Liquid Microchannel Research Articles

Research Progress of Microchannel Liquid Cooling Technology in the Application of Thermal Management of Prismatic Lithium Batteries (Withdrawn)

Lithium-ion batteries have significant advantages such as high energy density, long cycle life and low self-discharge rate. Therefore, they are ideal for energy storage in electric vehicles. However, lithium-ion batteries are very sensitive to temperature, which affects the battery's cycle life, efficiency, reliability and safety. During the charging and discharging process, a large amount of heat is generated inside the battery due to the electrochemical reaction and resistance, causing the battery temperature to rise. When the temperature gets too high, thermal runaway, electrolyte fire and explosions may occur. As battery energy density increases, the demand for efficient thermal management continues to increase, and a compact and efficient battery thermal management system is essential. This paper introduces the development status of different thermal management technologies, reviews the application of microchannel liquid-cooling technology in the thermal management of prismatic lithium batteries, discusses the current research direction and status of microchannel technology, and finally looks forward to the future research and development direction of microchannel technology.

A numerical study on a hybrid battery thermal management system based on PCM and wavy microchannel liquid cooling

With the emerging development of electrical vehicle, the efficient thermal management of the lithium-ion battery is becoming a critical point for its wide application and normal operating. Hence, based on the advantages of liquid cooling and PCM, a novel hybrid cooling system using PCM coupled with wavy microchannel cooling plate (PCM-WMCP) was proposed in this paper, and a numerical study was carried out to investigate its performance. It's found the hybrid cooling system with PCM and microchannel cooling plate showed much lower battery temperature than individual PCM and air cooling systems, moreover, among the hybrid cooling systems, the novel PCM-WMCP exhibited 2 K lower maximum battery temperature than PCM-SMCP (straight microchannel cooling plate) type at 1C, and increased potential in utilizing PCM for heat dissipation. The PCM was further modified to composite PCM (CPCM) by adding expanded graphite, which was found to realize a further lower maximum battery temperature and more uniform battery temperature field, with graphite mass fraction of 10 %. Besides, facing thermal runaway, the CPCM-WMCP cooling system showed a better temperature control ability compared to CPCM-SMCP, with temperature suppressed to below 318 K, and the maximum temperature difference at about 1.6 K.

A Sensitive Fluorescence Analysis Method of Pathogenic Microorganisms Based on Silicon Photomultiplier.

The monitoring of pathogenic microorganisms in water is important for public health and disease outbreaks prediction. Recently, optical detection techniques have drawn much attention due to the advantages of rapid response, security and high sensitivity. In this paper, a fluorescence spectrometer based on 375nm exciting laser and the microchannel liquid sample flow technology is proposed. The 4 × 4 narrowband filter array was coupled to a Silicon Photomultiplier (SiPM) array with single-photon sensitivity. B500 fluorescent microspheres and Escherichia coli were used for performance evaluation of the spectrometer. As a result, it is feasible to use random particle counting method to detect the bacteria concentration level in water even low to several CFU/mL. In addition, based on Python tools and neural network algorithm models, the fluorescence spectra of different kinds of substances (biotic and abiotic) can be classified with an accuracy of more than 97%. The method was successfully applied to tap water samples. The results suggest that the proposed method is applicable for on-site bacteria detection.

Balance regulation of heat transfer and flow performance in convective heat exchange process of microchannel plates

As high-performance computing devices continue to evolve toward miniaturization and integration, chip performance has increased significantly. However, chip dimensions are simultaneously shrinking. This trend has led to more challenging high heat flux density issues. Microchannel liquid cooling is an effective way to solve this issue, where the most critical aspect is the balance regulation of heat transfer performance and fluid dynamics. To address this challenge, this study initially divided a complete microchannel plate into two parts: an inlet distribution chamber (IDC) and an array structure. Subsequently, anentransy dissipation rate modeland apumping power consumption modelwere established for themicrochannel inlet diversion chamber, and an optimization design was carried out. This solved the problems of the optimal branch level and optimal channel size for designing the microchannel IDC within a given space. Next, themicrochannel array structurewas optimized to minimize boththermal resistanceandoverall flow resistance. This approach facilitated proactive optimization design for the microchannel array structure within the specified space. Finally, the independently optimizedinlet diversion chamberandarray structurewere combined into a complete optimized microchannel plate. Several comparative structures were also designed under the same constraints. Experimental research was conducted to validate the reasonableness of the optimization. The results indicated that, compared to randomly designed structures, the average overall performance of the optimized structure within the study scope hadincreased by at least 1.16 times, with the highest improvement reaching4.29 times. This study provides a theoretical reference for the active optimization design of microchannel plates in convective heat exchange process.

