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<p>We re-evaluate the thermodynamics of a generic elastocaloric (EC) device based on shape memory alloys (SMA) operating between a hot and a cold reservoir, acting either as a heat pump or as a cooling device. The work is motivated by the noticeable discrepancies in the literature regarding the key parameters used to evaluate the coefficient of performance (COP) of these devices. We show that the COP depends on the temperatures of both the cold and hot reservoirs, <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40830_2025_536_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="20" /> </InlineMediaObject> <EquationSource Format="TEX">\({T}_{\text{C}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>C</mtext> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40830_2025_536_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="20" /> </InlineMediaObject> <EquationSource Format="TEX">\({T}_{\text{H}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mtext>H</mtext> </msub> </math></EquationSource> </InlineEquation>, on the ratio of the SMA material specific heat to entropy of transformation, <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40830_2025_536_Article_IEq3.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="54" /> </InlineMediaObject> <EquationSource Format="TEX">\({c}_{p}/\Delta {s}_{\text{tr}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>c</mi> <mi>p</mi> </msub> <mo stretchy="false">/</mo> <mi mathvariant="normal">Δ</mi> <msub> <mi>s</mi> <mtext>tr</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation>, and on the hysteresis, <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40830_2025_536_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Delta {T}_{\text{hys}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <msub> <mi>T</mi> <mtext>hys</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation>, associated with the stress-induced martensitic transformation involved. The effect of heat recovery (regeneration) efficiency on COP is also evaluated. In addition, we have reviewed the concept of adiabatic temperature change, <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40830_2025_536_Article_IEq5.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="37" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Delta {T}_{\text{ad}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Δ</mi> <msub> <mi>T</mi> <mtext>ad</mtext> </msub> </mrow> </math></EquationSource> </InlineEquation>, including its experimental determination and supporting the analysis with our own measurements. Material selection charts are proposed as a useful guide for the conceptual design of EC devices. They emphasize the importance of correctly considering the operating parameters of the system, in addition to the specific SMA properties mentioned above.</p>

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New Insight into the Coefficient of Performance and Related Material Indices of Merit for the Selection of Shape Memory Elastocaloric Materials

  • 期刊论文

  • 发表日期：

    2025年5月5日

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  • Juan Delmastro,
  • Ignacio Bustos,
  • Gastón Alonso,
  • Alejandro Yawny

摘要

We re-evaluate the thermodynamics of a generic elastocaloric (EC) device based on shape memory alloys (SMA) operating between a hot and a cold reservoir, acting either as a heat pump or as a cooling device. The work is motivated by the noticeable discrepancies in the literature regarding the key parameters used to evaluate the coefficient of performance (COP) of these devices. We show that the COP depends on the temperatures of both the cold and hot reservoirs, \({T}_{\text{C}}\) T C and \({T}_{\text{H}}\) T H , on the ratio of the SMA material specific heat to entropy of transformation, \({c}_{p}/\Delta {s}_{\text{tr}}\) c p / Δ s tr , and on the hysteresis, \(\Delta {T}_{\text{hys}}\) Δ T hys , associated with the stress-induced martensitic transformation involved. The effect of heat recovery (regeneration) efficiency on COP is also evaluated. In addition, we have reviewed the concept of adiabatic temperature change, \(\Delta {T}_{\text{ad}}\) Δ T ad , including its experimental determination and supporting the analysis with our own measurements. Material selection charts are proposed as a useful guide for the conceptual design of EC devices. They emphasize the importance of correctly considering the operating parameters of the system, in addition to the specific SMA properties mentioned above.