Simple Heat Transfer Experiment To Evaluate The Solid/Liquid Phase Change Thermal Energy Storage System

A detailed experimental freezing study, designed for undergraduate students, has been carried out to evaluate the heat transfer performance of a solid/liquid phase-change thermal energy storage system. The test vessel system, experimental procedure and results, and analytical solutions are discussed. The phase-change material (PCM) is contained in a vertically oriented test cylinder that is cooled at its outside boundary, resulting in radially inward freezing. Detailed quantitative time-dependent volumetric temperature distributions and freeze-front motion and shape data were experimentally obtained. To fully understand the behavior of the eicosane, four freezing tests were performed with different temperature set points as low as 10 degrees C.In the analysis, results of a test in which molten eicosane, initially at 50 degrees C, was solidified and brought to a fmal temperature of 10 degrees C are presented. In the freezing case study, a mathematical model based on a one-dimensional analysis, which considered heat conduction as the only mode of heat transfer was developed. The phase-change medium, 99% pure eicosane (C20H42) was chosen as the PCM. Eicosane is desirable because its fusion temperature is just slightly higher than ambient temperature (36.5 degrees C), which is convenient for phase-change experimentation. Low-temperature heating can be used to melt the PCM and ambient-temperature cooling can be used to re-freeze it.To evaluate the inward radius of fusion, several analytical and experimental approaches were considered. These approaches were (1) experimental method; (2) conduction model; (3) integral method; and (4) cumulative heat transfer method. Comparison of these methods reveals excellent agreement. In most cases, the heat transfer estimated from the freezing-front analysis was slightly higher than the heat transfer evaluated from the time-series data. The largest discrepancy occurs at fifty minutes into the experiment (10.7%).