Soft Monolithic Shielded Sensors to Measure Shear and Normal Forces for Local Slip Detection

AbstractSoft force sensors enable closed loop control or autonomous operation of compliant robot systems. A stretchable force sensing surface containing an array of independent sensor units is reported. This design allows for the measurement of local shear and normal forces at multiple locations, independently, providing real‐time, multi‐axis force information at each unit. The sensor array is based on capacitive strain sensing, using liquid metal electrodes and air microchannel for high sensitivity. Electromechanical interference between adjacent sensor units is addressed and eliminated through design optimization and the use of compliant electrical shield layers. A 1D sensor array is applied to gripping tasks, where the independent sensor readings enable detecting local and partial slipping. This study illustrates how the device can be used to explore the dynamics of local forces during the stages of pick up, slip, and release.

Design and Numerical Study of Microchannel Liquid Cooling Structures for Lithium Batteries

To investigate the microchannel liquid cooling system of 18650 cylindrical lithium battery packs, cooling systems with varying numbers of microchannels are developed and they are analyzed through numerical simulations using COMSOL software. The findings reveal that lower coolant inlet temperatures correspond to lower maximum temperatures during discharge, with temperatures decreasing closer to the inlet. When the coolant passes through a 3.6 mm diameter or at an inlet flow rate of 0.1 m s−1, an increase in Reynolds number results in a decrease in the highest temperature of the cells. However, this temperature reduction slows down when Re exceeds 400. The annular channel cooling structure demonstrates superior cooling effects and temperature uniformity. Optimization opportunities exist to reduce the number of inlets. The dual‐inlet and dual‐outlet cooling structure has been enhanced by adjusting the number of channels in the annular channel design. This modification has resulted in a maximum temperature reduction of 4.62 K and a temperature difference of less than 5 K compared to the initial reference group, demonstrating effective cooling performance.

Hybrid cooling system with phase change material and liquid microchannels to prevent thermal runaway propagation within lithium-ion battery packs

Thermal runaway propagation in battery pack can cause catastrophic hazards without timely countermeasures. This paper presents the establishment of lumped thermal resistance model for battery pack and introduces an innovative hybrid thermal management system designed to suppress thermal runaway propagation. First, a heat generation model describing the reaction dynamics of cell thermal runaway is developed and validated by experiment. Subsequently, a lumped thermal resistance network is formulated for the large-scale battery pack using electrical circuit elements and simulation studies for the thermal runaway propagation are carried out. The results reveal that the thermal runaway propagation progress triggered by four cells can accelerate by nearly 40 % compared to that initiated by a single cell. Consequently, a hybrid thermal management incorporating phase change material and liquid microchannels is designed. Comparative analysis with individual cooling systems demonstrates the superior effectiveness of the proposed system in suppressing the first round of thermal runaway propagation. The temperatures of neighbor cells only have a marginal climb to about 80 ℃ in the initial 600 s, which is well below the thermal runaway triggering temperature. This work can provide valuable insights into the structural design of thermal management systems for battery packs in practical applications.

