Thermal Management Research Articles

Improvement of an ionic wind blower’s flow characteristic by auxiliary electrodes for thermal management of light-emitting diodes

Electronic device advancements in power, size reduction, and integration have resulted in increased heat flux and operating temperatures, negatively impacting the reliability of electronics. Ionic wind cooling is a new, environmentally friendly, and energy-efficient thermal management approach that effectively cools high heat flux local heat sources. However, enhancing ionic wind strength continuously can be challenging. In this study, an ionic wind blower consisting of an emitting electrode, a collecting electrode, and auxiliary electrodes is constructed. The experimental verification confirms the supplemental acceleration capacity of the auxiliary electrodes. When determining the optimal operating voltage applied to the auxiliary electrodes, the power consumption of the system and the intensity of the output ionic wind are taken into consideration. Theblower’s operational and structural factors, such as the emitter structure, discharge gap, and distance between the auxiliary electrodes and collectors, are optimized according to how they affect the device’s functional qualities. The improved blower’s heat dissipation ability is evaluated by cooling an LED chip. The results demonstrate that the system performs optimally with an emitter having seven needles, a discharge gap of 5 mm, and 9 mm between the auxiliary electrodes and the collector. The wind speed reaches 2.47 m/s, while the power consumption is only 1.6 W. Compared to the absence of auxiliary electrodes (47.7 W/(m2∙K)), the system’s mean convective heat transfer coefficient can reach 61.12 W/(m2∙K), resulting in a temperature reduction of the LED chip by up to 41.6 °C. With increasing voltage, the heat transfer enhancement ratio improves, enabling a blower with auxiliary electrodes to provide significant cooling while consuming less power.

Thermal management enhancement of photovoltaic panels using phase change material heat sinks with various T-shaped fins

A numerical simulation of the heat dissipation performance in photovoltaic (PV) cells with phase change material (PCM) for cooling is performed by COMSOL Multiphysics. A comparative analysis of two T-shaped fin designs in PCM heat sinks is conducted to evaluate their impact on the cooling performance of PV panels. The findings indicate that a 180° T-shaped fin design substantially outperforms a cavity without fin design, reducing the PV cell average temperature by up to 15.1 K and enhancing electrical efficiency by 1.36 %. Further optimization of distal fin distance and secondary length reveals that temperature uniformity and photovoltaic efficiency can be improved, achieving a maximum electrical efficiency increase of 1.40 % and a temperature uniformity enhancement of 71.0 %. Detailed analysis underscores the critical role of the distal fin distance (Scheme 1) in temperature control and PCM convection, highlighting its importance in the design process. In contrast, numerical results of the alternative fin layout (Scheme 2) reveal its unsuitability for PV cooling applications.

Influence of mass flux ratio and phase difference on impingement heat transfer characteristics of coaxial synthetic jet

The aim of the present study is to introduce and investigate the performance of a novel independently controlled coaxial synthetic jet (CSJ) designed for enhancing impinging heat transfer applications. The CSJ features a unique configuration with two coaxial cavities, each featuring inner and annular orifices of the same hydraulic diameter, all aligned at 0∘ The independently controlled CSJ allows precise manipulation of jet conditions and phase differences between its inner and outer cavities, offering a versatile platform for optimizing heat transfer performance under varying operational scenarios. This capability not only enhances our understanding of the heat transfer characteristics of the CSJ but also underscores its potential as an innovative tool for advancing thermal management in engineering systems. Here, the actuators are operated at a Reynolds number (Re) of 1260 to perform the jet impingement experiment. The study explores mass flux ratios, including 0.5, 1, and 2, to understand how these ratios affect impinging heat transfer characteristics. The investigation also explores the influence of different phase differences (∅) between the inner and outer diaphragms, ranging from 0∘ to 180∘ for different mass flux ratios. It has been observed that the percentage enhancement of the peak stagnation Nusselt number (Nustag) for Mr=0.5 is approximately 30.36░% and 53.68░% compared to Mr=1 and Mr=2, respectively. The peak Nustag enhancement of CSJ operated at Mr=0.5 is approximately 63.9░% and 58.6░% compared to the inner jet and annular jet operated separately. In the far field, when a phase difference of ∅=135∘ is provided, the peak Nustag is enhanced by approximately 17.29░% compared to ∅=0∘ for Mr=0.5. Based on the present study, it is recommended to operate the CSJ at a lower mass flux ratio (Mr=0.5) and a higher phase difference between the actuators (∅=135∘) to achieve maximum cooling effect from the heated plate.

