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heat transfer enhancement and Vortex Flow Structure in the Spirally Fluted Tubes

Journal of Thermal Science 2021年第5期30卷 1814-1826页

作者： WANG Xingtian YUCHI Wensi ZHU Junfeng YAO Jianan CAO Liang State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing 100038China Institute of Water Resources for Pastoral Area Ministry of Water Resources of the People's Republic of ChinaHuhhot 010020China

The turbulence kinetic energy and heat transfer performance of air in spirally fluted tube were numerically studied at a constant wall temperature with Reynolds number(Re)between 5000 and ***,the flow dynamics and heat transfer performance of spirally fluted tubes with five different geometric parameters as well as the effects of separation vortex and swirling wake flow on heat transfer and flow resistance were *** to the results,heat transfer is enhanced mainly because the fluid hit the windward side of the flute,thus generating a strong turbulence kinetic energy to further reconstruct the boundary *** second reason is that the formation of the recirculation zone between the flutes disturbs the boundary layer caused by the flow *** the increase of flute depth ratio(L_(d)/D),the separation vortex will become stronger and larger on the leeward side of *** separation vortex will break the boundary layer and improve the heat transfer capacity which is accompanied with the increase of fluid *** the flute pitch length ratio(L_(p)/D)decreases,the spiral flow is strengthened,and meanwhile more wake flow is *** spiral flow causes little impact on enhancing heat transfer but inhibits the development of the separation vortex and fluid pulsation;in addition,the fluid resistance is reduced at the same *** maximum value of the average Nusselt number appears when Re=5000,L_(d)/D=0.25 and L_(p)/D=1.00,which is 2.53 times the value of smooth *** view of the whole range of Reynolds number,the thermal performance enhancement factor indicates that L_(d)/D=0.15 and L_(p)/D=1.00 are the optimal geometric design parameters.

关键词： heat transfer enhancement vortex flow resistance spirally fluted tube heat exchanger flue gas heat recovery

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heat transfer enhancement with Mixing Vane Spacers Using the Field Synergy Principle

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Chinese Journal of Mechanical Engineering 2017年第1期30卷 127-134页

作者： YANG Lixin ZHOU Mengjun TIAN Zihao School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing Key Laboratory of Flow and heat transfer of Phase Changing in Micro and Small Scale Beijing Jiaotong UniversityBeijing 100044China

The single-phase heat transfer characteristics in a PWR fuel assembly are important. Many investigations attempt to obtain the heat transfer characteristics by studying the flow features in a 5 x 5 rod bundle with a spacer grid. The field synergy principle is used to discuss the mechanism of heat transfer enhancement using mixing vanes according to computational fluid dynamics results, including a spacer grid without mixing vanes, one with a split mixing vane, and one with a separate mixing vane. The results show that the field synergy principle is feasible to explain the mechanism of heat transfer enhancement in a fuel assembly. The enhancement in subchannels is more effective than on the rod＇s surface. If the pressure loss is ignored, the performance of the split mixing vane is superior to the separate mixing vane based on the enhanced heat transfer. Increasing the blending angle of the split mixing vane improves heat transfer enhancement, the maximum of which is 7.1%. Increasing the blending angle of the separate mixing vane did not significantly enhance heat transfer in the rod btmdle, and even prevented heat transfer at a blending angle of 50%. This fmding testifies to the feasibility of predicting heat transfer in a rod bundle with a spacer grid by field synergy, and upon comparison with analyzed flow features only, the field synergy method may provide more accurate guidance for optimizing the use of mixing vanes.

关键词： rod bundle mixing vane heat transfer enhancement field synergy

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heat transfer enhancement of an Automobile Engine Radiator using ZnO Water Base Nanofluids

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Journal of Thermal Science 2020年第4期29卷 1010-1024页

作者： Muhammad QASIM Muhammad SAJID KAMRAN Muhammad AMMAR Muhammad ALI JAMAL Muhammad YASAR JAVAID Department of Mechanical Engineering University of Engineering and TechnologyLahore 54890Pakistan Department of Chemical Engineering Technology Government College UniversityFaisalabad 38000Pakistan Department of Mechanical Engineering Technology Government College UniversityFaisalabad 38000Pakistan