Liquid metal manifold microchannel heat sink for ultra-high heat flux cooling

Advanced heat dissipation technology is crucial for chip operation and performance utilization. Room temperature liquid metal convection cooling technology has demonstrated its efficacy as a viable approach for addressing high heat flux heat dissipation. However, the smaller specific heat capacity of liquid metal leads to a large temperature rise, hindering the advancement of its cooling technology. To address this, a liquid metal manifold channel structure is proposed to convert the continuous long-range flow into a segmented short-range flow. The good matching between liquid metal and manifold structures is adequately demonstrated through a comparison with alternative coolant and channel structure. The simulation results demonstrate the effectiveness of liquid metal manifold channel cooling in dealing with a heat flux of 1000 W/cm2, ensuring that the maximum temperature of the chip remains below 351.7 K. Moreover, the convective heat transfer coefficient even reaches 106 W/(m2·K), which is ten times larger than that of water conventional microchannel heat sink. Orthogonal experiments analyzed the impact of structural parameters on dissipation performance, including the height of the microchannel, ratio of manifold length to fin length, length of fin in manifold, width of channel, and ratio of fin with to channel width. The height of the microchannel has been identified as the most critical factor. This manifold structure mitigates the inherent limitation of liquid metal's lower specific heat capacity, enabling efficient thermal management for electronic devices under ultra-high heat flux conditions.

Experimental and numerical analysis of variable cross-section channel liquid cooling plate for server chips thermal management

Utilizing high-performance chips results in increased heat generation, necessitating more effective heat dissipation method. To address challenges in microchannel liquid cooling plates for server chips cooling the study presents the variable cross-section channel liquid cooling plate designs. To investigate the effect of channel structure on the performance of liquid cooling plate, two types of samples, one featuring side wall ribs and bottom cavities (SC) and the other featuring side wall ribs and bottom waves (SW), are evaluated through experimental analyses under various heating power and flow rate conditions. Comparing their performance to a conventional rectangular channel (RC) liquid cooling plate, their heat transfer and flow attributes were assessed. Finally numerical analysis was conducted to investigate the flow behavior inside the channel and extreme performance prediction were made using the numerical study. Results demonstrate that the SC and SW designs outperform the RC in terms of heat transfer capabilities, despite having the weaker flow characteristics. Under 300 W heat source power, the SW variants enable the heat source surface temperature to stay below 77.8 °C with a 194 mL/min flow rate. Notably, the SW variant showcases lower average heat source surface temperature and demonstrates lower pressure drop compared to the SC variant. As the flow rate increases, the heat transfer efficiency of the SW variant is further amplified while simultaneously highlighting the relatively suboptimal flow behavior of the SC variant. Predictive numerical models underscore that the SW variants offers improved thermal performance when subjected to high heat source power scenarios. Remarkably, under the heat source power of 500 W, a mere augmentation in flow rate proves sufficient to reduce the heat source temperature below the prescribed threshold value. The combination design of side wall ribs and bottom waves should enable a low cost, simple and high efficiency electronics cooling.

Switchable and optically transparent ultrawide stopband frequency selective surface for electromagnetic shielding

In view of the fact that high-frequency electromagnetic waves mainly enter buildings through windows and glass doors, switchable optically-transparent shielding with broad stopband is increasingly needed. Herein, a novel design for a switchable and optically transparent frequency selective surface (FSS) with ultrawide-stopband is presented in this study. The structure consists of a polymethyl methacrylate (PMMA) layer sandwiched between polydimethylsiloxane (PDMS) layers which contain liquid metal microchannels arranged in an orthogonal Ω-shaped configuration. The mobility of the liquid metal can switch the FSS response from an all-pass to an ultrawide bandstop behavior. The proposed FSS achieves a rejection bandwidth of 18.1 GHz, covering P, L, S, C, X and Ku bands, while maintaining a transparency of 81% and high angular stability up to 80°, regardless of polarization. Furthermore, the mechanism behind the ultrawide stopband and high angular stability is explored through an analysis of reflection and absorption for both TE polarization and TM polarization. Experimental validation under both normal and oblique incidence demonstrates the ultrawide-stopband performance of the fabricated FSS.

