International Journal of Heat and Mass Transfer最新文献_第7页

Silicon cylinders hollowed for nonreciprocal thermal radiation under a magnetic field of 1 T

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126738

Xu Huang , Bo Wang , Jinyun Zhou , Jing Ye

Nonreciprocal thermal radiation represents an innovative approach to radiative heat transfer that overcomes the symmetric reciprocity constraints imposed by Kirchhoff's law. However, most existing nonreciprocal thermal radiation devices are limited to single polarization and typically necessitate large angles and significant magnetic fields. This paper presents a dual-band dual-polarization nonreciprocal thermal emitter made up of periodic arrays of silicon cylinders hollowed, a magneto-optical material layer, and a metallic plate. Rigorous coupled-wave analysis is employed to examine the structural parameters and the efficiency. Results demonstrate that the efficiencies of the two nonreciprocal bands for transverse electric (TE) and transverse magnetic (TM) polarizations exceed 90 % when subjected to a 1 T magnetic field and an incident angle of 5°. The underlying physical mechanism of strong nonreciprocity is elucidated through an investigation of coupled mode theory and the distributions of electromagnetic fields. Additionally, the validity of the computational results is corroborated using the finite element method. Furthermore, the impact of various parameters on nonreciprocity is analyzed. Compared to traditional nonreciprocal thermal emitters, the proposed emitter effectively reduces reliance on both magnetic field strength and incident angle, significantly enhancing its practical applicability in the field of energy harvesting.

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引用次数: 0

Simultaneous topology optimization of two hydraulically interconnected porous flow layers in cold plates

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126671

Abhijeet Banthiya, Bruno Navaresse, Liang Pan, Justin A. Weibel

Cold plate topology optimization is a focus area of research in thermal management, often approached with simplified two-dimensional models to maintain the low computational costs needed for iterative design. However, embracing higher dimensionality in optimization can yield significant performance enhancements, as exemplified by cold plate architectures like manifolded microchannels. In this study, we present a novel 2.5D topology optimization framework tailored to two-flow-layer manifold cold plates, leveraging the homogenization approach to topology optimization. Under this framework, multiple stacked flow layers are simultaneously optimized within a 2D stack while considering local mass and energy exchange between them, enabling the design of intricate 3D flow geometries with the computational efficiency of 2D simulations. The mass and energy exchange between the layers is governed by the optimizable inter-layer flow resistance. This approach is demonstrated for a test case with two coupled flow layers between enclosing solid substrates heated from their external surfaces. The homogenization approach is used to define the local design variables in these layers based on the physical porosity of microstructures (viz., square pin-fins) and the inter-layer coupling within computational cells. A multi-objective cost function, encompassing total pressure drop and thermal resistance, guides the optimization of the microstructure distribution in each layer, resulting in a Pareto front of designs illustrating the balance between these two competing objectives. Full-scale, high-fidelity 3D flow simulations were performed on the topology-optimized two-flow-layer cold plate to validate results from the homogenized 2D simulations. The calculated flow fields showed good agreement between low-cost 2D simulations and high-fidelity 3D simulations, demonstrating the accuracy of the approach. The study provides valuable insights into the topology optimization of multi-layer cold plates, highlighting the potential for enhanced performance via higher dimensionality, as well as manufacturability through the homogenization approach.

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引用次数: 0

Characteristics of thermal runaway and propagation for 18650 lithium batteries in top-confined space