In this research paper, the forced convective heat transfer enhancement of a Suzuki Mehran(VXR) 2016 radiator(heat exchanger) along with pressure drop and friction factor by utilizing Zinc oxide(Zn O) water based nanofluids has been experimentally studied. Three types of nanofluids with different volumetric concentrations of Zn O nanoparticles(0–0.3%) were employed in order to understand its effect on heat transfer enhancement. The experimental setup was completely designed as closely as possible to the car cooling system. The experimentation has been done under laminar flow conditions(186≤Re≤1127) at different fluid volume flow rates(2–12 L/min) and constant fluid inlet temperature(70°C) to the automobile radiator. A maximum enhancement in heat transfer rate, overall heat transfer coefficient and Nusselt number was obtained up to 41%, 50% and 31% by using nanofluid with 0.2% volumetric concentration of nanoparticles respectively. On the other hand, the mean enhancement in pressure drop and friction factor was obtained up to 47% and 46% by using nanofluid with the same volumetric concentration of nanoparticles i.e. 0.2% respectively. The experimental results also revealed that the heat transfer rate, overall heat transfer coefficient and Nusselt number of nanofluids increases by increasing the volume flow rates and volumetric concentration of nanoparticles. However, these thermal performance parameters of nanofluids started to decline when the volumetric concentration of nanoparticles was increased from 0.2% to 0.3%. Furthermore, pressure drop and friction factor of nanofluids increase by increasing the volumetric concentration of nanoparticles, while pressure drop increases and friction factor decreases by increasing the volume flow rate of nanofluids respectively. At the end, the thermal efficiency of automobile radiator with high cooling rates was obtained by using nanofluid with 0.2% volumetric concentration of nanoparticles.

关键词： ZnO nanoparticles heat transfer enhancement thermal efficiency automobile radiator

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heat transfer enhancement Due to Marangoni Flow Around Moving Bubbles During Nucleate Boiling

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Tsinghua Science and Technology 2006年第5期11卷 523-532页

作者：柯道友王浩彭晓峰 Department of Thermal Engineering Tsinghua University

Nucleate boiling is a very efficient method for generating high heat transfer rates from solid surfaces; however, the fundamental physical mechanisms governing nucleate boiling heat transfer are not well understood. The heat transfer mechanisms around stationary and moving bubbles on very thin microwires were analyzed numerically to evaluate the effect of the bubble motion on the heat transfer from the wire surface. The numerical analysis accurately models the experimentally observed bubble movement and fluid velocities. The analytical model includes the effects of the Marangoni flow around the bubble and the evaporation and condensation within the bubble. The analysis shows that the heat transfer was significantly enhanced by the Marangoni flow around the outside of the bubble which transfers at least twice as much en- ergy from the wire as the heat transfer directly from the wire to the bubble. The enhanced heat transfer due to the Marangoni flow was evident for both stationary and moving bubbles. The moving bubbles also created a wake that further enhanced the heat transfer from the wire. Since the Marangoni number for water is greater than for ethanol for the same conditions, the Marangoni flow and, hence, the bubble velocities are predicted to be greater in water than in ethanol.

关键词： nucleate boiling Marangoni flow vapor bubbles heat transfer enhancement

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Numerical analysis of heat transfer enhancement on steam condensation in the presence of air outside the tube

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Nuclear Science and Techniques 2022年第8期33卷 55-68页

作者： Wen-Tao Li Xian-Ke Meng Hao-Zhi Bian Ming Ding Heilongjiang Provincial Key Laboratory of Nuclear Power System and Equipment Harbin Engineering UniversityHarbin 150001China China Nuclear Engineering Consulting Co. Ltd.Beijing 100073China

In loss-of-coolant accidents,a passive containment heat removal system protects the integrity of the containment by condensing *** a large amount of air exists in the containment,the steam condensation heat transfer can be significantly *** on previous research,traditional methods for enhancing pure steam condensation may not be applicable to steam–air *** the present study,new methods of enhancing condensation heat transfer were adopted and several potentially enhanced heat transfer tubes,including corrugated tubes,spiral fin tubes,and ring fin tubes were ***-CCM+was used to determine the effect of enhanced heat transfer tubes on the steam condensation heat *** to the calculations,the gas pressure ranged from 0.2 to 1.6 MPa,and air mass fraction ranged from 0.1 to *** effective perturbation of the high-concentration air layer was identified as the key factor for enhancing steam–air condensation heat ***,the designed corrugated tube performed well at atmospheric pressure,with a maximum enhancement of 27.4%,and performed poorly at high *** the design of spiral fin tubes,special attention should be paid to the locations that may accumulate high-concentration ***,the ring-fin tubes generally displayed good performance under all conditions of interest,with a maximum enhancement of 24.2%.