Thermal management characteristics of a novel cylindrical lithium-ion battery module using liquid cooling, phase change materials, and heat pipes

To improve the thermal performance of large cylindrical lithium-ion batteries at high discharge rates while considering economy, a novel battery thermal management system (BTMS) combining a cooling plate, U-shaped heat pipes, and phase-change material (PCM) is proposed for 21700-type batteries. The effects of variables such as the contact angle between a corrugated aluminum plate (CAP) and the battery, the coolant flow direction in the cooling plate, the type of PCM, and the coolant flow velocity on the thermal characteristics of the batteries in the BTMS are investigated, and the advantages of this coupling cooling strategy relative to a single active cooling or a single active and passive cooling combination strategy are discussed. The results indicate that a corrugated aluminum plate is beneficial for significantly improving the temperature uniformity of the batteries. A staggered flow-direction scheme of adjacent channels significantly improves the temperature uniformity relative to the other inlet flow modes. The thermal performance of the batteries in the BTMS using paraffin and expanded graphite (PA/ EG) is superior to that with pure paraffin or paraffin and copper foam (PCF), with temperature uniformity improved by 44.6 % and 16.0 %, respectively. Increasing the coolant flow velocity can decrease the maximum temperature of the batteries and significantly reduce the heat dissipation share of PCM, resulting in a decrease in the temperature uniformity of the batteries in the BTMS. Meanwhile, compared with pure liquid cooling or a combination of liquid cooling and heat pipe or PCM, the proposed coupling BTMS not only reduces the maximum temperature of the batteries and further improves the temperature uniformity, but also significantly reduces the operating energy consumption of the BTMS.

Constructing multi-dimensional alternating layer nested structure for enhancing electromagnetic shielding, thermal management and strain sensing

It is imperatively desired to design excellent electromagnetic interference (EMI) shielding and thermal management simultaneously. Herein, fabricating the multi-dimensional alternating layer nested (MALN) structure composite film, which consisted of the alternating multilayer structure constructed by silver nanowires (AgNWs)/cellulose nanofiber (CNF) layer and the graphene nanoplates (GNPs)/CNF layer, the dense conducting networks built by interweaving AgNWs in CNF networks, and the “mille-feuille” structure of GNPs and CNF. The heterogeneous layers of AgNWs/CNF layer and GNPs/CNF layer with significant conductivity differences, as well as the “mille-feuille” structure of CNF and GNPs, provide abundant macro/micro heterogeneous interface polarization losses and multiple reflection losses. Adjusting the addition of AgNWs or GNPs in different layers to form the conductivity gradient, endowing the “absorption-reflection–absorption” loss path and excellent conduction loss of film. Therefore, the MALN structure composite film with a thickness of 90 μm exhibits an impressive EMI shielding efficiency (SE) of 98.95 dB and a specific SE (SSE/t) of 11606.14 dB/g·cm−2, attribute to its excellent conduction loss, abundant macroscopic/microcosmic heterogeneous interfacial polarization losses, multiple reflection losses, and the absorption-reflection–absorption loss path. Meanwhile, the in-plane thermal conductivity (λ∥) and out-plane thermal conductivity (λ⊥) achieve of 8.69 W/(m·k) and 0.16 W/(m·k). Additionally, the obtained film also demonstrates exceptional joule heating, remarkable photothermal conversion, outstanding mechanical properties, and distinguished strain sensing capabilities, which exhibiting significant potential in wearable electronic devices.

