Multiple Optical Characterization Of A Solid/Liquid Material

Abstract

Various industrial configurations use Phase Change Materials (PCM) for thermal management. Their use generates complex flows that must be studied and characterized to better understand the phase-change mechanisms and to help model development. In particular, the works considering large containers where turbulent effects are encountered are poorly addressed in the literature. The present study proposes the experimental analysis of PCM flows with a simultaneous flow and energetic characterization. Heat and mass transfer are analyzed in a large (0.4 meter) cubic volume undergoing various lateral temperature conditions. 2-dimensional fields of velocities by a Particle Image Velocimetry (PIV) technique and temperature by thermocouples (TC) scanning and by Background-Oriented Schlieren (BOS) are measured. The measurement methodology highlights the local transfer as reflected by the Nusselt number for the two latter techniques. The local Nusselt numbers are also integrated and compared to a global Nusselt assessed by the heat transfer through the hot wall regulating system. In this study, the different techniques with their theoretical approaches and the experimental setup are described. The conditions and the conducted procedure of the tests are detailed. The results of local measurements for two particular temperature configurations are given. The global heat transfer and the global Nusselt number are also provided as a function of the Rayleigh number and the solid fraction. The results and the techniques are discussed. The results corresponding to various Rayleigh numbers form a database that is used to understand phenomena in large PCM containers and validate numerical models involving melting phenomena.