Novel Experimental Approach to Determine Elastocaloric Latent Heat

Michaelis, Nicolas; Schütze, Andreas; Welsch, Felix; Kirsch, Susanne‐Marie; Seelecke, Stefan

doi:10.1007/s40830-019-00249-y

Cited by 8 publications

(5 citation statements)

References 18 publications

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“…The electrically induced temperature change is then matched with the elastocaloric temperature change by adjusting the electric power amplitude passing through the wire in an iterative process. Power amplitude and pulse duration subsequently allow for a quantitative determination of the energy during the process, which is a very good approximation to the latent heats from the mechanical loading process [46,51].…”

Section: Caloric Characterizationmentioning

confidence: 99%

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A unified approach to thermo-mechano-caloric-characterization of elastocaloric materials

Louia,

Michaelis,

Schütze

et al. 2023

J. Phys. Energy

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This paper presents a novel approach to characterizing the relevant mechanical, thermal and caloric properties of elastocalorics material in a single testing device. Usually, tensile experiments are performed to determine the rate- and process-depending stress/strain behavior of Nickel-Titanium-based shape memory alloys and potentially other elastocaloric materials made from metallic alloys. These tests are relevant for, e.g., characterization of hysteresis properties and subsequent calculation of mechanical work input. In addition, simultaneous observation with an infrared camera is useful to understand temperature evolution and maximum temperature changes achievable during the loading/unloading process. Characterization of the caloric properties of the materials determines latent heats and, together with the mechanical work, also the material coefficient of performance. It is typically carried out via Differential Scanning Calorimetry (DSC), which is performed in a separate device and requires a second experiment with different types of samples. Furthermore, DSC measurements do not reflect the way mechanically induced phase transformations trigger the release and absorption of latent heats as it is the case for elastocalorics. In order to provide a more consistent understanding of the relevant elastocaloric material properties, we here present a novel method that a) allows for a systematic determination of load-dependent latent heats and b) introduces a comprehensive testing setup and suitable testing routine to determine the mechanical, thermal and caloric parameters in the same experimental device and with the same sample, thus greatly simplifying the overall procedure.

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Section: Caloric Characterizationmentioning

confidence: 99%

“…R C stands for the total resistance of the clamps that needs to be taken into account. The value of R S is chosen to be R S = 0.22 Ω, the value of R C is measured as R C = 20 mΩ [51].…”

Section: Caloric Characterizationmentioning

confidence: 99%

A unified approach to thermo-mechano-caloric-characterization of elastocaloric materials

Louia,

Michaelis,

Schütze

et al. 2023

J. Phys. Energy

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“…In both cases, the transformation is accompanied by a thermodynamic irreversibility [44,45] that manifests itself as temperature and stress hysteresis (more details about the phase transformation can be found elsewhere [46]). In superelasticity, when the austenite is mechanically loaded, it transforms to the martensite (forward transformation) and the latent heat of the transformation is released [47]. Upon unloading, the opposite occurs (reverse transformation) and the latent heat is absorbed.…”

Section: The Basics Of the Elastocaloric Effect (Martensitic Transfor...mentioning

confidence: 99%

From the elastocaloric effect towards an efficient thermodynamic cycle

et al. 2022

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In recent years, elastocaloric cooling technology has been considered as one of the most promising alternatives to vapor compression technology. Given that elastocaloric technology is only in the early stages of development, a uniform method for evaluating the elastocaloric effect has not yet been established, and the thermodynamics of different elastocaloric cooling cycles have not yet been studied in detail. Therefore, the main goal of this work is to investigate these two important areas. Here, multiple thermodynamic cycles were studied, focusing on the parameters of the holding period of the cycle, which is essential for heat transfer between the elastocaloric material and the heat sink/source. The cycles were applied to commercially available superelastic thin-walled NiTi tubes under compressive loading and a thin NiTi wire under tensile loading. Isostress cycles with constant stress throughout the holding period, isostrain cycles with constant strain throughout the holding period and no-hold cycles (without a holding period) were studied across multiple stress/strain ranges. Based on the experimental results, a previously developed phenomenological model was applied to better understand and further evaluate the different cycles. The results revealed that the applied thermodynamic cycle significantly affects the thermomechanical response and thus the cooling/heating efficiency of the elastocaloric material. We show that by using isostress cycles and partial transformations, a Carnot-like thermodynamic cycle with improved heating/cooling efficiency can be generated. By applying the isostress cycles, an adiabatic temperature change of 30.2 K was measured, which is among the largest directly measured reproducible adiabatic temperature changes reported for any caloric material to date. Ultimately, this study intends to serve as a basis for establishing a uniform method for evaluating the elastocaloric effect in different materials that would allow for reliable and accurate one-to-one comparison of the reported results in the rapidly growing field of elastocalorics.

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“…In experiments without vacuum the convective heat transfer to the surrounding fluid in for example, air has to be considered. This behavior can also be used to characterize the material parameters like heat transfer coefficient, heat conductivity and latent heats, as shown in [55,56,79]. Additional applications in material science are the characterization of shape memory alloys [20,43,65,68], the failure analysis of components and structures [10] or the plastic deformation detection [62].…”

Section: Introductionmentioning

confidence: 99%

Applicability of correlated digital image correlation and infrared thermography for measuring mesomechanical deformation in foams and auxetics

et al. 2022

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Cellular materials such as metal foams or auxetic metamaterials are interesting microheterogeneous materials used for lightweight construction and as energy absorbers. Their macroscopic behavior is related to their specific mesoscopic deformation by a strong structure‐property‐relationship. Digital image correlation and infrared thermography are two methods to visualize and study the local deformation behavior in materials. The present study deals with the full‐field thermomechanical analysis of the mesomechanical deformation in Ni/PU hybrid foams and Ni/polymer hybrid auxetic structures performing a correlative digital image correlation and infrared thermography. Instead of comparing and correlating only the primary output variables of both methods, strain and temperature, also strain rates and temperature rates occurring during deformation were compared. These allow for a better correlation and more conclusive results than obtained using only the primary output variables.

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Novel Experimental Approach to Determine Elastocaloric Latent Heat

Cited by 8 publications

References 18 publications

A unified approach to thermo-mechano-caloric-characterization of elastocaloric materials

A unified approach to thermo-mechano-caloric-characterization of elastocaloric materials

From the elastocaloric effect towards an efficient thermodynamic cycle

Applicability of correlated digital image correlation and infrared thermography for measuring mesomechanical deformation in foams and auxetics

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