Experimental and numerical investigations of thermal performance enhancement in a latent heat storage heat exchanger using bifurcated and straight fins

In this paper, the effects of applying straight and bifurcated fin configurations on melting behavior of paraffin inside the shell-and-tube heat exchangers are both experimentally and numerically investigated. Three different fin arrangements for each of the fin configurations were considered: (a) cross arrangement, (b) diagonal cross arrangement and (c) arranged evenly at the lower half of the heat exchanger. The evolution of the melt front was photographed to obtain the instantaneous melt fractions and gain a better insight into the effect of fin configuration on the melting process of phase change material under different Rayleigh and Stefan numbers. The impacts of fin length and thickness on the thermal performance of the heat exchangers were also investigated while the mass of fins for all cases was kept constant. It was found that the bifurcated fin configuration outperforms the straight fin configuration. Also, the fin arrangement showed a significant effect on the melting process. Numerical results revealed that the optimum fin arrangement depends on the fin length which was more pronounced when the fins located at the lower half of the annulus. For charging temperature of 95 °C (Ste = 1.08, Ra = 1.73 × 10⁶), the maximum melting time reductions of bifurcated fin heat exchangers with dimensionless fin lengths of 0.51 and 0.89 mm, compared to those of the straight fin heat exchangers, were 19.5% for the (c)-type fin arrangement and 61.6% for the (b)-type fin arrangement, respectively.