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126663

Juan Yang , Jiacheng Tong , Yu Yang , Qingsong Zhang , Jianghao Niu

Lithium-ion batteries (LIBs) are usually used in a narrow space, which can cause serious fire accidents if thermal runaway (TR) occurs. However, few studies have investigated the effect of top-confined space on LIB's jet fire as well as thermal runaway propagation (TRP). In this work, the top-confined space was constructed using top baffle, and a battery module for heat transfer analysis was constructed using aluminum columns with refractory ceramic fibre (RCF). Collected the data of the whole thermal runaway process of the battery module in the top-confined space. The behaviours of TR ceiling jet fire under different heights of baffle have been divided into three stages. Confirmed the effect of early-produced gas being ignited on TRP. Innovating a kind of calculate method of heat release ratio (HRR) under top-confined space. Calculated the amount of battery being heated during ceiling jet fire process. Summarised the effect of baffle height on thermal runaway propagation. The results show that 3cm or less between the baffle and batteries can lead to a violent combustion stage which does not present at other heights of baffle. The HRR of this stage is at least 5 times higher than the stable combustion stage. When the distance between the baffle and batteries is increased from 1 to 3cm, the percentage of heat transfer from the ceiling jet fire decreases from 60.3 % to 24.3 %, and the percentage of heat transfer between batteries increased from 14.2 % to 61.6 %. When the distance between the baffle and batteries is 2cm or less, TRP time is at least 1.7 times higher than other heights of baffle, as well as reduce the intensity level of TR for the propagated battery.

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引用次数: 0

Effect of surface wettability on bubble dynamics and heat transfer in microchannel flow boiling

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126729

Yanhong Sun , Zan Zhang , Guotao Zhang , Yuyan Jiang , Jun Zheng

Despite extensive studies and modeling of bubble dynamics manipulation in macroscale boiling, the effect of surface wettability on the bubble dynamics of microchannel flow boiling has seldom been investigated. The confinement of the microchannel and fluctuations in the dominant forces lead to unique confined bubble growth and distinctive bubble detachment. Surface wettability can significantly affect the bubble dynamics parameters, thereby influencing the heat transfer performance of microchannel flow boiling. In this study, we conducted subcooled flow boiling experiments and flow visualizations to quantitatively investigate the influence of surface wettability on sliding bubble dynamics, confined bubble growth, and heat transfer characteristics in a microchannel using HFE-7100 as the working fluid. Numerous nucleation sites were activated owing to the lower energy barrier for bubble nucleation on the hydrophobic surface. The elongated bubble shape was flatter, and the bubble size was larger, which could be attributed to the strong bubble adhesion force on the hydrophobic surface. The bubble sliding and growth velocities were much higher on the hydrophilic surface, and bubble acceleration increased the shear stress and pressure gradient surrounding the bubble, producing a more non-axisymmetric oblique triangle profile of the elongated bubble. The bubble growth rate on the hydrophilic surface was approximately three times higher than that on the hydrophobic surface. The heat transfer coefficients (HTCs) on the hydrophobic surface increased by up to 82 % and 25 % during microchannel flow boiling at mass fluxes of 112 and 230 kg·m⁻²·s⁻¹, respectively, because of the activation of numerous bubble nucleation sites. Furthermore, the HTCs increased by up to 56 % for higher mass fluxes owing to the strengthening of microconvection and suppression of annular flow. The nucleate boiling mechanism dominated the microchannel flow boiling heat transfer.

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引用次数: 0

Improving FEM-based solid mechanics simulations for ultrashort pulse laser ablation by integrating an equation of state and material separation

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126714

David Redka , Julian Vollmann , Jan Winter , Michael Schmidt , Ján Minár , Heinz Paul Huber , Philipp Schmid

Accurate simulations are paramount for deepening our understanding of ultrashort pulse laser ablation, a complex process involving non-equilibrium thermal and material transport on time-scales spanning several orders of magnitude. In response to this need, we propose a novel approach that enhances the use of a readily available finite element method tool for multiphysics simulations by incorporating an equation of state (EOS). This new model, termed the two-temperature solid mechanics model including EOS (SM-EOS), has been meticulously tested against isostatic changes and compared with an experimentally validated two-temperature hydrodynamic simulation (HD). Further comparison was made with classical TTM solid mechanics (SM-ISO) simulations using constant or isobaric material parameters. A mechanism for describing material separation due to spallation is also incorporated in the model. Bulk aluminum serves as prototype within this investigation. Our results show that SM-EOS aligns closely with HD, significantly outperforming the classical SM-ISO simulations. Given its robust performance and ease of implementation, our SM-EOS model is expected to serve as a valuable tool for both research groups and industrial applications, thereby facilitating further investigations into ultrashort pulse laser ablation phenomena. Furthermore, it is expected that our approach could influence other fields in simulating phase transitions and extreme states of matter utilizing solid mechanics calculations.