A novel approach for solidification enhancement of phase change materials through direct contact with a boiling fluid: An experimental investigation and visualization

Due to their remarkable properties, such as high latent heat and stable temperatures during phase transitions, phase change materials (PCMs) are widely used in thermal energy storage (TES) and thermal management systems (TMSs). However, their low thermal conductivity has limited their broader application across various industries. This study experimentally explores, for the first time, the effects of injecting boiling fluid (BF) into the PCM container as a new method to enhance heat transfer during the solidification process of PCM. To this end, Paraffin wax and acetone with saturation temperature lower than paraffin’s freezing point are selected as PCM and BF, and the influence of four various parameters, namely the initial PCM temperature (75, 85, and 95 °C), the height of the PCM inside the container (15 cm, 25 cm, and 35 cm), the flow rate of the BF (0.32, 0.46, and 0.57 L/min), and the nozzle diameter (2 mm, 3 mm, and 4 mm), on the solidification behavior of PCM, temperature distribution inside the container, and heat transfer enhancement (released energy and Nusselt number) is thoroughly scrutinized. In order to visualize and further evaluate the two simultaneous phase transitions (vaporization of the BF and solidification of the PCM), a Hele-Shaw cell with a height, width, and thickness of 50, 20, and 1 cm is considered as the PCM storage system. The findings indicate that when the BF is injected into the paraffin storage, the high heat transfer coefficient of boiling superbly improves the thermal behavior of PCM, and the solidification process occurs in a much shorter time. Also, boiling of the acetone inside the container and its direct contact with paraffin leads to a significant mixing inside the container and the creation of vortices and turbulent flow in the system, which further improves the freezing phenomenon. Furthermore, it was observed that regardless of other parameters, the flow rate of BF is the most crucial parameter, and after that, the height of the paraffin and the initial temperature have the greatest impact. By employing the highest flow rate, the proposed technique is capable of freezing 0.7, 0.5, and 0.3 L of paraffin in 48, 33, and 18 s, respectively, indicating multiple times of improvement in the full solidification time compared to previous studies.

Advancing cryogenic electronic cooling: A case study on embedded manifold microchannels in micromachined Joule-Thomson coolers

Thermal management plays a crucial role in the performance of electronic devices. For devices operating at room temperatures, manifold microchannels (MMCs) are essential for heat dissipation in heat sinks due to their low thermal resistance and pressure drop. However, their application in cryogenic electronic devices to enhance thermal performance has been largely unexplored. Herein, we integrated manifold microchannels into the evaporator of a micromachined Joule-Thomson (MJT) cooler to improve its cooling performance. The results show a notable reduction in the minimum cooling temperature from 105.0 K to 95.3 K, accompanied by an approximate 20 % increase in maximum cooling power. Furthermore, the coefficient of performance (COP) exhibits a rise of over 20 %. These findings underscore the feasibility and effectiveness of using MMCs in cryogenic electronic devices.

Analysis of charging performance of thermal energy storage system with graded metal foam structure and active flip method

The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is characterized by high energy storage density, small volume change, and constant operation temperature, which is widely employed in waste heat recovery, solar thermal utilization, and equipment thermal management. This paper introduces active flipping and graded porous to strengthen natural convection and heat conduction to alleviate the issue of low thermal conductivity and non-uniform phase change of PCM. Based on the fixed grid system, the enthalpy-porosity method combined with time-dependent gravity and non-Darcy porous effect is employed to solve the solid-liquid phase change problem under different porosity gradients, dimensionless flipping times (t*), and modified Ra (Ra*) numbers. Furthermore, the effects of the Ra* on the optimal t* and porosity gradient are also discussed. The results show that the flipping method can significantly enhance flow and heat transfer within the container, improve temperature field uniformity, and increase the proportion of latent heat storage. With the increase of porosity gradient and t*, the melting time initially decreases and then increases and the optimal thermal performance is achieved at a 6 % porosity gradient and t* = 0.4. Compared to the uniform porous structure without flipping, it can shorten melting time by 49.37 % and improve thermal energy storage rate (TESR) by 76.23 %. Additionally, the optimal porosity gradient is 6 % under different Ra*, but the optimal t* decreases with the increase of Ra*. This paper explores the charging performance of the thermal energy storage system with the graded metal foam structure and active flip method, which can contribute to the study of heat transfer enhancement in LHTES technology.