Temperature fields analysis and heat dissipation structure design of an film capacitor in new energy vehicle

The high-temperature resistance performance of film capacitors in motor controllers faces greater challenges with the development of high voltage and high power density of new energy vehicles (NEVs). In this study, a typical film capacitor is taken as the object of research; simulations of temperature fields and experiments on temperature rises are conducted. Additionally, a heat dissipation structure is designed to enhance the high-temperature resistance performance of the capacitor. Firstly, the temperature field distributions of the capacitor under different ripple currents and ambient temperatures are analyzed using ANSYS electro-thermal coupling simulation. Then, under the same operating conditions, experiments on the temperature rises are conducted on the capacitor, which is installed with K-type thermocouples to verify the accuracy of the electro-thermal coupling simulation. Furthermore, an external heat dissipation structure consisting of a micro-channel liquid cold plate is designed for the capacitor, and the effectiveness of the external cold plate is verified through electro-thermal coupling and FLUENT simulations. It is found that under the operating conditions of 85 ?C ambient temperature and 175 A ripple current, the maximum temperature of the capacitor with the external cold plates decreases by 46.08% compared to the original capacitor. The results indicate that the external cold plates effectively improve the high-temperature resistance capability of the film capacitors in electric vehicles.

Thermal performance of a hybrid cooling plate integrated with microchannels and PCM

The battery thermal management system (BTMS) is critical to electric vehicle (EV) safety and performance. In this paper, a novel cooling plate integrated with liquid microchannels and phase change material (PCM) is developed for use in BTMS, and its thermal performance at a high discharge rate of 5C is investigated. To improve temperature inhomogeneity, the non-metallic inlet shell is used to transport the coolant to the axial microchannels, which significantly reduces the temperature difference by 3.8 °C. Additionally, compared with I-shaped microchannels, the design of S-shaped microchannels increases the flow area for coolant and promotes the cooling effect, controlling the maximum temperature at 34.53 °C. Then, the parameters, including the number of microchannel layers, radial extension angle, inner diameter, and PCM thickness, are optimized by the multi-objective optimization, and its energy consumption is decreased to 9.61 × 10-6Wh and its energy density raised to 108.94 Wh∙kg−1. Moreover, the cooling performance improves with the increase of the inlet velocity, and a balance between cooling performance and energy consumption is achieved when the inlet velocity is 0.06 m∙s−1. Cross-convectional flow helps to enhance the temperature uniformity of the battery module further. The hybrid liquid cooling plate takes advantage of coupling active cooling and passive cooling; the energy consumption of BTMS is reduced by 46.3% without sacrificing the cooling capacity when delaying the beginning of active cooling after PCM passive cooling for 300 s. Furthermore, the PCM-embedded hybrid cooling plate slows the heat loss of batteries in cold environments, which can maintain their temperature above 20 °C after resting for 2 h at 0 °C. This work provides a reference for the hybrid cooling plate development of cylindrical batteries.

Investigation of mass transfer in valve-controlled gas–liquid segmented flow

Segment flow is widely employed in gas–liquid microreactor systems owing to its enhanced mass transfer through the biphasic interface. Previous studies evaluating an increased fluid flow rate (F) have reported an increased volumetric mass transfer coefficient (kLa) and reduced segment length (L). In a conventional microsystem, manipulating L without varying the residence time of the fluids is challenging. Hence, the relationship between kLa and L has not been systemically investigated under the same F. In this study, L control without changing F is implemented by introducing a high-speed valve into a gas–liquid microchannel system, and the influence of L on kLa is investigated by altering the valve frequency (f). The results indicate that kLa in the segmented flow is negatively correlated with L at constant F and reaches 0.149 s–1 (332.6 times larger than that in the bubble), whereas the specific area (a) of the segmented flow increases with increasing f before the liquid phase is saturated. Moreover, a and instinct kLa can be predicted using f, F, and the microchannel diameter. The outcomes of this research will improve the understanding of the mass transfer phenomenon in gas–liquid segmented flows and provide support for the design of microreactor systems.

A Wireless and Wearable Body-Pressure-Monitoring System for the Prevention of Pressure-Induced Skin Injuries.

