The demand for efficient dehumidification in evaporators has become one of the key technical challenges restricting the high-quality development of the refrigerated air dryer industry. To investigate the effects of fin structure on the air-side heat transfer and dehumidification performance of finned-tube evaporators applied in refrigerated air dryers under the operating conditions of 50 °C, RH = 85%, numerical heat and mass transfer models for the air side of evaporators with plain fins and wavy fins were established based on the Ansys Fluent software 2022R1. The study found that wavy fins possess superior heat transfer and moisture removal capabilities. Key performance indicators, including the air-side heat transfer rate (Q), moisture removal amount (Δm), friction factor (f), and the nusselt number (Nu), were all higher for wavy fins compared to plain fins. Building upon this, three types of vortex generators (VGs) were introduced to further optimize the performance of the wavy fins, aiming to balance heat transfer enhancement and flow resistance control. At an attack angle of 30°, the comprehensive performance factor (JF) showed the highest improvement, reaching 43% with the Delta Winglet vortex generators. The 15° configuration also showed improvement, while 45° led to the worst performance due to increased flow resistance. The results indicate that for typical high-temperature and high-humidity environments, the wavy fin is recommended as the preferred choice due to its superior overall performance and simple structure. For applications requiring higher dehumidification capacity, wavy fins equipped with vortex generators can be selected to achieve the most efficient dehumidification. This study provides valuable insights for the design and application of finned-tube evaporators in dehumidification systems under high-temperature, high-humidity conditions for refrigerated air dryers.

To improve the thermal management performance of lithium-ion batteries under high discharge rates and complex operating conditions, a bidirectional parallel bionic flow-channel cooling plate is proposed, with agricultural electric forklifts taken as the representative application background. Numerical simulations were first carried out to compare the heat dissipation characteristics of a conventional leaf-vein flow channel, a unidirectional parallel bionic leaf-vein flow channel, and a bidirectional parallel bionic leaf-vein flow channel. On this basis, the effects of structural parameters on the thermal performance of the liquid cooling plate were systematically investigated using a single-factor analysis method. Furthermore, an orthogonal optimization experiment was performed for four major influencing factors. The results indicate that the unidirectional parallel bionic leaf-vein flow channel improved the coolant coverage relative to the conventional leaf-vein structure; however, owing to the one-sided coolant supply mode, a high-temperature retention zone tended to appear at the end of the channel. In contrast, the bidirectional parallel bionic design effectively alleviated this problem by supplying coolant synchronously from both sides. The main channel width, branch channel width, total channel height, and branch inclination angle were identified as the dominant factors affecting heat dissipation performance. Under the optimized structure and operating condition, the maximum temperature and temperature difference of the battery module were reduced to 29.85 °C and 4.48 °C, respectively.

Most existing stick-slip piezoelectric actuators cannot actively suppress backward motion during operation, which degrades output performance and positioning accuracy. This study proposes a bidirectional stick-slip piezoelectric actuator inspired by the gait of starfish tube feet. The actuator combines a symmetric flexure-hinge structure with four PZT stacks and a tube-foot attach-pull-switch (TF-APS) control sequence. During each sequence, the driving side first establishes effective contact with the slider through its normal PZT stack and then advances the slider tangentially. The opposite side subsequently locks the slider and takes over load support before the driving side disengages and resets. This sequence maintains effective contact on at least one side, thereby reducing return-stage backward motion and enabling stable bidirectional stepping. An equivalent mechanical model of the flexure-hinge mechanism was established, and a direct FEM parameter scan was used to evaluate key geometric parameters and determine the structural dimensions. A prototype was then fabricated and tested to characterize its output, bidirectional motion, and return-stage backward-motion suppression. Its performance was also compared with that under a conventional stick-slip sequence. The actuator achieved a maximum speed of 4.31 mm s ⁻¹ . The TF-APS sequence markedly reduced return-stage backward displacement and enabled stable bidirectional motion. At 150 V and 100 Hz, the actuator maintained stable motion at approximately 1.7 mm s ⁻¹ under a carrying load of 10 N.