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With the rapid development of microelectronic devices, efficient thermal management in narrow spaces faces significant challenges. Two-phase heat transfer technology is proposed as a breakthrough in this field; however, big challenges, especially in designing a high-performance wick within limited space, are urgent to be addressed before ultrathin two-phase heat transfer devices (TPHTDs) can be further applied. In this study, a multilayer composite micromesh wick (MCMW), comprised of coarse and fine meshes with different layer combinations, is proposed to enhance the wicking capability, which is promising to further enhance the thermal performance of ultrathin TPHTDs. Capillary rise rate experiments are conducted to evaluate the comprehensive wicking capability. The results show that MCMW structures yield a significant wicking capability enhancement when compared with multilayer single mesh wick (MSMW) structures. The MCMW, consisted of 3 layers of 100-mesh and 3 layers of 300-mesh, exhibits an optimum volumetric flow rate of 14.44 mm3/s and an equilibrated wicking height at 55.98 mm. MCMW structure provides a convenient and effective alternative in enhancing the wicking capability of mesh wicks and the thermal performance of ultrathin TPHTDs.

Due to the demands of thermal performance enhancement of heat pipe solar collector, the fabrication of large-area flat heat pipes with the advantages of low cost and outstanding thermal performance has become more urgent. In this paper, a large-area ultra-thin flat heat pipe (LUFHP) with multiple parallel microchannels was fabricated by the aluminum extrusion process. Its total thickness is only 1.5 mm while the effective width is 170 mm. The effect of different filling ratios on the thermal performance was investigated under natural air convection and forced water cooling, respectively, including heat transport capability and thermal resistance. The experimental results indicate that the maximum heat transport capabilities for natural air convection and forced water cooling are 40 W with an optimal filling ratio of 25% and 25 W with an optimal filling ratio of 30%, respectively. The minimum total thermal resistances of the LUFHP are about 0.22 °C/W (natural air convection) and 0.73 °C/W (forced water cooling), which decrease by 74% and 57% compared with these of aluminum plate, respectively. That is, the proposed LUFHP shows better thermal performance under NAC for the replacement of aluminum plate in a wider range of heat load.

Micro-grooved aluminum flat plate heat pipes (MFPHPs), fabricated by hot extrusion and subsequent inner surface treatment via chemical corrosion, were developed to improve the thermal efficiency and reduce the costs of solar collectors. Thermal performances of MFPHPs, including temperature distribution, maximum heat transfer capability, and thermal resistance, were experimentally conducted. The effects of treatment time and solution concentration on the thermal performance enhancement of MFPHPs were also investigated. The experimental results show that inner surface treatment can substantially enhance the thermal performance of MFPHPs, and different treatment morphologies of inner surfaces result in differences in thermal performance enhancement. The optimal treatment parameters were determined to be a treatment time of 10 min with a solution concentration of 1.5 moL/l. This resulted in the optimal thermal performance enhancement: an increase of approximately 80% in heat transfer capability and a decrease of more than 44% in thermal resistance, compared to the untreated MFPHP. This study provides a convenient, effective, and low-cost method to enhance the thermal performance of MFPHPs applied in solar collectors.

This paper is aiming to improve the ultrasonic heat transfer enhancement by controlling the sound intensity distribution and constructing an acoustic focusing field, which can reduce energy dissipation and dramatically enhance the local sound intensity of heat transfer surface. Two design criteria are proposed to construct the acoustic focusing field by utilizing acoustic interference and acoustic resonance. Correspondingly, an elliptical acoustic focusing tank is designed and fabricated. Two-dimensional simulation and experimental tests of sound intensity distribution in the elliptical acoustic focusing tank are performed to verify the theoretical conception and design. In addition, the heat transfer coefficients are measured at different locations in the elliptical tank under natural convection, using a square tank as a control. The experimental results show that the elliptical acoustic focusing tank can promote the intensity of the whole sound field, especially the focus region compared with the square tank. The heat transfer coefficient and heat transfer enhancement rate anywhere in the elliptical tank is higher than that in the square tank. The maximum heat transfer enhancement rate of the elliptical tank is 55.3% in natural convection, which is 47.1% higher than that of the square tank under the same condition.

