Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

Abstract

Heat exchangers are general equipment for energy exchange in the industrial field. Enhancing the heat transfer of a heat exchanger with low pump energy consumption is beneficial to the maximum utilization of energy. The optimization design for enhanced heat transfer structure is an effective method to improve the heat transfer coefficient. Present research shows that the biomimetic structures applied in different equipment could enhance heat transfer and reduce flow resistance significantly. Firstly, six biomimetic structures including the fractal-tree-like structure, conical column structure, hybrid wetting structure, scale structure, concave-convex structure and superhydrophobic micro-nano structure were summarized in this paper. The biomimetic structure characteristics and heat transfer enhancement and drag reduction mechanisms were analyzed. Secondly, four processing methods including photolithography, nanoimprinting, femtosecond laser processing and 3D printing were introduced as the reference of biomimetic structure machining. Finally, according to the systemic summary of the research review, the prospect of biomimetic heat transfer structure optimization was proposed.

Influence of Groove Structure Parameters Based on Optimal Mass Transfer Coefficient on Vaporization Characteristics and Sealing Performance of Liquid Film Mechanical Seals

“…This indicates that the calculated value of the average vapor phase volume fraction increases with the mass transfer coefficient. Furthermore, the larger the mass transfer coefficient, the more similar the obtained value to the actual results, which is consistent with the conclusion obtained in [29]. After the mass transfer coefficient was set to 48, the average vapor phase volume fraction calculated each time had a growth rate of less than 1% compared with the previous calculation result.…”

“…However, in related studies, the mass transfer equation in the Lee model has a mass transfer coefficient whose value is usually based on the researcher's experience. This value lacks a theoretical basis, and the values in different documents are inconsistent [27][28][29]. The mass transfer coefficient is generally taken as a default value when studying the phase transition of a non-contact mechanical seal liquid film.…”

Study on the Drag Reduction Characteristics of the Surface Morphology of Paramisgurnus dabryanus Loach

“…The vortex behind the scale makes the high-speed fluid move away from the near-wall region, which effectively reduces the near-wall velocity and greatly weakens the turbulence. In addition, these vortices are located in low-pressure regions that continuously attract fluid, converting solid-liquid friction into liquid-liquid friction and effectively reducing drag [37]. The part marked with yellow in Figure 24c is the schematic diagram of the contact surface between liquid and a solid.…”

A Porous Media Leakage Model of Contact Mechanical Seals Considering Surface Wettability

“…[1], Green I. [2], and Lu [3] note that contact mechanical seals are a critical rotating equipment part as they reduce leakage, save energy, and protect the environment. Thus, they remain in the focus and research hotspot of both the scholars and engineers around the world [1][2][3], and Fan et al [4] thinks that the leakage failure of contact mechanical seals is still common.…”

“…[2], and Lu [3] note that contact mechanical seals are a critical rotating equipment part as they reduce leakage, save energy, and protect the environment. Thus, they remain in the focus and research hotspot of both the scholars and engineers around the world [1][2][3], and Fan et al [4] thinks that the leakage failure of contact mechanical seals is still common. Gu [5] noted that to effectively control and reduce the leakage of contact mechanical seals, it is necessary to focus on the main leakage channel formed between the end faces of the dynamic and static rings.…”