A numerical study on control mechanism of heat transfer in a double pipe PCM heat exchanger by changing eccentricity

The thermal analysis of a double pipe phase change material heat exchanger is studied numerically. The study is done for three cases as; a) Case A: a melting process when inner pipe is maintained at a constant temperature higher than melting point, b) Case B: a solidification process when the inner pipe temperature is constant but less than melting temperature, and c) Case C: for a cyclic thermal storage when the inner pipe surface temperature periodically changes between temperatures of Cases A and B. The aim of this study is to find the optimum position of the inner pipe for each studied cases and to investigate the differences in heat transfer mechanism of the above cases for various Rayleigh numbers. The obtained results show that for Case A, the best position of the inner pipe depends on Rayleigh number, but the bottom region provides the shortest melting time for Ra > 10(5). For the Cases B and C, the center must be preferred for all Reynolds numbers since the conduction heat transfer controls the process. In spite of many reported studies in literature, it is better to study on the enhancement of heat transfer for solidification rather than melting process.