A novel ultra-thin aluminum flat plate heat pipe (UAFHP) with dimensions of 120 × 120 × 2 mm was developed for the thermal management of concentrated electronic equipment. An evaporator container with support posts and a filling hole was manufactured integrally by the stamping method. The surface-functional wicks, which were fabricated by a micro-milling method, consisted of array orthogonal microgrooves and the groove surfaces were covered with grain-like microstructures. The effects of heat load, cooling-water temperature, and tilt angle on the heat transfer characteristic of UAFHP, including its thermal response performance, temperature distribution and thermal resistance, were investigated experimentally. The results showed that UAFHP exhibits a favorable thermal response performance and heat transfer performance. It can effectively dissipate 160 W and has a minimum thermal resistance of 0.156 °C/W in the horizontal orientation. Moreover, when the cooling-water temperature decreases, the wall temperature of UAFHP decreases while the thermal resistance of UAFHP increases. In addition, small tilt angles (θ ≤ 30°) have a negligible effect on the heat transfer characteristic of UAFHP. Compared with the flat plate heat pipes reported in the literature, UAFHP could significantly meet the requirements of thermal management of concentrated ultra-slim portable electronic equipment because of its advantages such as light weight, favorable heat transfer characteristic, ease of fabrication and low cost.

A novel composite heat pipe (CHP) that consists of a conventional heat pipe (HP) with a phase change material (PCM) storage chamber wrapped on the adiabatic section was proposed in this work. The CHP combines the advantages of the high thermal conductivity of HP and the high thermal storage capacity of the PCM. A measurement system was established to analyze the thermal performance with different effect factors of the CHP, including the filling rate of the PCM, heating power and wind speed. Multi-cycle transient thermal controlling performance was also investigated. Results show that the CHP can enhance the absorption-dissipation thermal performance, improve the isothermality, decrease the start-up temperature and greatly reduce the thermal shock in cyclic thermal scenarios. We believe that the CHP can be developed as high-potential heat-transfer medium for reliable thermal management.

The thermal performance in various orientations of gravity was investigated for operating multi-branch heat pipes (MBHPs) with different sintered wicks in the case of cooling a heat source with dual condenser. The effect of sintered particle size in different orientations on heat transfer performance were investigated systematically. The particle size effect was examined with three copper powders of particle size of 50–75 μm, 75–100 μm and 100–125 μm in four orientations of gravity-assisted orientation, anti-gravity orientation, horizontal orientation, and compound orientation of gravity, respectively. All MBHPs were filled by deionized water to the filling ratio of 100%. Experiment results indicate that all MBHPs can operate with similar performance in all the tested orientations before dry-out occurring. Further, the MBHP with 75–100 μm copper powder performs best in all the tested orientations, considering both the thermal resistance and the heat transport capability. In addition, it can start up successfully within 10 min without temperature overshoot and oscillation. That is, a MBHP can perform well in all the tested orientations and the copper powder of 75–100 μm is a good candidate for better thermal performance.

We demonstrate an organic macromolecule-assisted anion-exchange reaction method for tuning the emission spectrum of cesium lead halide perovskite (CsPbX3) nanocrystals (NCs) from green to near-ultraviolet using a microreactor. Using poly(lactic acid) (PLA), the emission peak of CsPbX3 NCs can be tuned from 514 nm to 420 nm while maintaining high photoluminescence (PL) quantum yields (QYs) of 33–90%. By taking advantage of the microreactor, we synthesize parent CsPbBr3 NCs and complete anion-exchange reactions at the same time, which is more efficient than most previously reported methods. The stability of CsPbX3 NCs is improved by PLA coating, especially for CsPbCl3, which shows long-term stability under ambient conditions for at least two weeks. The CsPbBr3 NCs are utilized with a red phosphor on a blue light emitting-diode (LED) chip, achieving white light emission with a luminous efficacy of 62.93 lm W−1 under a 20 mA driving current. Highly efficient white LEDs (wLEDs) demonstrate the potential of halide perovskite NCs for optoelectronic applications, including low-cost displays, lighting, and optical communication.