This article presents a wireless and wearable body-pressure-monitoring system for the on-site, real-time prevention of pressure injuries for immobilized patients. For the prevention of pressure-induced skin injuries, a wearable pressure sensor system is designed to monitor the pressure at multiple sites on the skin and to alert the danger of prolonged application of pressure on the skin with a pressure-time integral (PTI) algorithm. The wearable sensor unit is developed using a pressure sensor based on a liquid metal microchannel and integrated with a flexible printed circuit board that includes a thermistor-type temperature sensor. The wearable sensor unit array is connected to the readout system board for the transmission of measured signals to a mobile device or PC via Bluetooth communication. We evaluate the pressure-sensing performances of the sensor unit and the feasibility of the wireless and wearable body-pressure-monitoring system through an indoor test and a preliminary clinical test at the hospital. It is shown that the presented pressure sensor has high-quality performance with excellent sensitivity to detect both high and low pressure. The proposed system measures the pressure at bony sites on the skin for about six hours continuously without any disconnection or failure, and the PTI-based alarming system operates successfully in the clinical setup. The system measures the pressure applied to the patient and provides meaningful information from the measured data for early diagnosis and prevention of bedsores to doctors, nurses, and healthcare workers.

A Flexible Multifunctional Sensor Based on Triboelectric Nanogenerator for Measuring Variable Stiffness of Soft Grippers and Recognizing Item Size

AbstractThe monitoring of the grasping behavior of variable stiffness grippers has emerged as a challenge due to the increasing use of soft grippers in logistics sorting applications. In this research, a flexible multifunctional sensor is developed by combining a liquid metal microchannel structure with a granular single electrode which detects the bending angle and stiffness of the flexible gripper in real‐time. The novel works by integrating triboelectric nanogenerator with particle interference variable stiffness and detects the stiffness of the soft finger. It is found that increasing the loading force on the gripper by a factor of 2.39 does not affect the kinematic characteristics. The size of the grasped object is determined with 96% accuracy by detecting the resistance offered to the stretched liquid metal during the bending of the soft finger. A soft grasping system is built with multifunctional flexible sensors and the real‐time signal feedback during the grasp‐move‐release process of objects of different diameters and weights is demonstrated. Besides providing a theoretical and experimental foundation of variable stiffness and nondestructive grasping of the soft gripper, the anthropomorphism of the soft grasping gripper is implemented by employing a novel sensor.

Flexible microfluidic triboelectric sensor for gesture recognition and information encoding

Flexible triboelectric sensor has a broad application prospects in self-powered human-machine interface. However, due to the complexity of real environment, the output signal is easily disturbed, thus resulting in low reliability. Here, a flexible microfluidic triboelectric sensor (FMTS) was proposed by counting the number of wave peaks in output waveform. With a high transmittance of 82%, the FMTS shows bendable, twistable and conformable characteristics so that can be operated attached to skin. Based on triboelectrification and electrostatic induction between liquid stream, microchannel and interdigital electrodes, it enables to generate quantifiable voltage wave peaks. The FMTS has a maximum sensitivity of 0.418 kPa−1 and a wide detection range from 2.38 to 58.12 kPa with the microchannel width of 500 µm. For demonstration, a FMTS is attached to the finger, and the number of peaks is used to determine the angle of finger bending with a resolution of 10°. The machine learning approach is employed to achieve accurate recognition of five gestures with an accuracy of 99.2%. The information can also be defined by using waveforms generated by different combinations of movements. An encoding system that recognizes eight types of information with an accuracy of up to 98.8% is finally demonstrated.

N‐shape pressure drop curve of gas–liquid microchannel reactor and modeling

AbstractAccurate prediction of gas–liquid pressure drop is essential to microreactors design; however, the understanding of general rules of pressure drop in a wide gas–liquid flow ratio, especially smaller than 1.0, remains insufficient, Accordingly, this work systematically studies the pressure drop rule within the gas–liquid flow ratio of 0.2–2.0. The results show that, under a given gas velocity, the pressure drop first increases and then decreases, and finally back increases with the liquid flow velocity, and the named N‐shape pressure drop curve could be clearly observed. Besides, the rules of gas–liquid unit length and gas‐phase holdup are explored to reveal the mechanism behind the N‐shape pressure drop curve. Finally, three semi‐empirical correlations based on the gas–liquid unit length and separated flow model are successfully proposed for the N‐shape pressure drop. This work provides some important fundamental information for the reliable design of gas–liquid microreactors.

