Effffect of inclination on the thermal response of composite phase change materials for thermal energy storage

Using paraffiffiffin as phase change material, the melting behaviors of pure phase change material and phase change material embedded in open-cell metal foams (composite phase change material) at difffferent inclination angles are studied. Experimental system enabling continuous rotating is designed and built to explore the inflfluence of inclination angles on phase interface evolution and temperature responses inside pure and composite phase change materials. Constant wall temperature is applied on one surface while others are thermally insulated. Experiments are carried out at angles of 0°, 30°, 60°, and 90° respectively. The effffects of inclination on the melting behavior of phase change materials are analyzed by visualizing the solid-liquid interface and analyzing the temperature responses. Results demonstrate that the inclination angle has a great inflfluence on the formation and development of natural convection during melting of pure phase change material, affffecting the solid-liquid interface propagation and heat transfer rate. Compared with the case at 90°, the full melting time is reduced by 12.28%, 22.81% and 34.21% at 0°, 30° and 60°, respectively. However, when phase change material is melted in open-cell metal foam, heat conduction dominates, and inclination angle has little inflfluence. Melting fractions at difffferent inclination angles are the same and temperature curves at given points overlaps with each other.

Thermal performance of a shell-and-tube latent heat thermal energy storage unit: Role of annular fifins

This study conducts numerical investigations on melting process in a shell-and-tube latent heat thermal energy storage (LHTES) unit with annular fifins. Commercial grade paraffifin is employed as the phase change material (PCM) and water serves as the heat transfer flfluid (HTF). Finite-volume-method (FVM) based numerical simulations are performed to investigate the effects of fifin number, height and thickness on the phase change process. Particular attention is made to justify the contribution of local natural convection to the overall phase change process. Results demonstrate that the full melting time could be maximally reduced by 65% by inserting annular fifins into PCM. For maximizing thermal performance, an optimal group fifin parameter (fifin number N = 31, thickness t/l = 0.0248 and interval l/L = 0.0313) is recommended for the present study.

泡沫金属／翅片填充管蓄热性能的实验研究

为了研究蓄热装置内填充复合相变材料后的蓄热性能，设计了一种填充通孔泡沫金属和环形 翅片的圆柱形蓄热罐，搭建了固液相变储热实验系统，并基于此系统对其熔化过程进行了实验研究， 记录了相变材料内的实时温度响应数据。研究结果表明：与泡沫金属管相比，泡沫金属／翅片管加速 了石蜡的熔化过程，缩短了整体相变时间；在实验工况下，完全熔化时间减少１６．７％；然而，翅片的加 入虽加速了顶部石蜡的熔化，但会抑制底部石蜡的熔化，使得石蜡内部不同高度间的温差扩大，温 度均匀性降低；此外，通过提高流量可以显著增强装置的蓄热响应速度，从而提高最终稳定温度。