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The objective of this work is to model the heat transfer coefficient between an immersed surface and fixed and bubbling fluidized beds of granular phase change material (PCM). The model consists of a two-region model with two different voidages in which steady and transient conduction problems are solved for the fixed and fluidized bed cases, respectively. The model is validated with experimental data obtained under fixed and fluidized conditions for sand, a common material used in fixed and fluidized beds for sensible heat storage, and for a granular PCM with a phase change temperature of approximately 50 degrees C. The superficial gas velocity is varied to quantify its influence on the convective heat transfer coefficient for both the materials. The model proposed for the PCM properly predicts the experimental results, except for high flow rates, which cause the contact times between the surface and particles to be very small and lead the model to overpredict the results.