Identification of Phase Fraction–Temperature Curves from Heat Capacity Data for Numerical Modeling of Heat Transfer in Commercial Paraffin Waxes

Tilman Barz, Johannes Krämer and Johann Emhofer
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Tilman Barz: AIT Austrian Institute of Technology GmbH, Giefingasse 2, 1210 Vienna, Austria
Johannes Krämer: AIT Austrian Institute of Technology GmbH, Giefingasse 2, 1210 Vienna, Austria
Johann Emhofer: AIT Austrian Institute of Technology GmbH, Giefingasse 2, 1210 Vienna, Austria

Energies, 2020, vol. 13, issue 19, 1-20

Abstract: The area-proportional baseline method generates phase fraction–temperature curves from heat capacity data of phase change materials. The curves describe the continuous conversion from solid to liquid over an extended temperature range. They are consistent with the apparent heat capacity and enthalpy modeling approach for the numerical solution of heat transfer problems. However, the curves are non-smooth, discrete signals. They are affected by noise in the heat capacity data and should not be used as input to continuous simulation models. This contribution proposes an alternative method based on spline approximation for the generation of consistent and smooth phase fraction–temperature, apparent heat capacity–temperature and enthalpy–temperature curves. Applications are presented for two commercial paraffins from Rubitherm GmbH considering heat capacity data from Differential Scanning Calorimetry and 3-layer-calorimetry. Apparent heat capacity models are validated for melting experiments using a compact heat exchanger. The best fitting models and the most efficient numerical solutions are obtained for heat capacity data from 3-layer-calorimetry using the proposed spline approximation method. Because of these promising results, the method is applied to melting data of all 44 Rubitherm paraffins. The computer code of the corresponding phase transition models is provided in the Supplementary Information.

Keywords: solid–liquid phase transition; phase fraction–temperature curves; paraffin heat capacity data; numerical modeling; apparent heat capacity method (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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