Modeling of phase change hysteresis during partial phase change with the “shift”-method

Abstract

For phase change materials (PCM) a difference between melting and crystallization temperature can occur, the so-called supercooling. For numerical modelling of this hysteresis effect, phenomenological approaches based on the experimentally determined enthalpy-temperature relations for melting and crystallization can be applied. It is challenging to model the behavior for partial phase transitions. The study presents a new phenomenological method, called the “shift”-method. It is derived especially but not only for PCMs with a multistage phase change during crystallization, like it can occur for microencapsulated PCMs. The method is verified by experimental results and compared to an existing approach called “curve-scale”-method. Partial melting and crystallization processes of a PCM composite are experimentally characterized with differential scanning calorimetry (DSC). Additionally, both methods are integrated in a Dymola Modelica model of a battery cooling system with the PCM composite and validated against experimental results. The normalized mean square error is used to determine the deviation between the experiments and the two methods. It is less than 1.7 % for both methods.