Effect of inclination angles on heat transfer characteristics of solid and perforated spiral finned heat exchangers

Abstract

Cylinder models integrated with solid/perforated spiral fins are a major direction for heat transfer enhancement in shell-and-tube latent heat exchangers. In practical engineering applications of this system, there exists an operational requirement for different orientations. To investigate how the orientation affects the melting/solidification performance, this paper conducts contrastive experiments for solid and perforated spiral fin heat exchangers (SSHX and PSHX) at five inclination angles (0°, 45°, 90°, 135°, 180°). Solid-liquid evolution and temperature history of the thermal charge/discharge process were recorded, heat transfer characteristics were compared, and energy storage efficiencies were analyzed. The results show that the inclination angle can significantly influence the phase change process of SSHX and PSHX, with the highest values of the indices for PSHX and SSHX at 0°, and the lowest values at 135° and 90°orientation. After the optimization of the inclination angle, the average heat transfer rate and heat flux can be increased by 15.5 % ∼ 84.4 % in thermal charge and 6.3 % ∼ 22.1 % in thermal discharge. Perforations enhance internal convective flows within the heat exchangers across all inclination angles, especially for the vertical orientation with a significant melting rate increase, but such heat transfer contributions are diminished as the angle towards the horizontal orientation. Top-side injection of heat transfer fluid yields better thermal performance than bottom-side injection. The highest energy storage efficiencies for PSHX and SSHX reach 63.4 % and 62.9 %, respectively. These results can provide valuable guidance for practical engineering applications.