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引用次数: 0

Experimental study on the effect of hydraulic diameter on the flow boiling characteristics in microchannels

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126736

Zheng Zhang , Guanmin Zhang , Yi Zhang , Maocheng Tian

Microchannel flow boiling heat dissipation has emerged as an effective solution for managing high heat flux in electronic devices. The hydraulic diameter of microchannels plays a crucial role in influencing flow boiling characteristics and heat sink design, yet the relationship between hydraulic diameter and flow boiling remains inadequately explored. This study employs a visualization-based experimental system with six distinct channel diameters (250 μm -1500 μm) to examine the effects of hydraulic diameters on microchannel flow boiling heat transfer characteristics. In this study, the number of microchannels was three, the working fluid was deionized water, the heat flux ranged from 203 to 880 kW/m², the system outlet pressure was 101.325 kPa, the pressure drop ranged from 0.71099 to 18.021 kPa, and the vapor quality ranged from 0.00183 to 0.37536. Results indicate that variations in microchannel hydraulic diameters lead to significant changes in flow patterns, heat transfer coefficients, and pressure drops. At a hydraulic diameter of 250 μm, annular flow forms earlier but is more prone to dry out. The heat transfer coefficient increases progressively as the hydraulic diameter is reduced. When the heat transfer coefficient enters a relatively stable change, a hydraulic diameter of 1500 μm yields a heat transfer coefficient ranging from 15 to 30 kW/m²·K. Reducing the hydraulic diameter to 750 μm increases the heat transfer coefficient to a range of 40–60 kW/m²·K, while further reducing the hydraulic diameter to 250 μm elevates the heat transfer coefficient to between 65 and 90 kW/m²·K. Pressure drop is highly sensitive to hydraulic diameter, with channels under 500 μm exhibiting the highest values and more pronounced slope variations. The pressure drop decreases as the hydraulic diameter increases. Due to inertial forces, larger hydraulic diameters induce more significant fluctuations in pressure drop and wall temperature during backflow. Through Spearman correlation analysis, this study fits heat transfer and pressure drop friction coefficients adaptable to different hydraulic diameters. This work offers theoretical insights and practical design guidance for optimizing microchannel heat sinks.

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引用次数: 0

Characterising and modelling plasma transferred arc for additive manufacturing

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126735

Guangyu Chen, Yongle Sun, Chong Wang, Jialuo Ding, Wojciech Suder, Zhiyong Li, Stewart Williams

The thermal characteristics of a plasma transferred arc (PTA) and its mathematical representation are primary considerations when designing and modelling PTA-based wire arc additive manufacturing (WAAM). However, most of the currently used PTA thermal characteristics are derived from welding processes, which are not directly applicable to WAAM. In this study, the power density distribution, arc diameter and arc efficiency of PTA in the WAAM process were measured using the split anode calorimetry (SAC) method. The effects of key process parameters, including current intensity, plasma gas composition, plasma gas flow rate, and arc length, on the PTA power profile were systematically examined. The results show that for a typical PTA used in WAAM, the arc diameter ranged from 9.6 mm to 10.8 mm, with an arc efficiency of approximately 60 % within the tested parameter range. The PTA power becomes more concentrated as power density increases with higher current intensity and plasma gas flow rates. Additionally, a softer plasma was achieved by increasing helium content in the plasma gas or by using a longer nozzle-to-workpiece standoff distance, both of which are beneficial for avoiding keyhole defects. To accurately represent PTA power distribution, a binomial Gaussian heat source model was proposed, which captures the details of the arc power profile with a high accuracy of over 99.94 %, outperforming the conventional monomial Gaussian heat source model. The PTA calorimetry characterisation and the proposed binomial Gaussian model can be useful in establishing a better understanding of the PTA power profile and enhancing process control for high-precision WAAM.

