Solid-liquid phase-change thermal storage and release behaviors in a rectangular cavity under the impacts of mushy region and low gravity

• Published in: International journal of heat and mass transfer 2019-03, Vol.130, p.1120-1132
• Main Authors: Hong, Yuxiang, Ye, Wei-Biao, Du, Juan, Huang, Si-Min
• Format: Article
• Language: English
• Subjects: Acceleration; Computer simulation; Enthalpy; Enthalpy-porosity method; Gravitation; Gravitational acceleration; Heat transfer; Latent heat storage/release; Liquid phases; Mathematical models; Mushy region; Mushy zones; Paraffin wax; Phase change materials; Porosity; Thermal storage; Thermodynamics
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2018.11.024

“Porosity function”, A(ϕ), which makes the momentum equation in the mushy zone “mimic” the Carman-Kozeny equation for fluid flow in a porous media, is determined by a mushy zone constant, C, and PCM liquid fraction, ϕ. On the other hand, the thermal storage/release processes may be occurred in low-gravitational situations with gravity acceleration, g < 9.81 m s−2, on the moon (g/6) for example. Therefore, the work deals with the validated numerical modeling of the thermal storage/release behaviors of paraffin wax in a partially thermal active rectangular cavity, and directs at the influences of mushy zone constant (shown in figures a1, a2) as well as gravitational acceleration (shown in figures b1, b2). It is found that the mushy zone constant and gravitational acceleration significantly influence the thermal storage behaviors, while they conduct very limited impacts on the thermal release process. [Display omitted] •Mushy zone constant (C) and gravitational acceleration (g) are examined.•C and g are significant influence thermal storage while limited on thermal release.•C should be examined when enthalpy-porosity method is used for solid-liquid change.•The proposed equations regarding how to calculate C are outlined and commented. The work aims to address the effects of mushy zone constant (1 × 104 ≤ C ≤ 1 × 108 kg m−3 s−1) and gravitational acceleration (1.635 ≤ g ≤ 9.810 m s−2) on the thermal storage/release behaviors of paraffin wax (phase change material, PCM), by performing numerical investigations in a rectangular cavity with partially thermal active walls. The enthalpy-porosity method is employed to simulate the solid–liquid phase-change process and flow evolution at the PCM interface. The numerical model is validated by the published literature data. It is confirmed that the thermal storage behaviors are significantly influenced by the mushy zone constant and gravitational acceleration. PCM liquid fraction is essentially increased as decreased in mushy zone constant and increased in gravitational acceleration, with maximum discrepancies are reached 88%. However, very limited impacts are conducted on the thermal release process with maximum PCM liquid fraction discrepancy only 2%. Furthermore, the proposed equations regarding how to calculate the value of mushy zone constant are also outlined and commented. Therefore, proper examination and verification for mushy zone constant is very important and necessary before solid–liquid phase-change thermal