Numerical and experimental investigation of a novel liquid upper-feeding micro-channel flat loop thermosyphon cooling and heat recovery system

ABSTRACT A novel liquid upper-feeding micro-channel flat loop thermosyphon (LUF-MCFLTS) system was developed, to eliminate the drying phenomenon of the upper surface in the traditional LTS and provide a highly efficient solution for DC cooling and heat recovery. The effects of cooling capacity (cooling water flow rate and temperature), heat load, and filling ratio on the heat transfer performance of the LUF-MCFLTS system are investigated experimentally. The results indicated that with the increase in cooling water flow, the decrease in cooling water temperature, and the increase in heat load, the heat transfer performance of the LUF-MCFLTS system was better. Under a heat load of 500 W, a cooling water flow rate of 600 L/h, and a cooling water temperature of 15°C, the heat recovery efficiency could reach 86.28%. Compared with the MCFTS and MCFLTS systems in literature, the recovery efficiency of the LUF-MCFLTS system could be increased by 31.6% and 2.64%, respectively. In addition, an effective numerical model to predict the heat recovery efficiency of the LUF-MCFLTS system with the experimental data in the 2.07% error band has been established. This work provides a new idea and theoretical basis for the design of DC cooling and heat recovery system.

Study on the ozonation degradation of methylene blue enhanced by microchannel and ultrasound.

Azo dye-containing wastewater poses serious risks of environmental pollution because it is generally biologically toxic and resistant to conventional wastewater treatment methods. A novel degradation system integrating ozone, microchannel, and ultrasound was designed to effectively degrade azo dye-contaminated wastewater. The effects of discharge voltage of dielectric barrier discharge (DBD) reactor, liquid flow rate, microchannel width, ultrasonic power, initial pH, and reaction temperature on methylene blue (MB) decolorization were studied. A maximum MB decolorization efficiency of 92.7% was obtained in the ozone/microchannel/ultrasound (O3/MC/US) system with 14 min of treatment. In addition, the 14-min decolorization efficiency and TOC removal efficiency obtained in O3/MC/US system were increased by 12.6 and 6.5%, respectively, compared to those obtained in the pure O3 system. Based on the results of scavenging experiments, the combined effects of microchannel and ultrasound were proved to improve the contribution rate of hydroxyl radicals, thus improving the decolorization efficiency. The present work clearly illustrates that ozonation degradation can be effectively enhanced by microchannel and ultrasound, and also provides a feasible method for the treatment of organic wastewater.

A parametric study of a hybrid battery thermal management system that couples PCM with wavy microchannel cold plate

In the actual use of electric vehicles, the battery will face complex and changeable working conditions, and the battery thermal management system (BTMS) is of vital important. In this paper, an innovative system using PCM and wavy microchannel cold plate (WMCP) called hybrid wavy microchannel cold plate (HWMCP) is designed and its parameters are analyzed and optimized. The results indicate that the heat storage capacity of HWMCP increases with the increase of PCM thickness and height ratio h1/h2. The cooling capacity of HWMCP is slightly improved when the liquid microchannels grow in number. Compared with unidirectional flow, cross flow significantly reduces the maximum temperature of the battery and improves the utilization rate of PCM. For HWMCP, the mass flow rate should be matched with the phase transition temperature to avoid premature complete melting of the PCM. Besides, lower phase transition temperature could play the role of absorbing heat earlier, and the temperature of the battery pack also decreases more obviously. After parameter optimization, the maximum temperature of HWMCP is 2.3 k lower than that of WMCP at 400 s under pulsed heat load and the temperature difference is reduced by 0.5 K. Moreover, in cold weather, the HWMCP extends the time required for the battery pack to drop to the lowest appropriate operating temperature. The results of this study provide a reference for the design of HWMCP.