Unsteady heat transfer of NEPCM during freezing in a channel

Transient problem of freezing phenomena within a system including two wavy PCM layers has been analyzed in this research. Existence of three air cold flow duct among the PCM layers makes it possible to observe solidification of paraffin. The selected PCM is RT30 and Al 2 O 3 nano-powders were added to remove the limitation of paraffin. Finite volume method was applied for simulation of this unsteady phenomenon, and to model turbulent flow of air, k – ɛ approach was selected. Verification with experimental article proves the nice accuracy of code. Concentration of alumina and amplitude of wavy layers were assumed as variable factor. At beginning of freezing, temperature of whole zones is 305.15 K and inlet air has temperature of 285.15 K. As paraffin solidifies, heat releases and makes air warmer. The worst state in view of time is a = 5 mm and φ = 0.04 which takes 19193 s to achieve full solidification. The minimum required time for freezing occurs at a = 20 mm and φ = 0.04 which takes 11479 s. At t = 150 s, augment of amplitude leads to 25.27% augmentation in solid fraction and 2.5% reduction in temperature. Also, at same time stage, adding nanoparticles makes temperature to reduce about 0.42% while solid fraction augments about 1.96%. With augment of amplitude, required time decreases about 36.71% and 35.82% when φ = 0 and 0.04, respectively. Freezing time declines about 5.49% with addition of nano-powders when a = 20 mm.