the lattice distortion at the martensitic transition involves a volume change in addition to the shear strain. Those alloys are affected by both uniaxial stress and hydrostatic pressure and they exhibit giant elastocaloric and barocaloric effects. The paper aims at providing a critical survey of available experimental data on elastocaloric and barocaloric effects in magnetic and non-magnetic SMA. [ABSTRACT FROM AUTHOR]

In the framework of elastocaloric (eC) refrigeration, the fatigue effect on the eC effect of natural rubber (NR) is investigated. Repetitive deformation cycles at engineering strain regime from 1 to 6 results in a rapid rupture (approx. 800 cycles). Degradation of properties and fatigue life are then investigated at three different strain regimes with the same strain amplitude: before onset strain of strain-induced crystallization (SIC) (strain regime of 0-3), onset strain of melting (strain regime of 2-5) and high strain of SIC (strain regime of 4-7). Strain of 0-3 leads to a low eC effect and cracking after 2000 cycles. Strain of 2-5 and 4-7 results in an excellent crack growth resistance and much higher eC effect with adiabatic temperature changes of 3.5K and 4.2 K, respectively, thanks to the effect of SIC. The eC stress coefficient index γ (ratio between eC temperature change and applied stress) for strains of 2-5 and 4-7 are γ2-5 =4.4KMPa-1 and γ4-7 =1.6KMPa-1, respectively, demonstrating the advantage of the strain regime 2-5. Finally, a highcycle test up to 1.7 x 105 cycles is successfully applied to the NR sample with very little degradation of eC properties, constituting an important step towards cooling applications. [ABSTRACT FROM AUTHOR]

Materials with large caloric effect have the promise of realizing solid-state refrigeration which has potential to be more efficient and environmentally friendly compared with current cooling technologies. Recently, the focus of caloric effects investigations has shifted towards soft materials. An overview of recent direct measurements of the large electrocaloric effect (ECE) in a composite mixture of a liquid crystal and nanoparticles (NPs) and large elastocaloric (eC) effect in main-chain liquid crystal elastomers is given. In mixtures of 12CB liquid crystal with functionalized CdSSe NPs, an ECE exceeding 5K was found in the vicinity of the isotropic to smectic A phase transition. It is shown that the NPs smear the isotropic to smectic coexistence range in which a large ECE is observed due to latent heat enhancement. NPs acting as traps for ions reduce the moving-ion density and consequently the Joule heating. Direct eC measurements indicate that the significant eC response can be found in main-chain liquid crystalline elastomers, but at a fraction of the stress field in contrast to other eC materials. Both soft materials could play a significant role as active cooling elements or parts of thermal diodes in development of new cooling devices. [ABSTRACT FROM AUTHOR]

With advances in solid-state cooling materials in the past decade, non-vapor compression technologies, or not-in-kind (NIK) cooling technologies have garnered great attention. Therefore, a universal performance index is urgently needed to compare these NIK technologies with each other and vapor compression cooling as well. In this study, a systematic method is developed to visualize the contributions to the coefficient of performance (COP) from materials (working fluids) level to the system level as a function of temperature lifts. Since the materials level COP depends solely on the materials properties under the specified cycle, it can be used for comparing refrigerants for all NIK technologies. We chose the water-cooled water chiller operating under identical conditions as the basis for the system performance comparison of all NIK cooling technologies. Upon normalizing the system COP to the Carnot COP, its variation with the system temperature lift reveals the intrinsic potential applications for each NIK cooling technology. [ABSTRACT FROM AUTHOR]

First paper reported the experimental measurement of various caloric effects in Pb(Mn 1/3 Nb 2/3 )O 3 -32PbTiO 3 (PMN-PT) single crystals (Chauhan et al., 2015). This study expands upon the former one by discussing various modes for quantifying caloric effects in ferroelectric single crystals, based on different forms of Maxwell’s relations. Based on suitable combination between the dependent and driving factors, four types of caloric responses can be classified. This allows one to study previously unexplored components of the actual or net caloric behavior in a ferroelectric material. It is observed that quantification of entropy and temperature change in a ferroelectric material is highly dependent on the mode of measurement used and the nature of variables employed. A peak Δ T EC of −0.267 K is observed for applied electric field of 0–1.5 MV m −1 at 313 K, while a maximum Δ T eC of 0.27 K is predicted for applied stress of 0–14 MPa (313 K). Correspondingly a largest Δ T PC of −0.11 K is observed at 333 K (0–14 MPa) under electric field biasing of 1.5 MV m −1 while maximum cooling obtained through Δ T iPC is observed to be −1.01 K (323 K) for 0–1.5 MV m −1 electric field strength. Additionally it was observed that complimentary caloric effects are competing in nature and could act to oppose one another. This raises the concern towards selection of dependent and driving variables for suitable prediction of actual caloric response in a ferroelectric. Experimental verification is sought for corroboration of proposed theories. The results also hint at the large unexplored potential of bulk ferroelectric materials for solid-state refrigeration. [ABSTRACT FROM AUTHOR]

