Paraffins as phase change material in a compact plate-fin heat exchanger - Part II: Validation of the “curve scale” hysteresis model for incomplete phase transitions

Abstract

Technical-grade and mixed solid–liquid phase change materials (PCM’s), such as commercial paraffins, can show a complex non-isothermal phase transition behavior, possibly with hysteresis and supercooling, two-step transitions and asymmetric phase transition peaks. Phenomenological modeling approaches can use data-driven methods to derive phase transition models represented by enthalpy–temperature or apparent heat capacity–temperature curves. These curves are then linked with simulation models for heat transfer in thermal storages with PCM’s. If the phase change is significantly affected by hysteresis, different curves might be tracked either for heating or for cooling. This “curve track” modeling approach is straightforward and easy to implement. However, it shows a poor performance considering conditions with interrupted phase change, which are relevant for the partial charging and discharging operation of thermal storages. This contribution presents a novel so-called “curve scale” model. Its superior performance is proved for three commercial paraffins and experiments with 31 interrupted phase change scenarios.