Flexible woven heat sink (FWHS) is proposed to meet the heat-dissipation demand of a light emitting diode headlamp, which can be installed in limited spaces. The heat sink comprises three copper belts manufactured by weaving copper wires, with a structural advantage of high flexibility. The thermal-resistance network model of the headlamp with the FWHS was established. A test system was implemented to analyze the factors affecting the heat transfer, such as the expanded forms, input power, ambient temperature, and wind speed. The expanded form of the FWHS can be adjusted by changing the inclination angles α and β. α means the inclined angle between the adjacent woven belts, and β means the inclined angle of each woven belt expanded along the folding part. The optimal expanded form is the status with α = 25–90° and β = 25–40°. The overall temperature of the headlamp increases almost linearly with the increase in the input power and the ambient temperature. The cooling effect of the FWHS is enhanced with the increase in the wind speed; the optimal wind speed is approximately 2 m/s.

The grooved wick has a promising potential in the field of ultra-thin flat heat pipes, and the porous structure can improve the capillary performance of grooved wicks significantly. In this paper, an environmentally friendly method, named as ultrasonic modification, was developed to fabricate porous microstructures on grooved aluminum wick. The effects of ultrasonic modification times on the morphology, wettability and capillary performance of the porous grooved wick were investigated. The results indicate that appropriate ultrasonic modification times can realize an excellent distribution of porous microstructures throughout the groove surface. After ultrasonic modification, the modified surface became hydrophobic since the porous microstructures were covered with a low-surface-energy coating. However, in case of aluminum heat pipes with acetone as working liquid, the wettability and capillary performance of the modified grooved wick can still be enhanced significantly. The maximum capillary rise height and the capillary performance parameter of the modified grooved wicks were increased for a factor of 3 and an order of magnitude, respectively. This study provides a new idea for the fabrication of porous aluminum wicks, which is beneficial to promote the development of ultra-flat aluminum heat pipes.

In this study, a double-scale composite microgroove wick (DCMW) fabricated using crisscross plough-extrusion (CPE) method and subsequent chemical corrosion surface treatment is proposed for improving the heat transfer performance of copper‑aluminum composite vapor chambers (CACVCs). The wicking capability of a DCMW was characterized using a capillary rise experiment with ethanol as the working fluid. The wicking rise process was recorded using an infrared thermal imager, and the surface morphology and surface wettability of the DCMW were investigated. The effect of corrosion time on the wicking capability of the DCMW was also studied. The experimental results indicated that the equilibrium wicking height of the DCMW was significantly higher than that of an uncorroded microgroove wick. The optimal corrosion time was determined to be 15 min. DCMW with the optimal treatment exhibits a capillary performance parameter ( K R eff ) of 3.81 μm and volumetric flow rate of 3.64 mm3/s, an increase of 442% and 127.5% relative to that of an uncorroded microgroove wick, respectively. Furthermore, the results indicated that the combination of the CPE process and chemical corrosion provides a simple and effective method for improving the wicking capabilities of the wicks and the thermal performances of CACVCs.

Phase change heat transfer devices (PCHTDs) have been considered as an ideal choice for the application of high-power cooling. Wick, as the core of PCHTD, has received extensive attention. In this study, hierarchically 3D-textured copper surfaces (TSs) were fabricated as the potential wicks to meet the needs of high-power cooling in PCHTDs. Laser machining, as an efficient special processing means, was employed to complete the fabrication of TSs with different structural parameters. The capillary performance of the TSs, including capillary rise height and velocity, was evaluated by the infrared thermal imaging method with ethanol as working fluid. In particular, the maximum volumetric flow rate of the textured surfaces due to the capillary wicking was found to dominate the two-phase heat transfer capacity through saturated pool boiling tests. The best two-phase heat transfer performance was achieved by TS75 with the critical heat flux of 173.9 W/cm2 and the maximum heat transfer coefficient of 34.6 W/cm2K, which are 1.54 and 5.71 times higher than those of the plain surface. Comparative studies with other capillary structures indicated that TSs have comparable or even better enhanced heat transfer performance, making it a promising wick for the application of high-power cooling devices.