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International journal of heat and fluid flow
Mechanical Engineering Publications Ltd.
International journal of heat and fluid flow

Mechanical Engineering Publications Ltd.

0142-727X

International journal of heat and fluid flow/Journal International journal of heat and fluid flowSCI
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    Modulation of the local mass and heat transfer of turbulent double-diffusive convection under stable thermal stratifications

    Kenjeres S.Roovers R.
    1.1-1.13页
    查看更多>>摘要：© 2024 The Author(s)We report on numerical studies of bounded double-diffusive turbulent convection, which involves the combined effects of concentration/solutal and thermal buoyancy forces. Our study focuses on an intermediate range of the characteristic non-dimensional numbers, specifically 107≤Rac≤109, and 0≤Raθ≤106. We use fixed values for the concentration and temperature Prandtl numbers (i.e. Prc=700, Prθ = 7), which approximately correspond to seawater properties. We apply wall-resolved Large Eddy Simulations (LES) and compare the obtained results with available Direct Numerical Simulations (DNS) in the literature. Our findings show an overall good agreement in predicting the global wall mass and heat transfer coefficients, achieved with significantly reduced computational costs. Furthermore, the local mass and heat transfer distributions reveal a high sensitivity to the strength of the vertically imposed stable thermal stratification. Finally, we present the vertical profiles of the long-term time-averaged first and second moments.
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    • Elsevier

    Experimental and numerical investigation into the effects of spline mid-passage gap on endwall film cooling performance and aerodynamic characteristics

    Lu Y.Liu Z.Feng Z.Ye J....
    1.1-1.12页
    查看更多>>摘要：© 2024 Elsevier Inc.The coolant leakage flowing out from the mid-passage gap has been proved to offer an extra cooling to the endwall surface and was investigated by many scholars. While most studies focused on the straight mid-passage gap. In this paper, different types of spline mid-passage gap were introduced and studied experimentally and numerically, with the mass flow ratio ranged from 0.5% to 1.5%. Pressure sensitive paint technique was adopted to evaluate the film cooling performance, and numerical simulation was carried out to predict the aerodynamic performance. The results showed that compared to straight mid-passage gap, spline mid-passage gap can obviously improve the film cooling performance, and the curvature of the spline mid-passage gap will affect the peak value of the film cooling effectiveness and area of the coolant coverage. Back point case can achieve the maximum value of film cooling effectiveness, while center point case can achieve widest coolant coverage. What's more, Back point case will also lead to larger aerodynamic loss and center point case can obtain better cooling-aerodynamic performance at a larger mass flow ratio.
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    • Elsevier

    Pseudo three-dimensional topology optimization of chip heat sinks with various inlet–outlet arrangements

    Huang J.Chen B.Jiao K.Wang Q....
    1.1-1.16页
    查看更多>>摘要：© 2024 Elsevier Inc.Topology optimization (TO) represents a significant advancement in heat sink design for microelectronic chips. Although two-dimensional (2D) TO is favored for its simplicity and lower computational cost, it lacks the accuracy of three-dimensional (3D) TO, omitting certain processes inherent to 3D models. This paper introduces a novel pseudo 3D TO model, which integrates a 2D thermo-fluid design layer with a 2D conductive base plate layer, specifically optimized for chip heat sink designs. Employing the variable density method, we establish a mathematical description of the pseudo 3D TO, incorporating governing equations for flow dynamics and temperature variations in both layers. A distinctive feature of this model is its consideration of thermal coupling in the dimension typically neglected by standard 2D TO models. We applied the pseudo 3D TO model to optimize heat sink structures across various inlet and outlet configurations, followed by rigorous analyses to compare flow and heat transfer performances. These comparisons offer critical insights into the advantages and trade-offs of each configuration. Ultimately, a 3D heat sink was reconstructed from the pseudo 3D optimization results, and a detailed numerical experiment was conducted to assess its thermal performance under realistic conditions, thereby validating the efficacy and reliability of the pseudo 3D TO model. The findings underscore the model's potential in achieving efficient and practical heat sink designs, balancing accuracy and computational efficiency.
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    • Elsevier

    Visual boiling experimental research based on lateral liquid supply structure

    Li F.Xia G.Li R.
    1.1-1.10页
    查看更多>>摘要：© 2024 Elsevier Inc.The high heat transfer coefficient and critical heat flux density of thin liquid film boiling provide new ideas for enhancing boiling heat transfer, but the bottom-up liquid supply method limits its further application and development. This study is based on the experimental research results of previous researchers and adds lateral liquid supply while maintaining a lower liquid level. And thin liquid film boiling experiments were conducted on the surface of silicon under low subcooling conditions (subcooling degree: 5 K). The obtained curves were compared with the results of smooth copper surface in pool boiling experiments. Among them, thin liquid film boiling exhibits excellent HTC and higher CHF (12.26 W/cm2·K and 191.63 W/cm2, respectively). Then, the bubble behavior and flow characteristics of thin liquid film boiling bubbles were visualized and the heat transfer mechanism was analyzed. The experimental results indicate that the lateral liquid supply boiling structure designed in this study has great potential for application.
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    • Elsevier

