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Influence of Inclination Angles on Convective Heat Transfer in Solar Panels 倾角对太阳能板对流换热的影响
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410403
Yousuf Alhendal, Sara Touzani
This study presents an experimental and numerical investigation into the thermofluid characteristics of airflow over an inclined, heated plate, mimicking a solar panel. The inclination of the plate was systematically adjusted from 0° to 90°, and the heat flux was varied from 1000 to 4000 W/m², with Reynolds number ranging from 63,000 to 650,000. The study employed a second-order finite volume method for discretization and resolution of steady fluid dynamics problems, with simulations conducted using Ansys Fluent software. The k-ε RNG turbulence model was utilized for these simulations. The numerical results, validated against experimental data, were extrapolated to assess the behaviour at a wide range of attack angles and flow rates. Correlations were established between the average Nusselt number and friction coefficient, as functions of Reynolds number and attack angles. It was observed that heat transfer was optimized at lower attack angles. Conversely, higher inclination angles resulted in increased skin friction, thereby reducing airflow and negatively impacting heat convection. For larger Reynolds numbers, convective flow enhanced and the resistance of the plate was found to be lower at smaller attack angles. These findings have significant implications for the improvement of solar panel efficiency, offering valuable insights into the optimal configuration for maximizing convective heat transfer.
本文对模拟太阳能板的倾斜加热板上气流的热流体特性进行了实验和数值研究。系统调整板倾角为0°~ 90°,热流密度为1000 ~ 4000 W/m²,雷诺数为63000 ~ 650000。采用二阶有限体积法对定常流体动力学问题进行离散和求解,并利用Ansys Fluent软件进行仿真。采用k-ε RNG湍流模型进行模拟。数值结果与实验数据进行了验证,并进行了外推,以评估在大范围攻角和流速下的性能。建立了平均努塞尔数与摩擦系数作为雷诺数和攻角函数的相关关系。在较低的攻角下,传热效果较好。相反,较高的倾角导致表面摩擦增加,从而减少气流,对热对流产生负面影响。雷诺数越大,对流流动增强,迎角越小,板的阻力越小。这些发现对提高太阳能电池板效率具有重要意义,为最大化对流传热的最佳配置提供了有价值的见解。
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引用次数: 1
Evaluating Heat Release Rate in Oenological Fermentation: An Innovative Methodology 评价葡萄酒发酵过程中的热释放率:一种创新的方法
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410402
Matteo Malavasi, Luca Cattani, Alessandro Benelli, Luca Pagliarini, Fabio Bozzoli
The food industry consumes a substantial amount of energy with a large portion dedicated to product heat treatments. Thus, enhancing the efficiency of thermal operations could significantly decrease energy demand, reduce costs, and mitigate pollution in this sector. This is particularly applicable in vinification, where the grape must's temperature is crucial to the final wine quality. In this process, the energy required for fermentative thermostating constitutes a majority of the total energy expenditure. Furthermore, the thermal management of fermenting grape must is influenced by the heat released during the fermentation process. Therefore, understanding the precise distribution of heat release during fermentation could considerably improve the energy efficiency of this production. This study proposes and validates a methodology to achieve this objective. The approach is based on the inverse problem technique, which utilizes temperature measurements of the fermenting product. The validation of this technique shows promising results, indicating the potential applicability of our proposed method.
食品工业消耗了大量的能源,其中很大一部分用于产品热处理。因此,提高热操作的效率可以显著减少能源需求,降低成本,并减轻该部门的污染。这尤其适用于酿酒,葡萄的温度对最终的葡萄酒质量至关重要。在这个过程中,发酵恒温所需的能量占总能量消耗的大部分。此外,发酵葡萄的热管理受发酵过程中释放的热量的影响。因此,了解发酵过程中热量释放的精确分布可以大大提高这种生产的能源效率。本研究提出并验证了一种实现这一目标的方法。该方法是基于反问题技术,利用发酵产物的温度测量。该技术的验证显示了令人满意的结果,表明了我们提出的方法的潜在适用性。
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引用次数: 0
Thermal Performance Optimization of Perforated Fins for Flat Plate Heat Sinks Using CFD Approach 基于CFD方法的平板散热器穿孔翅片热性能优化
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410426
Nizar F.O. Al-Muhsen, Osamah R.S. Al-Khafaji, Firas Basim Ismail
ABSTRACT
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引用次数: 0
A Comprehensive Numerical Analysis of Natural Convection in Nanofluids within Various Enclosure Geometries: A Review 纳米流体中自然对流的综合数值分析:综述
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410420
Sara Mohammed Abbas, Ahmed Kadhim Hussein
ABSTRACT
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引用次数: 0
Comparative Analysis of Longitudinal Vortex Generators and Louvered Fins in Enhancing Thermal Performance in Compact Heat Exchangers 纵向涡发生器与百叶翅片增强紧凑型换热器热性能的对比分析
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410414
Alvaro Valencia, Sebastian Muñoz
Compact heat exchangers equipped with flat tubes have traditionally been employed in automotive cooling systems. To augment thermal performance, louvered fins have been integrated on the air side. over recent decades, the efficacy of longitudinal vortex generators (LVG) in heat exchangers has been rigorously investigated, leading to the proposal of innovative designs characterized by their aerodynamic properties. In this study, a novel LVG design sourced from extant literature was juxtaposed against the conventional louvered fins. The shear-stress transport (SST) k-ω model was utilized to depict the turbulence. When the turbulent flow and heat transfer properties were assessed, distinct variations were observed between multiple rows of LVG and the louvered fins. Enhanced thermal performance, with a value reaching 1.3, was noted for configurations incorporating five rows of LVG arrangements at a Reynolds number of 8000. In contrast, the thermal performance of louvered fins was observed to wane with increasing Reynolds numbers, recording a performance measure of merely 1.08 at the aforementioned Reynolds number.
