(36d) Phase Change Heat Transfer in Cylinders

Phase change heat transfer is an important phenomena in energy storage systems and has also solar applications.In this work, freezing of phase change materials(PCM) in copper cylinders would be presented.The freezing process with super heat in the melt is significantly affected by free convection resulting in lower heat transfer rates compared to the absence of initial super heat.As the orientation of test cylinder influences the convective heat transfer coefficients,our experimental study included both horizotal and vertical orientations of test cylinders. Two PCMs namely n-octadecane(MP 28C) and paraffin wax(MP60C)were used in the study.Range of parameters were: L/d:1 to 5,initial superheat:2 to 25C,temperature drop across frozen layer:2 to 28C,volume of PCM:50cc to 1000cc. Cooling was affected by immersion in isothermal water bath(accuracy<1C).Experimental data of radial and axial temperature distributionns in PCM were obtained with pt-100 sensors and frozen mass vs time data were obtained by direct weighing method.A discussion of results of temperature distribution and freezing rate variation with time and comparison with mathematical models avalable in literature would be presented.