Indoor thermal energy optimization and 3D visualization based on ambient light sensing in the protection of historical architectural landscapes

While preserving cultural heritage, historic buildings also face the challenge of modern comfort and energy efficiency. Thermal energy optimization of indoor environment is an important means to improve living comfort and reduce energy consumption. Especially when protecting historical buildings, it is necessary to analyze how to carry out effective thermal energy management without affecting their appearance and structure. This paper discusses the optimization strategy of indoor thermal energy based on ambient light sensing technology, combined with 3D visualization to achieve the balance between energy conservation and comfort in historic buildings. Through the dynamic monitoring and analysis of indoor thermal environment, a feasible solution is provided for the protection and utilization of historical buildings. In this study, ambient light sensors were deployed in a historical building to monitor indoor light, temperature and humidity in real time. Through data collection and analysis, the main factors affecting indoor thermal environment are identified. 3D visualization technology is used to visualize the indoor heat energy distribution, and specific optimization suggestions are put forward. The research shows that the application of ambient light sensor significantly improves the monitoring accuracy of indoor heat energy, and the implementation of optimization measures reduces the indoor temperature fluctuation and energy consumption. The 3D visualization visually shows the thermal energy changes before and after optimization, providing a basis for managers to make decisions. Combined with 3D visualization technology, it not only enhances the comprehensibility of data, but also provides innovative ideas for the protection and rational use of historical buildings.

Neural network algorithms of a curved riga sensor in a ternary hybrid nanofluid with chemical reaction and Arrhenius kinetics

To improve the thermal management systems in industrial operations, there is a need for the prediction and complexity of advanced fluid motion across various physical conditions on different geometries. Further, ternary nanofluid flow across curved Riga surfaces plays a significant role in thermal management systems, chemical industries, thermal management systems, biomedical, environmental engineering, and more. Based on the above importance the current study focuses artificial neural network (ANN) model on the ternary nanofluid flow over a curved Riga surface in the presence of chemical reaction and activation energy. Proper assumptions and boundary layer approximation were used to develop the model. Using appropriate similarity variables, the governing equations are further simplified to ordinary differential equations (ODEs). Runge Kutta Fehlberg's 4th-5th order and shooting process are applied to solve the simplified equations. The primary objective is to improve the construction and optimization of thermal administration systems and other manufacturing procedures by gaining a deeper knowledge of the fluid motion and characteristics of heat transfer involved. Graphs are used to provide additional context for the important dimensionless constraints. The obtained data was utilized to train the ANN model, which was then verified towards numerical values of important engineering coefficients. The results reveal that the addition of solid volume fraction will enhance the thermal profile while declining the concentration profile. The reaction rate parameter will decline the concentration, and a reverse trend is seen for the activation energy parameter. The constructed model exhibits an outstanding degree of precision throughout the procedure, spanning all phases of the research.

3D printable phase change based thermal interface material with lower total thermal resistance at operating temperature

Thermal interface materials (TIMs) play a crucial role in addressing the heat dissipation challenges of electronic components, which needing high thermal conductivity and low thermal resistance to effectively improve heat transfer between chip and heat sink. This work focuses on the design of a 3D printable phase change based TIMs, which can be integrated with 3D printing technology to provide shapes suitable for quickly filling the gap between the chip and the heat sink in actual automated production. The optimized sample exhibits a total thermal resistance of 0.0012 m2K/W at operating temperature, with a through-plane thermal conductivity of 0.48 W/mK and an in-plane thermal conductivity of 1.24 W/mK. In practical thermal management, the resulting samples demonstrated a temperature reduction of 22 °C comparison with commercial TIM, highlighting its superior heat dissipation capability.

Enhancement and modulation of near-field radiative heat transfer in Bi2Se3/graphene-based three-body configurations

The manipulation of near-field radiative heat transfer (NFRHT) through complex photon tunneling in many-body systems has garnered significant attention, particularly for advancing thermal management in micro- and nanodevices. In this work, we theoretically investigate the enhancement and modulation of NFRHT within a graphene/Bi2Se3-based three-body configuration. Compared to a two-body configuration, the three-body modulator enhances the near-field radiative heat flux (NFRHF) by 2.77, primarily due to the enhancement of surface plasmon polaritons facilitated by graphene. Moreover, we analyze how NFRHF is modulated by varying the vacuum gap between the emitter and the intermediate, adjusting the thickness of Bi2Se3 films in emitter and intermediate, as well as manipulating the chemical potentials of graphene. Results indicate that by tuning the chemical potentials of graphene, thermal regulation can be enhanced up to a ratio of 2.55. This enhancement is attributed to the excitation of SPPs, which are concentrated in a narrower wave vector space and higher angular frequency range as the chemical potential of graphene increases. These findings have implications for controlling thermal radiation applications utilizing graphene and Bi2Se3 heterostructures. This work demonstrates the superiority of the three-body system in enhancing NFRHT and contributes new insights into the potential applications of Bi2Se3 in NFRHT.