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引用次数: 0
Investigation of Thermal Conductivity and Wear Resistance in Bio-Inspired Pitted Pistons for Enhanced Performance in Drilling Mud Pumps 提高钻井泥浆泵性能的仿生凹坑活塞的导热性和耐磨性研究
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410422
Xuejing Cheng, Qian Cong
In the demanding environment of drilling mud pumps, failures attributed to piston wear constitute approximately 80% of malfunctioning incidents. While enhanced structural designs and superior materials have been employed, enduring challenges remain. A potential solution identified in previous works is surface texturing, specifically the optimization of pit structures on piston rings, with promising outcomes in friction reduction. Yet, the vital role of thermal parameters in high-intensity environments like mud pumps has been largely overlooked. In this study, the dung beetle's irregular pit structure, known for friction reduction by minimizing soil contact, is utilized as a biological model. The impact of pit geometry, including diameter, angle, and depth, on thermal conductivity, heat transfer, cooling, and heat dissipation has been thoroughly investigated. Preliminary analyses were conducted to gauge the effects of pit diameter on thermal conductivity and piston lifespan. Subsequent analyses were focused on the influence of pit angle in determining thermal gradients across the piston, and its effect on durability. Further investigation was performed to assess the implications of pit depth on heat dissipation and piston longevity. Utilizing Ansys software, the thermal and wear resistance mechanisms of the pitted piston were examined, revealing an enhancement in lifespan by up to 40.60% in comparison to non-pitted counterparts. These findings contribute to the broader comprehension of the interplay between surface texture, thermal performance, and wear resistance, heralding new avenues for thermal management in diverse mechanical machinery. The presented study lays a foundational framework for further research and represents a significant advancement towards a new generation of thermally efficient, wear-resistant mechanical components inspired by nature's perfected mechanisms.
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引用次数: 0
Convective Heat Transfer of Radiating Magneto-Micropolar Nanofluid Flow 辐射磁微极纳米流体流动的对流换热
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410418
Sheetal Gonsalves, Swapna Gabbur
This work presents an in-depth examination of heat and mass transfer phenomena in a radiative and chemically reactive magneto-micropolar nanofluid flow under the influence of convective boundary conditions. The governing equations of the model, represented in their non-linear form via Falkner and Skan transformations, are scrutinized using the Finite Element Method (FEM). Validation with existing literature corroborates the precision of the proposed model. Analyses of the results elucidate the impacts of various parameters on the temperature, species concentration, micro-rotation, and velocity characteristics of the system. Notably, an enhancement in the thermal conductivity of the magneto-micropolar nanofluid is observed in correlation with an increased nanoparticles volume fraction. A positive relationship is discerned between the temperature and the parameters for radiation and convective boundary conditions. Furthermore, a decrement in the Schmidt number is associated with an accelerated diffusion rate. The findings derived from this study hold substantial implications for practical applications in diverse fields such as heat and cooling systems, enhanced oil recovery, thermal management in electronics, material processing, and nanofluidics. This research thus contributes to the existing body of knowledge by offering an intricate understanding of the behavior and manipulation of magneto-micropolar nanofluid flow.
