An investigation of measurement method and phase change in a latent heat energy storage device

Exploring uses of two-phase mixtures as a way to store peak solar energy for off-peak usage is a novel approach that has been gaining attention in recent years to address the issues tied to solid fuel dependence. This research explores a “solar salt” mixture (40%wt KNO3 and 60%wt NaNO3) in an aluminum enclosure under two test conditions: conduction enhancement and no conduction enhancement. The central aim is to develop an understanding of thermal distributions and melt developments as the system moves from room temperature to 300 oC. Thermal pattern development is explored by experimentally observing a 2-D temperature field at 8 co-planar points, comprised of 3 radial positions with complementary circumferential measurements, using thermocouples. The instrument array is traversed to three different axial positions where collected data is compared with results from a numerical solver. Results find three important details. First, the melt pattern of the fin experiments show quicker rates of melting after the onset of melt at the bottom of the enclosure. Second, the spatial effects of the instrumentation influence the presence of thermal phenomena. Lastly, approximations of the salts behavior using numerical simulations are supported in identifying phases of melt development.