Effect of Non-Uniform Heat Transfer Coefficient on Melting of Phase Change Materials in Horizontal Circular Cylinders

Abstract

Effect of non uniform heat transfer coefficient around the surface of horizontal circular cylinders on melting of phase change material (PCM) filled in the cylinders was studied by experiment and numerical analysis. Results of the numerical analysis performed on the basis of the uniform and non-uniform heat transfer coefficient with and without consideration of natural convection were compared with the experiment with water and tetradecane as PCM and acrylic resin and copper as cylindrical materials. Results show that heat conduction with the non-uniform heat transfer coefficient is dominant for the case of small cylinders. Effect of natural convection can not be neglected for the diameter more than 20 mm. Effect of the non-uniform heat transfer coefficient on flow of the natural convection was increased with increase in the diameter in conduction-dominant region. For case of acrylic cylinder. However the difference in the melting time is at most 5%. In natural convection dominant region, the diameter larger than 40 mm, the effect of the non-uniform heat transfer coefficient on the natural convection was reduced with increase in Rayleigh number in inner cylinder. For case of the copper cylinder, wall temperature was almost uniform in spite of the non-uniform heat transfer coefficient. Therefore, the effect of the non-uniformity in the heat transfer coefficient can be neglected for circular cylinders of copper and large diameter.