EFFECT OF FORCED CONVECTION AND COMPRESSIBILITY ON TRANSIENT MELTING BEHAVIOR OF PCM IN A CAVITY

Date

2025-8-27

Author

Farshineh Adl, Houman

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Improving heat transfer rates enhances the performance of devices that dissipate excess heat or require heat storage. Among the available options, phase change material (PCM) possesses advantageous thermal properties but exhibits comparatively slow melting rates, a limitation that the present study aims to mitigate. Both experimental and numerical studies are conducted using a cavity (generic domain) filled with PCM to assess forced convection induced by mixing the liquid PCM at rotational speeds of 5, 25, and 100 𝑟𝑝𝑚. The experimental work focuses on the effect of forced convection, while the numerical analyses evaluate the compressibility effect. In numerical analyses, the enthalpy-porosity model is applied, utilizing either the Boussinesq approximation or the volume of fluid (VoF) method. The VoF method models the compressibility effect, enabling observation of the close contact melting (CCM) phenomenon. At higher rotational speeds, the melting duration is reduced by approximately 22%, to 32 hours, and the liquid fraction at steady state is increased by as much as 14%, resulting in complete PCM melting compared to the non rotating case. Mixing also decreased temperature gradients inside the domain, lowering peak temperature from 68°𝐶 to 45°𝐶. At lower rotational speeds, melting duration is decreased by only about 10% with a negligible change in liquid fraction at steady state. The effect of compressibility on PCM melting characteristics, when CCM is observable, is studied numerically. Using the Boussinesq approximation instead of the VoF method results in an unrealistic overestimation of the melting time by a factor of eight.

Subject Keywords

phase change material, forced convection, melting time, compressibility

URI

https://hdl.handle.net/11511/115592

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Graduate School of Natural and Applied Sciences, Thesis