    Hydrothermal performance enhancement of heat sink using low flow-drag twisted blade-like fins

    Ji, ShoutongHuadan, CairangQi, PanLiu, Zhenwei...
    1.1-1.20页
    查看更多>>摘要：To prevent power equipment from breaking down due to overheating, an innovative design of twisted blade-like fins for heat sinks is proposed to enhance heat transfer efficiency and minimize pressure drop. The effects of the twist angle and different NACA airfoil cross-section of fins on the flow and heat transfer characteristics are investigated using numerical simulation methods over a Reynolds number range of 8548 to 34194. Comparing the twisted blade-like fins with cylindrical fins, the relative Nusselt number is 1.067-1.397, the relative friction coefficient is 0.528-1.339, and the hydrothermal performance factor (HTPF) is 1.155-1.552. The results demonstrate that the novel twisted blade-like fins substantially outperform cylindrical fins in terms of comprehensive thermal performance. Furthermore, the optimal design in the study is compared with the best design in similar studies, and the results show that the optimal twisted blade-like fins exhibit better advantages in drag reduction performance and HTPF. When Reynolds number is 34194, the twisted blade-like fins provide the highest HTPF of 1.552. The twisted blade-like fins stimulate spanwise and normalwise secondary flow, promoting fluid exchange between the wall and the channel core, thereby enhancing the heat transfer performance of the heat sink. Increasing the twist angle will improve heat transfer efficiency but increase pressure drop. Different cross-section shape can have different effects, and using NACA0009 airfoil cross-section yields better results in most cases. The twisted blade-like fins are effective in the field of heat transfer enhancement with low flow resistance of streamlined structure and strong heat transfer effect of secondary flow, greatly improving the comprehensive thermal performance of the heat sink.
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    • Elsevier

    Investigation of free and impinging jets using generalized k–ω (GEKO) turbulence model

    Ganatra K.A.Chattopadhyay H.Mathur A.
    1.1-1.19页
    查看更多>>摘要：© 2024 Elsevier Inc.The present numerical study focuses on a novel generalized k–ω (GEKO) turbulence model. The model has unique feature of tunable free model parameters Cmix (mixing) and Cjet (jet) applicable for free jets along with Csep (separation) and Cnw (near wall) used for impinging jets. The slot and circular free jets and impinging jets are employed to assess the model's consistency in multiple flow aspects. The impinging surfaces are flat plate and cylinder and air is working fluid. Parameters such as velocity, turbulence intensity, turbulence viscosity ratio and Nusselt number are investigated for free and impinging jets. The free parameters have specific range where Cmix = 0.15–0.95, Cjet = 0–1, Csep = 0.7–2.5 and Cnw = − 2 to 2. The numerical results from Cmix = 0.2 for circular jet, Cmix = 0.3–0.4 for slot jet; Cjet = 0.9 and Cnw = 0.5 for both jet configurations are consistent with existing literature. Csep = 1.75 for slot jet whereas Csep = 1–2.5 for circular jet are considered as ideal for numerical prediction. The GEKO turbulence model offers additional feature of production limiter which prevents turbulence increment in stagnation region for impinging jets. Therefore in present study over prediction of numerical heat transfer than experimental is limited to 35 % whereas previous studies have reported it as high as 300 %. Moreover, the GEKO turbulence model is compared with high cost Large Eddy Simulation (LES) which shows excellent numerical competency with LES.
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    • Elsevier

    Influence of inclined magnetic field on mixed convective cross flow across a cylinder with uniform heat flux condition

    Saha R.Raju B.H.S.
    1.1-1.15页
    查看更多>>摘要：© 2024 Elsevier Inc.This numerical study delves into the interplay between inclined magnetohydrodynamic flow and mixed convective heat transfer in a cylindrical geometry under uniform heat flux condition. The study employs a quasi-static model, where the fluid is flowing in a cross-stream regime, satisfies the Boussinesq approximation. A higher-order finite difference scheme is adopted to discretize the non-linear Navier–Stokes and energy equations, followed by a stable pseudo-time iterative technique. This study reveals that a lower Richardson number and interaction parameter are sufficient to induce vortex shedding under positive magnetic angles that can not be achieved in case of aligned magnetic field. Increasing the strength of magnetic field tends to restore the symmetric flow structure from the buoyancy-driven asymmetric one, contingent upon the magnetohydrodynamic flow orientations. The coefficients of viscous and pressure drag, average Nusselt number become non-monotonic for the aligned magnetic field, whereas it becomes strictly monotonic for other positive magnetic inclination angles at each Richardson number. Interestingly, increasing magnetic inclination angle allows to augment the total drag coefficient and overall heat transfer drastically. Critical interaction parameter is determined for average Nusselt number at various Richardson and Reynolds numbers under aligned magnetic field. The heat transfer is significantly more enhanced under uniform heat flux condition compared to constant wall temperature condition. The enhanced heat transfer achieved through magnetic field integration and modified thermal conditions has significant potential for applications such as electronic cooling, solar collectors, material processing, and more.
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    Preparation and characterization of modified steel slag-based composite phase change materials

