Calorimetric techniques for the evaluation of thermal efficiencies of shape memory alloys

The latent heat and entropy changes of NiTi shape memory effect (SME) alloys have been evaluated by three different calorimetric techniques; adiabatic calorimetry, differential scanning calorimetry and a Clapeyron analysis of isothermal stress-strain data. It is found that these techniques provide consistent estimates for the enthalpy and entropy to within 20% for NiTi and noble metal SME alloys. From published thermodynamic data for SME alloys, thermal efficiencies were calculated based on an ideal SME heat engine cycle. It was found that NiTi provides the maximum thermal efficiency with the highest temperature transformation range.

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