关键词： Air–steam condensation Numerical simulation heat transfer enhancement Fin tube

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A Review of heat transfer enhancement through Flow Disruption in a Microchannel

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Journal of Thermal Science 2015年第3期24卷 203-214页

作者： Anupam Dewan Pankaj Srivastava Department of Applied Mechanics Indian Institute of Technology Delhi Hauz Khas New Delhi - 110016 India Instruments R & D Establishment Defence R & D Organisation Dehradun (UK) - 248008 India

In this paper a comprehensive review of heat transfer enhancement through microchannels has been presented. Over the past few years due to multifunetion, shrinking package size and high power dissipation, the heat flux per unit area has increased significantly. Microchannels, with their large heat transfer surface to volume ratio and their small volumes, have shown a good thermal performance. Microchannels have been proven to be a high per- formaace cooling technique which is able to dissipate heat flux effectively from localized hot spots over small surface area. A good amount of heat transfer augmentation techniques have been reported on flow disruption through microchannel. These techniques promote free stream separation at the leading edge which results in boundary layer development and enhanced mixing leading to increased heat transfer. Flow disruption can be achieved through passive surface modifications, such as, shape of channel, dimple surfaces, ribs, cavities, groove structures, porous medium, etc. Combined effects of these geometrical configurations in heat transfer augmenta- tion are also reported in the literature. In this paper recent developments in experimental and numerical simula- tions of single-phase liquid cooled microchannel have been discussed to analyze the pressure drop, friction and heat transfer characteristics due to different flow conditions, roughness structure and passive surface modifica- tions. It has been observed that the flow disruption techniques are effective for heat transfer enhancement with lower penalties of increased pressure drop. The review concludes with suggestions for future research in this area.

关键词： Microchannel heat transfer enhancement boundary-layer pressure drop dimple surface cavitiesand ribs

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Numerical insight into heat transfer enhancement by granules inner-migration in a moving bed:A performance comparison between slanted-stick and plow-shaped agitator

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Particuology 2024年第6期89卷 109-116页

作者： Binfan Jiang Hao Pei Dehong Xia Haiyang Wang School of Energy and Environmental Engineering University of Science and Technology BeijingBeijing 100083China Shunde Graduate School of University of Science and Technology Beijing Guangdong 528399China Jianlong Group&USTB Joint Laboratory Beijing 100083China

Waste heat recovery of high-temperature granules is one of the most promising sustainable energy supply and carbon reduction ways for industry.A moving bed indirect heat exchanger(MBIHE)with inner-migration was proposed for granular heat *** migration and the enhanced heat transfer induced by two types of agitators(i.e.,agitator with slanted stick A_(s)and with plow-shaped surface A_(p))in the MBIHE are analyzed based on DEM coupled with *** to the effective agitation,the average heat transfer coefficient in the granule side is enhanced to∼3 times compared to that without *** heat recovery efficiency in the moving bed reached more than 70%with the agitations of either A_(s)or A_(p).The heat efficiency of A_(s)is∼7%higher than that of A_(p),but with at least 60%greater rotational *** ensure reliable agitation,the A_(p)is suggested to be adopted in the MBIHE to induce granule migration.