    Yang C.Zhang Z.Yu H.Xu N....
    1.1-1.8页
    查看更多>>摘要：© 2024 Elsevier Inc.In order to promote the resource utilization in steel slag and reduce the environmental hazards caused by steel slag, a steel slag-based composite phase change material was prepared in this experiment. Steel slag had a porous structure with good structural stability, which could be used to prepare composite phase change materials and applied in fields such as thermal energy storage and waste heat recovery. To enhance the adsorption capacity of steel slag on phase change materials, the impact of acid or alkali modifiers on steel slag was meticulously examined. The investigation revealed that the pore structure of the modified steel slag was markedly enhanced, accompanied by a notable improvement in adsorption capacity. Among the results, the adsorption rate of the acid washed modified steel slag for paraffin reached 35 %, with the phase change temperature and latent heat of phase change being 53 °C and 60 J/g. Acid washing had a significant impact on the pore structure of the steel slag, with the adsorption rate of the acid washed modified steel slag for paraffin being approximately twice that of the unmodified steel slag.
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    • Elsevier

    Enhancing heat and moisture transfer of porous fabrics using arrayed opposed jets: Experimental and numerical investigations

    Dai J.-A.Diao Y.F.Zhang L.
    1.1-1.14页
    查看更多>>摘要：© 2024Achieving rapid fabric drying and ensuring a uniform distribution of surface temperature and moisture is essential for the post-processing stage in printing and dyeing. Although jet technology is commonly used to enhance heat transfer processes, the mechanism of heat and moisture transfer using array opposed jet for fabric drying is still unclear. This paper proposes that using opposed jet to enhance the drying process for four different fabric structural types, the influence of jet Reynolds number and excess temperature on the change of fabric moisture content was analyzed using experimental methods, then by defining the fabric as a porous medium containing two-phase components, the flow characteristics and temperature field distribution of the opposed jet were obtained using numerical methods. The results indicated that the four different structural types of fabrics exhibited similar heat-moisture transfer characteristics under the air supply mode of the opposed jet. Furthermore, the critical evaporation temperature of fabrics with hygroscopic properties was higher than that of non-hygroscopic fabrics. When the Reynolds number increased from 649.4 to 2165.3 and the excess temperature increased from 40 ℃ to 70 ℃, the drying time was shortened by a maximum of 56.2 % and 25.5 %, respectively. Under the impact of the array opposed jet, the thermal boundary layer on the fabric surface was thinned, and the local Nusselt number presented different peaks along the length direction of the impinging surface. Within the range of operating conditions considered, at a jet wind speed of 4.5 m/s and an excess temperature of 70 ℃, the maximum surface drying rate of the fabric was achieved. The relative deviations of heat flux and mass flux on the impact surface are all within 10 %. This study provides a theoretical basis for the structural design and drying mechanism exploration of fabric drying equipment.
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    • Elsevier

    Thermal-hydrodynamic analysis for internally interrupted-finned tubes: Experimental, numerical and performance study

    Salem O.H.Hegazy A.Yousef K.
    1.1-1.14页
    查看更多>>摘要：© 2024 Elsevier Inc.The characteristics of fluid flow and heat transfer in an internally interrupted-finned tube were studied, experimentally and numerically, and a performance evaluation study was conducted in the present research. The numerical results were validated with the current experimental data as well as other published data, with a maximum deviation of 8.93 %. The effect of different key parameters like fin height, number of fin-rows, fin thickness and number of fins in each row on the thermal-hydrodynamic performance was explored. This study reveals that increasing both fin height and number of fin-rows raises the heat transfer coefficient and friction factor values, but fin thickness negligibly affects the performance. Notably, the average heat transfer coefficient value rises by 25.03 % if the fin height to diameter ratio is increased from 0.1786 to 0.4018, and by 21.4 % if the number of fins is increased from 2 to 6, compared to finless tubes under a mass flow rate of 0.39 kg/s, for three number of fins per row. Compared to the continuously finned tubes, the interrupted-finned tubes have higher heat transfer coefficient values if the interruption length is equal to or less than the fin length, while these values are reduced below that of the continuously finned if the interruption length is larger than the fin length. Clearly, when the interruption length is 3 times the fin length, the heat transfer coefficient value of the continuously finned tube is higher than that of the interrupted-finned one by 3.1 %, while the heat transfer coefficient value of the interrupted-finned tube is higher than that of the continuously finned one by 13.59 %, when the interruption length is reduced to one-third of the fin length. It is recommended using the interrupted-finned tubes over the smooth ones if the amount of mass flow rate flowing through both tubes is the same, but the use of interrupted-finned tubes is not recommended as opposed to smooth ones if both tubes are subjected to the same pressure drop across them.
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    • Elsevier