Battery thermal management system by employing different phase change materials with SWCNT nanoparticles to obtain better battery cooling performance

Maintaining a stable temperature within a battery is essential for optimizing the performance of battery thermal management systems. Phase change materials (PCMs) have demonstrated potential in achieving this stability. This study investigates the use of single-walled carbon nanotubes (SWCNTs) dispersed in three PCMs with varying fusion temperatures to regulate the temperature of a lithium-ion battery (LIB) during discharge, a common scenario in electric vehicles. A Computational Fluid Dynamics (CFD) approach was utilized to simulate the liquid-solid transition of the PCMs, incorporating buoyancy forces in the liquid phase surrounding the LIB. The study examined the effects of different C-rates (1, 2, and 3), SWCNT volume fractions (0, 2, and 4 %), and three types of PCMs (RT27, RT35, and RT58) across multiple simulation scenarios to evaluate their impacts on LIB temperature and PCM melting fraction. Results indicate that nano-enhanced PCMs, which exhibit superior convection effects in the liquid phase, significantly enhance battery cooling performance. Specifically, at a C-rate of 1, using a 4 % volume fraction of nanoparticles in the PCM reduces the battery temperature by an average of 4.138 K compared to cases without nanoparticles. Additionally, while nanoparticles are generally reported to have a minor effect on cooling and melting processes, this study reveals that considering the beneficial effects of SWCNTs and the physical properties of the selected PCMs, the cooling performance of LIBs improves by 4.69 percentage points for the scenario with a C-rate of 3, RT58, and ɸ = 0.02. In this particular case, the melting process is more pronounced in the top half of the battery, where the increased velocity magnitude of the melted region contributes to enhanced battery cooling.

Optimal battery configuration for electrical vehicles in hot climates: A numerical comparative study of materials and cooling approaches

The battery plays a pivotal role in the electric vehicle (EV) sector, and the advancement of this industry hinges on enhancing the thermal performance and efficiency of batteries, especially in regions characterized by high-temperature extremes. The primary objective of this study is to propose a battery configuration capable of operating efficiently in hot regions. To achieve this goal, we have selected six battery materials, each possessing distinct physical characteristics, for an in depth investigation into their thermal behavior within a mini-channel Thermal Management System. Subsequently, we conducted a comparative analysis of various volumetric flow rates and flow directions to determine the optimal combination. Once the best configuration was identified, we conducted a case study using realistic ground-based meteorological data to evaluate the performance of the selected battery configuration under real conditions. The results of this study reveal that material which is characterized by the specific heat of 830J.kg-1.K-1, and a thermal conductivity of Kx = Ky = 34W.m-1.K-1 and Kz = 3.4W.m-1.K-1, exhibits the highest thermal performance. Taking into account the power required for the system, the most efficient volumetric flow rate is 0.05 L/min which requires a power of 3e-7W, with the same direction of fluid inlet and outlet in the minichannels. The selected material, volumetric flow rate, and flow direction in this study ensure that the maximum temperature of (Tmax) of the cell is maintained at 29.21 °C, with a temperature difference (Tdiff) of 1.56 °C. Regarding the case study, applying this optimal configuration under the climatic conditions of Benguerir, Morocco, results in a Tmax of 29.36 °C and a Tdiff of 1.58 °C, confirming the feasibility of the proposed battery configuration and its BTMS in high-temperature conditions.