关键词： Waste heat recovery High-temperature granule Granule migration heat transfer enhancement Industry energy saving

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heat transfer enhancement of finned shell and tube heat exchanger using Fe_(2)O_(3)/water nanofluid

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Journal of Central South University 2021年第11期28卷 3297-3309页

作者： AFSHARI Faraz SÖZEN Adnan KHANLARI Ataollah TUNCER Azim Doğuş Department of Mechanical Engineering Erzurum Technical UniversityErzurumTurkey Department of Energy Systems Engineering Gazi UniversityAnkaraTurkey Department of Mechanical Engineering Faculty of EngineeringTarsus UniversityMersinTurkey Department of Energy Systems Engineering Burdur Mehmet Akif Ersoy UniversityBurdurTurkey Natural and Applied Science Institute Gazi UniversityAnkaraTurkey

heat transfer mechanisms and their thermal performances need to be comprehensively studied in order to optimize efficiency and minimize energy *** nanoparticles in the base fluid are investigated to upgrade the thermal performance of heat *** this numerical study,a finned shell and tube heat exchanger has been designed and different volume concentrations of nanofluid were tested to determine the effect of utilizing nanofluid on heat ***_(2)O_(3)/water nanofluids with volume concentration of 1%,1.5% and 2% were utilized as heat transfer fluid in the heat exchanger and the obtained results were compared with pure *** Fluent software as a CFD method was employed in order to simulate the mentioned *** simulation results indicated the successful utilization of nanofluid in the heat ***,increasing the ratio of Fe_(2)O_(3) nanoparticles caused more increment in thermal energy without important pressure ***,it was revealed that the highest heat transfer rate enhancement of 19.1% can be obtained by using nanofluid Fe_(2)O_(3)/water with volume fraction of 2%.

关键词： heat transfer enhancement nanofluid shell and tube heat exchanger Fe_(2)O_(3)

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The regulation mechanism and heat transfer enhancement of composite mixed paraffin and copper foam phase change materials

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Science China(Technological Sciences) 2023年第8期66卷 2346-2360页

作者： YANG HanXue ZHANG GuanHua DOU BinLin CUI GuoMin YAN XiaoYu LU Wei WANG ZiLong School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai 200093China Environment and Sustainability Institute University of ExeterPenrynCornwall TR109FEUK

Phase change materials(PCMs)have remarkable energy storage capacity and promising applications in the field of thermal control of electronic *** problem of thermal property improvement and heat transfer of PCMs in metal-foam heatsinks is an important task for thermal management of electronic *** paraffin samples were prepared by mixing appropriate proportions of paraffin(mass)at various *** scanning calorimetry analysis revealed that the maximum enthalpy of 206.3 J/g is obtained by mixing 20%of 17°C liquid paraffin and 80%of 29℃ solid *** and cooling cycling tests revealed that mixed paraffin exhibits excellent thermal stability and that the regulation method marginally affects thermal ***,composites were prepared by embedding PCM into a copper foam by melt *** thermal conductivity of the composites increased to 4.35 W/(m K),corresponding to 20 times its original *** addition,density functional theory and experimental results were in good agreement,indicating that the regulation method is practical and effective.

关键词： phase change materials regulation mechanism temperature dependence thermal conductivity heat transfer enhancement

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Experimental study on heat transfer enhancement of square-array jet impingement by using an integrated synthetic jet actuator

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Science China(Technological Sciences) 2023年第12期66卷 3439-3449页

作者： TAN JunWen LYU YuanWei ZHANG JingZhou ZHANG JingYang College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China College of Astronautics Nanjing University of Aeronautics and AstronauticsNanjing 210016China

A novel concept is proposed in the present study for improving the square-array jet impingement heat transfer by integrating a synthetic jet actuator into the array *** illustrate the potential of this concept,an experimental investigation is performed,wherein two jet Reynolds numbers(Re=3000 and 5000),three hole-to-hole pitches(X/d=Y/d=4,5 and 6),and three impinging distances(H/d=2,6 and 10)are considered while the synthetic jet is actuated at a fixed frequency of 180 Hz with a characteristic Reynolds number(Re_(0))of about *** results show that the synthetic jet has rare influence on the stagnation heat transfer of square-array jet but effectively improves the local heat transfer at the central zone of array *** potential is tightly dependent on the array layout,Reynolds number and impinging *** general,the spatially-averaged Nusselt number augment behaves more significantly for the situations with smaller jet Reynolds number and bigger impinging distance.

关键词： jet impingement heat transfer enhancement square-array jet synthetic jet actuator

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