Effect of fin number on the melting phase change in a horizontal finned shell-and-tube thermal energy storage unit

Thermal assessment on solid-liquid energy storage tube packed with non-uniform angled fins

Phase change materials (PCMs) have been proposed to manage the temperature of lithium-ion batteries in new energy vehicles, sharing the merits of low energy consumption, high temperature uniformity and affordable price. The low heat extraction rate as to low PCM thermal conductivity and the limited thermal storage capacity are the two major flaws of PCM-based battery thermal management systems. To fix these two flaws, three enhancement strategies (and corresponding specific measures) have been developed, which are increasing heat extraction rate (increasing PCM thermal conductivity and extending heat transfer area), recovering thermal storage capacity (coupling PCM with other cooling techniques) and reducing PCM cooling load (hybridizing PCM with other cooling techniques). In this review paper, the reinforcement principle of these measures was illustrated firstly. Following that, the advancement of each measure was reviewed comprehensively. With enhancement strategies, the thermal management performance has been improved considerably, demonstrating the feasibility and potential of PCM-based systems. No commercial vehicles, however, have adopted this type of system. Finally, a research roadmap from material level, to cell level and to system level was refined and eight research directions were proposed. In summary, a string of problems still need to be solved and efforts should be poured into sustainedly for the commercialization of PCM-based systems.

A review on thermal management performance enhancement of phase change materials for vehicle lithium-ion batteries

Adding longitudinal fins is an efficient method to enhance the melting behavior of a horizontal heat-storage tube. Nevertheless, the inhomogeneous heat transfer intensity, which is brought by the natural convection of liquid phase change material, causes a hard-melting region in the bottom half of the tube. In this study, two-dimensional models considering natural convection have been established to investigate the melting of phase change material in the latent heat storage unit with longitudinal fins. Optimization of the structural parameters, including fin-thickness and fin-length, are conducted and numerically calculated to accelerate the melting process. To enhance the charging of the hard-melting region, four strategies are employed and compared with the conventional model 1, whose fin length and fin thickness are constant. It is observed that the intensity of heat transfer is higher in the top-half domain, and it is lower in the bottom half. Moreover, thickening the bottom fins and thinning the top fins can efficiently enhance the charging process. An 8.7% reduction in the complete melting time can be realized by model 6 with the thickest bottom fins as compared to model 1 with equal length and equal thickness fins. Meanwhile, model 9, who has the longest bottom fins, can reduce the complete melting time by 47.1% as compared to model 1, so that the method of lengthening the bottom fins and shortening the top fins is likewise useful in accelerating the melting process. Based on the two strategies, we proposed an optimal model 10, who has the thickest and longest bottom fins, is conducted, and the complete melting time can be reduced by 54.1% compared with the original model 1. Consequently, the key limitation of heat storage in the horizontal tube is located in the bottom half, which is defined as hard-melting region, and thickening and lengthening the bottom fins is conducive to enhance the heat storage in the horizontal tube.

Influence of fin parameters on the melting behavior in a horizontal shell-and-tube latent heat storage unit with longitudinal fins

Effect of geometry modification on the thermal response of composite metal foam/phase change material for thermal energy storage

Melting performance enhancement of a latent heat storage unit using gradient fins

Heat transfer investigation of a flat-plate oscillating heat pipe with tandem dual channels under nonuniform heating

A theoretical model of unsteady melting heat transfer in a horizontal tube-shell TES unit is established and numerically solved based on the enthalpy-porosity method. In present research, the evolution of temperature field, velocity field, melting front and PCM enthalpy during the melting process under gravity and microgravity fields are compared and analyzed. The results indicate that the melting heat transfer under microgravity is dominated by heat conduction, while the natural convection dominates in the melting process under gravity. Consequently, melting performance under microgravity is weaker than that under gravity. Under gravity condition, vortices appear in the top half of the PCM and accelerate the melting process, and then the melting rate slows down gradually with the decrease of temperature gradient in PCM. However, due to no flow in the melting zone and the poor thermal conduction of PCM under microgravity, the melting area moves slowly outward in a circular type along the radial direction. In addition, the enthalpy difference of PCM under these two cases gradually enlarges as the melting goes on. At a typical time of 26,000 s, the enthalpy value of PCM under gravity is twice that under microgravity.

Numerical Study on Melting Phase Change under Microgravity

Thermal performance of a novel dual-serpentine-channel flat-plate oscillating heat pipe used for multiple heat sources and sinks

The invention discloses a horizontal tube-shell type energy storage heat exchanger. The horizontal tube-shell type energy storage heat exchanger comprises a round outer sleeve and a heat medium tube penetrating through the round outer sleeve, wherein an energy storage space is formed between the heat medium tube and the outer sleeve, the energy storage space phase is filled with a phase change energy storage material, the heat medium tube is internally used for allowing thermal fluids to be circulated, n ribs extending in the length direction of the heat medium tube are arranged in the circumferential direction of the heat medium tube, wherein n is larger than or equal to 4, and n is an even number; and two of the ribs are vertically distributed on the center line of the heat exchanger, the rest (n-2) ribs are symmetrically distributed on the two sides of the center line, the energy storage space on the two sides of the center line is divided into n/2 sector areas, the vertex angles Theta of the n/2 sector areas are changed from top to bottom according the rule that Theta n = Theta (n+1)-Phi, wherein Theta (n+1) represents the included angle between the ribs behind the included angle of Theta n, and Phi represents the difference value between the included angles of the ribs. According to the horizontal tube-shell type energy storage heat exchanger, heat of the thermal fluids ismore fully transferred to the whole heat exchange surface, so that the heat exchange property between the heat exchange fluids is enhanced, and the energy storage performance is improved.

Xi Chen

Papers

Melting performance enhancement of a latent heat storage unit using gradient fins

Heat transfer investigation of a flat-plate oscillating heat pipe with tandem dual channels under nonuniform heating

Numerical Study on Melting Phase Change under Microgravity

Thermal performance of a novel dual-serpentine-channel flat-plate oscillating heat pipe used for multiple heat sources and sinks

Horizontal tube-shell type energy storage heat exchanger