Chaotic Behavior and Heat Transfer Analysis of Pulsating Flows with Different Frequencies

Due to the rapid development of electronic devices, the improvement of air–cooling methods for thermal management is urgent. In the present work, a promising way of coupling pulsating flow and vortex generators is proposed to eliminate the impacts of severe local high-temperature regions behind the vortex generators. Different from the traditional qualitative analysis, chaos is introduced to identify the quantitative impacts of the nonlinear dynamics of the coupling system. Particularly, the flow field was examined using the line stretching and the Poincaré map, and the chaotic characteristics of high-frequency pulsating flow were investigated. The results show that high-frequency pulsating flow enhances heat transfer mainly by promoting chaotic mixing. The chaotic fluid repeatedly stretches and folds, which increases the line stretching. Thus, the line stretching distribution can represent the heat transfer. Compared to the steady flow case, at Reynolds number of 1024 and pulsation frequency of 250 Hz, pulsating flow improves the Nusselt number by 5.82% and reduces friction factor by 2.62%, resulting in an improvement of thermal performance factor by 6.76%.

Adjustable temperature and high thermal conductivity composite phase change material based on sodium acetate trihydrate–alanine/expanded graphite for thermal management of electronic devices

Phase change energy storage technology using phase change materials (PCMs) is a viable solution to effectively address the heat dissipation problems of electronic devices. Herein, we proposed to prepare a modified PCM using CH3COONa·3H2O (SAT) as main PCM, 9 wt% DL-Alanine (DL) as temperature modifier, and 2 wt% Na2HPO4·12H2O as nucleating agent. Calculations using density functional theory method confirmed that the adjustment of DL on phase change temperature of SAT was originated from the hydrogen bond between them. Then, the modified PCM was loaded into 14 wt% expanded graphite (EG) to obtain a composite PCM with a suitable phase change temperature of 52.9 °C, phase change enthalpy of 227.4 J/g as well as supercooling degree of 6.6 °C, and the thermal conductivity of the composite PCM was as high as 11.52 W·m−1·K−1. SEM and pore structure analyses showed that the modified PCM was successfully loaded into the pore structure of EG, and their combination was verified by XRD and FT-IR as a physical interaction. After 200 heating–cooling cycles, the phase change temperature and enthalpy of the composite PCM was basically unchanged along with consistent crystal structure and chemical composition, showing an excellent thermal reliability. A comparative analysis applied in a testing system showed that with loading of the composite PCM temperature control module, the critical time of the electronic chip was extended by 4670 s and the thermal equilibrium temperature was decreased by 20.4 °C, presenting a good thermal management performance. Therefore, the prepared composite PCM had great potential for application in thermal management of electronic devices.

Simulation study of flow and heat transfer in wavy microchannel heat sink with manifolds and secondary channels composite

With the continuous increase in power density of electronic devices, traditional cooling methods have gradually shown their limitations. Microchannel heat sinks (MCHSs) have enormous potential in thermal management for electronic devices due to their excellent heat dissipation performance. To improve the flow and heat transfer performance of MCHSs, a numerical study was conducted on 56 types of wavy microchannel heat sinks with manifolds and secondary channels composite (WMCHS-MSCs). The results indicate that compared to the original manifold wavy microchannel heat sink (MWMCHS), the optimal WMCHS-MSC increases the thermal enhancement factor by 45.1 % when the inlet volume flow rate Q = 1.0 × 10−6 m³/s. At the same time, the overall thermal resistance, the maximum temperature difference on the bottom wall, and the pressure drop of the optimal WMCHS-MSC are reduced by 7.6 %, 21.9 %, and 10.6 %, respectively. Compared to the original MWMCHS, the increase in Q for WMCHS-MSCs results in an overall trend of increased thermal performance, decreased temperature non-uniformity and hydraulic performance, and initially increased and then decreased overall performance. The flow field distribution of the secondary channels of WMCHS-MSCs intuitively demonstrates the improved hydraulic and thermal performance brought about by disrupting the thermal boundary layer and mixing the flow. The study presents a novel approach for the design of wavy MCHSs, potentially paving the way for enhanced thermal management solutions in electronic devices.