In recent years, several emerging technologies in the domain of solid-state physics have been investigated as serious alternatives for future refrigeration, heat pumping, air conditioning, or even power generation applications. These technologies relate to what is called caloric energy conversion, i.e., barocalorics, electrocalorics, magnetocalorics, and elastocalorics. Of these technologies, the greatest progress has been observed in the domain of magnetic refrigeration. However, in the recent few years, significant research efforts have also been made in the field of electrocaloric and elastocaloric refrigeration. Many of these technologies suggest the possibility for improvements in energy efficiency, compactness, noise level, as well as a reduction in environmental impacts, so it seems very probable that they will start to fill particular market niches as a replacement for vapor-compression technology in the future. [ABSTRACT FROM AUTHOR]

Thermoelastic cooling is a recently proposed, novel solid-state cooling technology. It has the benefit of not using high global warming potential (GWP) refrigerants which are used in vapor compression cycles (VCCs). Performance enhancements on a thermoelastic cooling prototype were investigated. A few novel design options aiming to reduce the cyclic loss were proposed. It was found that the maximum temperature lift increased from 6.6 K to 27.8 K when applying the proposed novel designs, corresponding to 0–152 W cooling capacity enhancement evaluated under 10 K water–water system temperature lift. In addition, a multi-objective optimization problem was formulated and solved using the genetic algorithm to maximize the system capacity and coefficient of performance (COP). With all the novel designs, the optimization could further enhance 31% COP, or 21% cooling capacity, corresponding to COP of 4.1 or 184 W maximum cooling capacity. [ABSTRACT FROM AUTHOR]

To avoid global warming potential gases emission from vapor compression air-conditioners and water chillers, alternative cooling technologies have recently garnered more and more attentions. Thermoelastic cooling is among one of the alternative candidates, and have demonstrated promising performance improvement potential on the material level. However, a thermoelastic cooling system integrated with heat transfer fluid loops have not been studied yet. This paper intends to bridge such a gap by introducing the single-stage cycle design options at the beginning. An analytical coefficient of performance (COP) equation was then derived for one of the options using reverse Brayton cycle design. The equation provides physical insights on how the system performance behaves under different conditions. The performance of the same thermoelastic cooling cycle using NiTi alloy was then evaluated based on a dynamic model developed in this study. It was found that the system COP was 1.7 for a baseline case considering both driving motor and parasitic pump power consumptions, while COP ranged from 5.2 to 7.7 when estimated with future improvements. [ABSTRACT FROM AUTHOR]

• Solution-treated Ti 50 Ni 48 Fe 2 and aged-hardened Ti 49.2 Ni 49.3 Fe 1.5 were investigated. • Ti 49.2 Ni 49.3 Fe 1.5 aged at 400 °C × 150 h exhibited the largest recoverable strain. • These alloys showed linear superelasticity after 1000 compression cycles. • Elastocaloric cooling of −4.1 to −7.0 °C at operating temperatures of −40–80 °C • Small temperature dependence (0.5 MPa/°C) of transformation stress was observed. The transformation and superelasticity characteristics of solution-treated Ti 50 Ni 48 Fe 2 and aged-hardened Ti 49.2 Ni 49.3 Fe 1.5 shape memory alloys during cyclic compressive deformation were investigated. The Ti 50 Ni 48 Fe 2 alloy could not be precipitation hardened, while the Ti 49.2 Ni 49.3 Fe 1.5 alloy, aged at 400 °C, was hardened by Ti 3 Ni 4 precipitates. During the cyclic deformation, the B2⇆R⇆B19′ transformation peaks broadened and spread to a large temperature span. At the same time, the superelasticity behavior became linear, and the associated elastocaloric cooling capacity decreased to a stable value. Among these samples, Ti 49.2 Ni 49.3 Fe 1.5 alloy aged at 400 °C for 150 h exhibited the largest recoverable strain in superelasticity and retained the largest cooling effect after 1000 deformation cycles. Furthermore, it showed elastocaloric cooling of −4.1 °C to −7.0 °C at operating temperatures of −40–80 °C. Experimental results revealed that B19′ transformation was suppressed significantly by cyclic deformation, and thus the transformation occurred in a wide temperature range of −160 to −50 °C. Additionally, the linear superelasticity exhibited a low slope of the Clausius–Clapeyron relation of about 0.5 MPa/°C. These features allow the alloys to exhibit superelasticiy and the elastocaloric effect over a wider temperature range. [ABSTRACT FROM AUTHOR]