Abstract
Thermal energy storage technologies through solid/liquid phase change materials (PCMs) use the
thermodynamic principles of melting and solidification to absorb and release thermal energy. In
the ideal case, this technology allows to charge and discharge relatively high amounts of thermal
energy at a constant, unique temperature. However, for most commercially available technicalgrade
solid/liquid PCMs melting and solidification cannot be assigned to a single, unique
temperature. Instead, the phase transition takes place over a temperature range in which solid and
liquid phases coexist. Moreover, supercooling sometimes causes hysteresis in the phase
transitions depending on the applied heating and cooling rates. These phenomena cause non-ideal
phase transition behaviour and generally reduce the applicability of the PCMs. PCM models
which can reproduce this non-ideal behaviour are crucial for the numerical analysis of the
charging and discharging operation of latent heat storages. This contribution presents a generic
workflow for the identification of phase transition models for industrial-grade solid/liquid PCMs.
Adopting a purely phenomenological approach models are directly identified from PCM heat
capacity measurement data. Thus, if the data contains information on temperature ranges with
coexisting phases and hysteresis in the temperature induced phase transitions these phenomena
are directly accounted for. The identified transition models predict liquid mass phase fractions
using PCM temperature as a model input. These models are then used to describe apparent
(effective) PCM properties in the phase transition temperature range, i.e. specific heat, density
and thermal conductivity. Applications of the workflow are presented for different commercial
PCMs from Climator Sweden AB. The effects of non-ideal phase transition behaviour on
absorption and release of heat in a latent thermal energy storage are discussed by simulation
studies.
Originalsprache | Englisch |
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Titel | Proceedings of EUROTHERM SEMINAR #112 |
Seitenumfang | 10 |
Publikationsstatus | Veröffentlicht - 2019 |
Research Field
- Efficiency in Industrial Processes and Systems