Indoor space thermal cycle design and animation 3D modeling based on digital light processing technology

With the continuous development of architectural design concepts, the thermal cycle optimization of interior space has become an important topic to improve energy efficiency and comfort. The introduction of digital light processing (DLP) technology provides new possibilities for 3D modeling and thermal cycle analysis. This study uses digital light processing technology to design and optimize the thermal cycle of indoor space, and explores its application in real-time animation 3D modeling to provide a more intuitive visual display. DLP technology is used to build a three-dimensional model of interior space, and heat flow analysis software is combined to simulate the thermal cycle of different design schemes. The dynamic simulation method was used to analyze the change of heat circulation in the exhibition room and its influence on the indoor environment. The results show that the indoor thermal cycle optimized by DLP technology can effectively improve the heat distribution uniformity and energy efficiency utilization, and the simulation results show that the improved scheme has significant advantages in thermal comfort. This study proves the feasibility and effectiveness of digital light processing technology in indoor space thermal cycle design, and provides a new idea for future architectural design and thermal cycle management.

Multi-objective optimization and artificial neural network models for enhancing the overall performance of a microchannel heat sink with fins inspired Tesla valve profile

Microchannel heat sinks (MCHSs) are advanced cooling systems used in various applications such as electronics cooling, thermal management of high-power microprocessors, and microelectronic devices. These heat sinks are designed to efficiently dissipate heat generated by electronic components to maintain optimal operating temperatures and ensure device reliability. Employing appropriate fins within MCHSs is a crucial strategy to enhance heat removal efficiency. Since few investigations have been performed on the simultaneous thermo-hydraulic features in microchannels with Tesla valves, this research addresses this gap by suggesting that the microchannels of a heat sink be reinforced with novel Tesla valve-shaped fins. Tesla valves are designed to offer different levels of resistance depending on the flow direction. This characteristic allows for selective control of pressure drop and heat transfer efficiency by simply switching the flow direction. Utilizing Tesla valve-shaped fins is an almost new approach that differentiates the current research from conventional designs. The advantage of this structure is that under different circumstances, depending on whether more heat transfer is required or less pressure drop (ΔP), the flow direction can be changed, and the maximum efficiency of the MCHS can be accessed. The other innovative aspect of this study lies in the integration of artificial neural network (ANN) models to optimize the efficiency of MCHSs equipped with Tesla valve-shaped fins. The simulations were conducted to characterize the flow and thermal features of the MCHS. Then, these data were used as the benchmark for training the ANN models. Four ANN models were introduced to anticipate the Nusselt number (Nu) and ΔP in each forward and reverse direction. The divider's acute angle (α), the divider's obtuse angle (β), and the divider's radius (R) were selected as the input data. Multi-objective optimization and genetic algorithms were used to achieve the optimal conditions. In the optimal thermal design (Setting 2: MCHS with fin variables of α = 60 β = 180, and R = 80 μm in reverse flow direction), the overall performance had a significant enhancement of 57.1 % compared to the device lacking fins. Furthermore, in Setting 2, the overall performance of the MCHS and its diodicity experienced notable improvements of approximately 12.1 % and 38.5 %, respectively. Implementing the parameters of Setting 5 (MCHS with fin variables of α = 60, β = 152.32, and R = 73.10 μm in forward direction) during fin production resulted in a notable enhancement of about 41.1 % in the device's overall performance.

Piezoelectric micropump cooler for high-power electronic cooling

Micro-liquid cooling is highly effective for the thermal management of electronic chips. However, it is challenging to apply to high heat flux and compact electronic devices because of the limited cooling power and large pump volume. To address this issue, a compact piezoelectric micropump cooler (PMC) integrating a parallel piezoelectric micropump (PPMP) and a heat sink with a fluid guidance structure is designed. The flow and heat transfer performance of the PMC is theoretically optimized through a numerical coupling model considering mechanics, flow-solid heat transfer, and piezoelectric effect. Simulation results suggest that a copper electrode-PZT ratio of 1.4 increases the output flow rate of the PMC, and the design of five fluid guidance structures enhances its heat dissipation effectiveness. Based on the optimized results, the PMC prototype is manufactured employing 3D printing technology. Experimental results show that the flow rate maximum is 62 mL/min with a precision of 0.07 mL/V·min. When the flow rate of PMC increases to 50 mL/min, the temperature of a heat source with 50 W/cm2 can be reduced to 57 °C, which is comparable with the simulation value. The developed model accurately characterizes the heat transfer properties of the PMC thermal management approach, providing a valuable reference for future research. The proposed PMC is characterized by its compact size, high level of integration, and exceptional cooling performance, making it suitable for electronic cooling applications with high heat flux.