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Numerical study on the melting thermal characteristics of a microencapsulated phase change plate

ABSTRACT The melting thermal characteristics of a microencapsulated phase change material (MEPCM) plate under constant heat flux are numerically investigated. The effective property relations of the MEPCM plate related to the parameters of base materials are first established and verified by the measured thermal properties of 10 samples. A one-dimensional phase change thermal model based on the enthalpy method is built, and the predicted results are also verified with test data. The temperature profile and phase interface movement in the MEPCM plate are discussed, and the effects of Stefan number, phase change temperature range, particle and core fraction, and additive fraction are also analyzed. Three states of solid, mushy, and fluid phases of phase change material (PCM) core divide the melting process of the MEPCM plate into five stages as follows: Fo ≤ 0.1, 0.1 < Fo ≤ 0.2, 0.2 < Fo ≤ 0.9, 0.9 < Fo ≤ 1.2, and Fo ≥ 1.2. The time point of regular regime for heat transfer in the MEPCM plate is Fo = 0.2. The addition of conductivity additive homogenizes the temperature profile in the MEPCM plate. Under the combined effects of thermal diffusivity and Ste number, an optimum additive fraction exists for the MEPCM plate to achieve the minimum melting completion time or the maximum latent storage efficiency.