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引用次数: 0
An Examination of Heat Transfer Dynamics in Pulsating Air Flow within Pipes: Implications for Automotive Exhaust Engines 管道内脉动气流的传热动力学研究:对汽车排气发动机的启示
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410404
Yuki Kato, Guanming Guo, Masaya Kamigaki, Kamigaki Fujimoto, Mikimasa Kawaguchi, Keiya Nishida, Masanobu Koutoku, Hitoshi Hongou, Haruna Yanagida, Yoichi Ogata
The detailed understanding of heat transfer in the pulsating airflow in the pipe is critical to reducing heat losses in the engine exhaust stream and improving catalyst performance. In the present investigation, we have scrutinized the impact of pulsation frequencies ranging from 0-90 Hz on the flow velocity field and the consequent heat transfer through a horizontal pipe wall. The Nusselt numbers were evaluated at three distinct cross-sectional points moving from upstream to downstream, by systematically modulating the frequency. Temporal variations in the velocity field and temperature were captured utilizing particle image velocimetry (PIV) and dual-thermocouple probes, respectively. Intriguingly, while the Nusselt number for steady flow at 0 Hz closely adhered to Gnielinski’s equation, the pulsating flow demonstrated a peak between 25-35 Hz, a pattern not predicted by the prevailing quasi-steady-state theory. The observed frequency response of turbulence was found to be congruous with the Nusselt number, indicating that the heightened heat transfer at frequencies of 25-35 Hz could be attributed to the enhanced turbulence and the temperature gradient between the fluid and the wall surface during the deceleration phase in the hysteresis of turbulence in the pulsating flow. The unique frequency characteristics of heat transfer that were uncovered in this study, with respect to both flow velocity and temperature, offer valuable insights for devising strategies to mitigate heat loss during ignition and idling. Furthermore, these findings provide robust benchmarks for validating numerical simulations of pulsating flows in real-life automotive engines.
详细了解管道内脉动气流的传热对减少发动机排气流中的热损失和提高催化剂性能至关重要。在本研究中,我们仔细研究了脉动频率范围为0-90 Hz对水平管壁流速场和由此产生的换热的影响。通过系统地调制频率,在从上游到下游移动的三个不同的横截面点上评估努塞尔数。利用粒子图像测速(PIV)和双热电偶探针分别捕获了速度场和温度的时间变化。有趣的是,虽然0 Hz稳定流的努塞尔数与Gnielinski的方程密切相关,但脉动流在25-35 Hz之间表现出峰值,这是一种未被流行的准稳态理论预测的模式。观测到的湍流频率响应与Nusselt数一致,表明25 ~ 35 Hz频率处的换热加剧可归因于脉动流动中湍流滞回减速阶段湍流增强和流体与壁面之间的温度梯度。在这项研究中发现的关于流速和温度的独特的传热频率特性,为设计减少点火和空转期间热量损失的策略提供了有价值的见解。此外,这些发现为验证实际汽车发动机中脉动流的数值模拟提供了可靠的基准。
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引用次数: 1
Effects of Repeated Heat Treatments on the Wear Resistance of Pre-Carburized Steel 反复热处理对预渗碳钢耐磨性的影响
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410429
Jamal Nayief Sultan, Emad Toma Karash, Mohammad Takey Elias Kassim, Adel M. Ali, Hssein A. Ibrhim
ABSTRACT
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引用次数: 0
Evaluating the Performance and Exhaust Emissions of a Micro Gas Turbine Engine Fueled by Kerosene and Olive Oil Methyl Ester Blends 以煤油和橄榄油甲酯混合物为燃料的微型燃气涡轮发动机性能和废气排放评估
Q4 THERMODYNAMICS Pub Date : 2023-08-31 DOI: 10.18280/ijht.410427
Abdulsattar J. Hasan, Suhad A. Rasheed
The search for renewable, affordable energy alternatives has gained momentum in light of dwindling fossil fuel reserves. Biofuels, particularly those derived from plant sources, present a viable solution to both the energy crisis and environmental degradation. This study focuses on the implementation of olive oil methyl ester (OME) biofuel in micro gas turbine engines. Biofuel blends, with volumetric OME concentrations ranging from 20% to 80% in standard kerosene, were prepared and tested on a GT 85-2-H micro gas turbine unit. The engine's performance and exhaust emissions were evaluated under two different operational parameters: constant speed and constant load. The use of an 80% OME biofuel blend resulted in an 8.7% reduction in overall efficiency and a 13.1% increase in specific fuel consumption (SFC) under an 80% load. However, it also led to a significant improvement in exhaust emissions, with reductions of 28.8%, 39%, and 33.8% recorded for carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO x ), respectively. Similarly, under a constant speed test at 20000 rpm, an 80% OME blend caused a 10.5% reduction in overall efficiency and a 13.6% increase in SFC. Nevertheless, the same blend improved the CO, HC, and NO x emissions by 38%, 41.4%, and 36%, respectively. The findings confirm the potential of OME as a biofuel in micro gas turbine engines, underlining its effectiveness in reducing harmful emissions. This research emphasizes the feasibility of biofuels derived from olive oil in addressing future energy demands while mitigating environmental impact.
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International Journal of Heat and Technology
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