Dear colleagues,
I'm gonna ask a definition about phase change material for thermal energy storage.
What is the difference between the thermal stability and reliability of PCM?
Which one is characterized by TG analysis?
Thank you for your attention!
Bests, Xiaobin
Thermal Stability of Phase Change Material
in this link
Chapter Phase Change Materials and Their Applications
Long-term thermal and chemical reliability study of different organic phase change materials for thermal energy storage applications
in this page
Article Long-term thermal and chemical reliability study of differen...
Preparation, Thermal Properties and Thermal Reliability of Form-Stable Paraffin/Polypropylene Composite for Thermal Energy Storage
polypropylene (PP)
In the composite, paraffin acts as a PCM when PP is operated as supporting material. The composites prepared at different mass fractions of paraffin (50, 60, 70, 80, and 90 w/w%) by solution casting method were subjected to leakage test by heating the composites over the melting temperature of the PCM.
Article Preparation, Thermal Properties and Thermal Reliability of F...
More details in this link
Dear Prof. Gamal B. Abdelaziz , thank you for your valuable reply and papers.
I propose the following:
A PCM is thermally stable if its phase change temperature and latent heat remain the same along its life.
It is reliable if these physical characteristics remain within a useful domain, and if it causes no harm.
Thermogravimetry (TG) measures the variation of mass with temperature, so the mass loss when evaporation occurs, but measures no change for solid-liquid PCMs. Differential temperature analysis (DTA) can measure the temperatures at which the phase changes when the temperature is increasing or decreasing, as well as the latent heat if the calorimetry is also measured.
Dear Prof. Claude-Alain Roulet ,thank you for your kind response. In the field of polymer, thermal stabiblity is defined as the ability of polymeric material to resist the action of heat, which is usually tested by TG. Is that what you mean?
would Thermogravimetry indicate compositional change if, for example, an organic PCM undergoes decomposition at excessive temperature or in an oxygenating environment? These will obviously also be reflected in Latent heat reduction and possibly phase change temperature shift.
I agree with Claude-Alain Roulet 's definition. Stability is about relevant properties staying relatively constant (or cyclicly consistent) so that operation is repeatable. Those properties for TES would necessarily include latent heat capacity and phase change temperature, but also possibly thermal conductivity and sensible heat capacity. mass loss would be reflected in the capacity change.
Reliability means the likelihood that the materiel or PCM system continues to perform the desired function. Degradation due to instability can make something unreliable in the long term. A material with a high degree of supercooling could be reliable if that is consistent and within design margins, but it would be unreliable if it the supercooling magnitude is stochastic, unpredictable, and might exceed design margins. Additionally, the container reliability would include it's ability to withstand any cyclical expansion pressures, not corrode overtime in contact with the melting/solidifying PCM. Heat-absorption reliability may include accounting for the location of any contraction voids or delaminations that form over repeated melting cycles, etc.
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