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引用次数: 0

Numerical investigation of flow film condensation over an inline arrangement of two cylinders in the combined natural and forced convection regime

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126712

Rohit Kumar, B. Premachandran

The problem of flow film condensation over an inline arrangement of two cylinders is studied using three-dimensional numerical simulations. The interface evolution, the flow, and the heat transfer characteristics have been investigated using varying flow and geometrical parameters. The condensate removal from the top cylinder is mostly in the form of individual droplets. However, a liquid column develops between the cylinders as the condensate from the top cylinder is drained to the bottom cylinder. The number of droplet formation sites increases considerably as the cylinder diameter increases. As the cylinder diameter is decreased, the interface evolution pattern between the cylinder changes from individual droplets to a combination of liquid sheets and droplets. Furthermore, the condensate removal pattern from the top cylinder to the bottom cylinder changes from a combination of droplets and liquid columns to stable liquid columns as the wall subcooling increases. Additionally, the effect of different parameters on film condensation is also assessed in terms of the different quantitative results, such as the dimensionless liquid film thickness, dimensionless departure diameter of liquid droplets, dimensionless location of the breakup point of the liquid column between the two cylinders and the space–time-averaged Nusselt number.

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引用次数: 0

Analytic thermal conductance for square channel, flat plate oscillating heat pipe: CFD simulations of Taylor liquid film and experiment

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126711

Fan Lu , Lorenzo Franceschetti , Kyle Krippner , Massoud Kaviany , Takuro Daimaru

In oscillating (pulsating) heat pipes (OHP, PHP), square channels offer fabrication simplicity (e.g., 3-D printing) and have shown improved thermal performance over circular channels. It has also been suggested that the peripheral averaged slug-deposited liquid film thickness for square and circular cross sections are similar, though the presence of the corners alters the fluid dynamics significantly. Here, using isothermal CFD, the axial development of the Taylor liquid film behind a passing liquid slug in the square capillary channel is predicted. The results show that the film thickness varies peripherally and axially. The heat transfer in the evaporator is simulated by non-isothermal CFD and is dominated by liquid film evaporation. This liquid film conductance is inversely proportional to the peripheral-varying thickness. An analytic, upper-bound OHP thermal conductance is proposed based on an effective liquid film thickness,

G_{δ_{l}} = \frac{k_{l}}{δ_{l, s c, c}} {(\frac{1}{A_{e}} + \frac{1}{A_{c}})}^{- 1}

. In a companion experiment, a 3-D-printed square-channel (side dimension of 1 mm) flat-plate OHP (FPOHP) using R-134a as the fluid is tested, and the measured conductance is compared with the predicted upper bound. In FPOHP, the heat conduction between adjacent channels negatively affects the conductance; however, this effect is compensated by enhanced internal conductance. An existing 1-D heat-mass-momentum conserved simulation is extended to the square channel geometry and used to assess this 3-D plate conduction. A reasonable agreement (up to 80 percent) was found between the experiments and the simple, analytic upper-bound OHP thermal conductance.

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引用次数: 0

Novel model for heat transfer and flow correlations of precooler, preheater and regenerator in supercritical CO2 Brayton cycle

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Heat and Mass Transfer

Pub Date : 2025-01-23 DOI: 10.1016/j.ijheatmasstransfer.2025.126739

Xin Wang , Lingxiao Yang , Bo Xu , Zhenqian Chen

Existing studies have not comprehensively incorporated actual operating conditions of precooler, low-temperature regenerator (LTR) and high-temperature regenerator (HTR) in S-CO₂ Brayton cycle. Additionally, while progress has been made, developing tailored correlations for specific conditions remains an area requiring further exploration. The novelty of this work lies in the combined experimental and numerical approach that provides insights into the heat transfer and flow behavior across a wide range of actual operating conditions. The findings demonstrate that heat transfer coefficient in precooler and regenerator decreases and increases as inlet pressure rises, respectively. Notably, average heat transfer coefficient on cold side of the LTR is approximately three times that on hot side of the LTR at same Reynolds number. After incorporating wall temperature as a factor in our considerations, the heat transfer correlation are developed for the precooler that yields a prediction accuracy of 99.5 % for numerical data, with an error margin controlled within ±20 %. However, when the influence of wall temperature is disregarded, the prediction accuracy remains at 94.2 %, with an error margin still maintained within ±20 %. Additionally, the integration of these correlations and models with advanced optimization techniques can enable development of optimal S-CO₂ system configurations.

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引用次数: 0