Phenomenological model for first-order elastocaloric materials

Bachmann, Nora; Fitger, Andreas; Unmüßig, Sabrina; Bach, Dieter; Schäfer-Welsen, Olaf; Koch, Thomas; Bartholomé, Kilian

doi:10.1016/j.ijrefrig.2022.01.009

Cited by 11 publications

(5 citation statements)

References 20 publications

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“…The maximum material efficiency was reached at a = 0.5 and amounted to η mat = 16%. The values for ∆T hys = 11.9 K and ∆T ad = 9.0 K were determined using the material model [24].…”

Section: Discussionmentioning

confidence: 99%

“…In this block, thermal and fluid data are combined, resulting in a transition between the liquid and gaseous states of the fluid. The material behavior was implemented using the material model previously published in [24] with the following ECM parameters: T 0 = 273.9 K, temperature at maximum heat capacity with no applied field; ∆s iso,max = 42.7 J/(kg K), maximum isothermal entropy change; c 0 = 663.6 J/(kg K), heat capacity far from the transformation peak; α = 26.8 K, width of the heat capacity peak; and β = 0.0845 K/MPa, the multiplicative inverse of the Clausius-Clapeyron coefficient [24].…”

Section: System Simulationmentioning

confidence: 99%

“…To model the materials' behavior, a thermodynamically consistent model based on an approximation of the heat capacity curve by a Cauchy-Lorentz distribution was used. The adiabatic temperature change and dissipative energy of the material can be analytically derived from this equation and expressed as a function of mechanical stress and temperature [24]. Non-measurable input variables such as thermal resistance in the cooling system were determined in advance using an analytical model as described below.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of an Elastocaloric Cooling System for Determining Efficiency

et al. 2022

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When it comes to covering the growing demand for cooling power worldwide, elastocalorics offer an environmentally friendly alternative to compressor-based cooling technology. The absence of harmful and flammable coolants makes elastocalorics suitable for energy applications such as battery cooling. Initial prototypes of elastocaloric systems, which transport heat by means of thermal conduction or convection, have already been developed. A particularly promising solution is the active elastocaloric heat pipe (AEH), which works with latent heat transfer by the evaporation and condensation of a fluid. This enables a fast and efficient heat transfer in a compression-based elastocaloric cooling system. In this publication, we present a simulation model of the AEH based on MATLAB-Simulink. The model showed very good agreement with the experimental data pertaining to the maximum temperature span and maximum cooling power. Hereby, non-measurable variables such as efficiency and heat fluxes in the cooling system are accessible, which allows the analysis of individual losses including the dissipation effects of the material, non-ideal isolation, losses in heat transfer from the elastocaloric material to the fluid, and other parasitic heat flux losses. In total, it can be shown that using this AEH-approach, an optimized system can achieve up to 67% of the material efficiency.

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“…The maximum material efficiency was reached at a = 0.5 and amounted to η mat = 16%. The values for ∆T hys = 11.9 K and ∆T ad = 9.0 K were determined using the material model [24].…”

Section: Discussionmentioning

confidence: 99%

Section: System Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling of an Elastocaloric Cooling System for Determining Efficiency

et al. 2022

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“…This FOM can also be expressed in the form of the COP of the caloric material COP mat = qc q diss [26]:…”

Section: Caloric Cooling Cyclesmentioning

confidence: 99%

On the efficiency of caloric materials in direct comparison with exergetic grades of compressors

Schipper,

Bach,

Mönch

et al. 2023

J. Phys. Energy

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Efficiency improvements in heat pump can drastically reduce global energy demand. Caloric heat pumps are currently being investigated as a potentially more efficient alternative to vapor compression systems. Caloric heat pumps are driven by solid-state materials that exhibit a significant change in temperature when a field is applied, such as a magnetic or an electric field as well as mechanical stress. For most caloric materials, the phase transition results in a certain amount of power dissipation, which drastically impacts the efficiency of a caloric cooling system. The impact on the efficiency can be expressed by a figure of merit (FOM), which can directly be deduced from material properties. This FOM has been derived for 36 different magneto-, elasto-, electro and barocaloric material classes based on literature data. It is found that the best materials can theoretically attain second law efficiencies of over 90%. The FOM is analogous to the isentropic efficiency of idealized compressors of vapor compression systems. The isentropic efficiency can thus be directly linked to the theoretically achievable efficiency of a compressor-based refrigeration system for a given refrigerant.In this work a theoretical comparison is made between efficiency of caloric heat pumps and vapor compression systems based on the material losses for the caloric heat pump and the efficiency of the compressor for vapor compression systems. The effect of heat regeneration is considered in both cases. In vapor compression systems, the effect of the working fluid on the efficiency is also studied.

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“…[51][52][53][54][55][56][57][58][59][60][61][62][63][64] For an actual cooler or heat pump, it always operates at a finite temperature lift between the hot side (heat sink) with a temperature of T h and the cold side (heat source) with a temperature of Tc. [65][66][67][68][69][70][71][72][73][74][75][76][77] Comprehensive characterizations of the superelastic and elastocaloric effects of NiTi and NiTi-based SMAs in the desired temperature range are vital to the development of this cutting-edge technology for green heating and air-conditioning.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the temperature-dependent superelastic and elastocaloric effects of a NiTi tube under compression at 293–330 K

Cheng,

Yan,

et al. 2024

AIP Advances

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Comprehensive characterizations of the superelastic and elastocaloric effects of NiTi and NiTi-based shape memory alloys (SMA) in the operation temperature region are highly desirable for using them in elastocaloric coolers with a large temperature lift. In this article, we report the superelastic and elastocaloric effects of a commercially available superelastic polycrystalline NiTi SMA tube with an outer diameter of 5 mm and a wall thickness of 1 mm between 293 and 330 K. The NiTi tube sample was subjected to a training of 250 cycles to stabilize its superelastic and elastocaloric effects. We observed that temperature dependencies existed for both superelastic and elastocaloric effects of the NiTi tube, and stress–strain curves differed much between isothermal and adiabatic loading conditions. The largest temperature rise and temperature drop measured at 293 K under an applied strain of 3.66% and a strain rate of 0.1 s−1 during loading and unloading were 21 and 11 K, respectively. The loading conditions (loading function and holding time) also impacted the superelastic effect of the NiTi tube. We identified two major reasons for the irreversibility of the adiabatic temperature change: the hysteresis heat dissipation and the temporary residual strain after unloading, and they affected the cooling performance of the elastocaloric cooler in different ways. We investigated the dependencies of the superelastic and elastocaloric effects on the maximum applied strain and the temperature distribution on the NiTi tube during loading and unloading. The results are beneficial to the modeling of elastocaloric coolers with large temperature lifts.

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Phenomenological model for first-order elastocaloric materials

Cited by 11 publications

References 20 publications

Modeling of an Elastocaloric Cooling System for Determining Efficiency

Modeling of an Elastocaloric Cooling System for Determining Efficiency

On the efficiency of caloric materials in direct comparison with exergetic grades of compressors

Characterization of the temperature-dependent superelastic and elastocaloric effects of a NiTi tube under compression at 293–330 K

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