Heat Transfer Performance Research Articles

Investigation on the design and heat transfer performance of dry-grinding heat pipes grinding wheels

Investigation on the design and heat transfer performance of dry-grinding heat pipes grinding wheels

Nitrogen-Doped Graphene Aerogel toward Efficient Solar Steam Generation: Synergistic Effects of Thermal Conductivity and Wettability.

Solar-driven interfacial evaporation technology is regarded as a promising strategy for global freshwater shortage owing to its green and sustainable desalination process. Graphene aerogel (GA) is widely utilized in the design of solar-driven steam generation systems due to its excellent photothermal conversion efficiency and broad spectral absorption. Given the significant impact of hydrophilicity and thermal insulation on the performance of evaporators, nitrogen doping in the graphene structure not only effectively enhances its wettability but also allows for moderate tuning of its thermal conductivity, thereby optimizing the overall performance of the evaporator. Therefore, graphene oxide (GO) and ethylenediamine were used to prepare nitrogen-doped graphene aerogel (NGA) via a one-step hydrothermal method. Experimental investigations and molecular dynamics (MD) simulations were employed to explore the effects of varying nitrogen-doping concentrations on the thermal conductivity and wettability of NGA. The results revealed that as the nitrogen-doping concentration increased, the aerogel exhibited enhanced wettability, while the thermal conductivity initially decreased and then increased. This phenomenon is attributed to the fact that improved wettability can hinder heat convection, resulting in reduced heat transfer efficiency. However, further enhancement in wettability reduces the solid-liquid interfacial thermal resistance, thereby boosting heat transfer performance. Consequently, NGA-2, with an optimal nitrogen-doping concentration, demonstrated superior evaporation performance, achieving a high evaporation rate of 1.64 kg m-2 h-1 and an outstanding evaporation efficiency of 92.2% under one-sun irradiation. This study highlights the improved performance of solar evaporators through the synergistic effects of heat and mass transfer, underscoring their significant potential in seawater desalination applications.

Numerical Investigation of Heat Transfer and Flow Dynamics in Tubes with DNA-Inspired Slotted Inserts

Within the realm of industrial energy conservation, the optimization of heat exchanger performance is paramount for the augmentation of energy utilization efficiency. This investigation employs computational fluid dynamics (CFD) simulations to elucidate the effects of an innovative DNA-Inspired Slotted Insert (DSI) on the convective heat transfer and pressure drop characteristics within heat exchange tubes. The study provides a thorough analysis of fully turbulent flow (Re = 6600−17,200), examining the effects of various DSI pitches, key lengths, and geometries. The findings reveal that the DSI instigates a three-dimensional spiral flow pattern, which is accompanied by an escalation in the Nusselt number (Nu) and friction factor (f) with increasing Reynolds numbers. An inverse relationship between Nu and both pitch and key length is observed; conversely, f exhibits a direct correlation with these parameters. The study identifies an optimal configuration characterized by a pitch of 10 mm and a key length of 1.5 mm, with square keys demonstrating superior heat transfer performance relative to other geometrical configurations. This research contributes significant design and application insights for double-helical inserts, which are pivotal for the enhancement of heat exchanger efficiency.

Performance of heat transfer in Al2O3/MWCNT hybrid nanofluid flow using machine learning models

Abstract This investigation diverges from traditional studies concentrating on single-component nanofluids, instead examining the thermophysical benefits of hybrid nanofluids, like Al₂O₃/MWCNT, aimed at improving thermal conductivity and heat transfer efficiency in passive systems. Machine learning is a promising solution for designing efficient heat exchangers by understanding intricate relationships and utilizing suitable modelling techniques. Numerical simulations were conducted to validate the benchmark results; later, passive techniques were incorporated into the numerical model to predict the heat transfer characteristics. The dataset derived from numerical simulation results is employed to train contemporary machine learning methodologies, including support vector regression (SVR), decision tree (DT), and random forest (RF). Data from experiments and CFD analysis were gathered for preprocessing and machine learning (ML) analysis. The preprocessing phase involved the application of a standard scaler operation to enhance accuracy levels. The models underwent validation using ten experimental data samples to assess their performance against statistical tool metrics. A higher thermal performance factor (ThPF) is observed with the divergent nozzle insert in the plain tube at 0.028 vol% of MWCNT/Al2O3 (HNF3) at Reynolds number 3093. R2 values of SVR, DT and RF are predicted as 0.95, 0.98 and 0.99, respectively, for the case of HNF3 fluid flowing through the divergent nozzle insert. The investigation broadens its conclusions to include improvements in passive heat transfer, encompassing extended surfaces and geometric alterations, offering practical guidance for developing advanced heat exchanger designs.

Numerical Investigations of Superconducting Material Cooling Using Buoyancy-Driven Heat Transport in Cryogenic Nanofluids

This study explores the effect of nanoparticle addition on the overall heat-carrying capacity of base liquid nitrogen in natural convection. Moreover, the work also addresses the nanoparticle sedimentation problem that is prominent in natural convection and proposes subtle modifications in heat source location to avoid sedimentation. For this, a 6 mm superconducting material is immersed in a cooling tub filled with liquid nitrogen. The cooling capacity of cryogenic fluids without boiling is considerably low. Hence, the alumina, silicon oxide, and titania nanoparticles are suspended in the base liquid nitrogen. A computational model, which relies on phase-averaged Eulerian tracking of nanoparticle suspensions, is employed to accurately predict the enhancement in heat transfer characteristics. Furthermore, the study addresses the influence of nanoparticle sedimentation in natural convection and proposes modifications to the cooling domain and superconducting material locations to mitigate sedimentation issues. The findings reveal a remarkable 70% increase in the heat transfer coefficient for 0.5% alumina nanoparticles suspension in the base liquid nitrogen. These results demonstrate the potential for significantly improving heat transfer performance in superconducting systems while minimizing the adverse effects of nanoparticle sedimentation.

Optimization of Heat Transfer Performance in Solar Radiation Collector Tubes with Circular Cross-Section: A Review

The performance of heat transfer in the solar radiation collector tube with a circular cross-section has an important potential for the promotion of solar thermal systems. This review paper discusses the parameters affecting heat transfer in these collector tubes, such as tube geometry, type of material, fluid flow, and environment. The focus of this review is on state-of-the-art methods for improving heat transfer including surface modifications, Nano fluids, and passive heat transfer enhancement strategies. Recent improvements in their material selection, nanotechnology, and new heat transfer fluids are discussed. The review seeks to offer significant references for future innovations and practical applications of those innovations in the field of solar thermal energy systems, and, thereby, provide a concise synthesis of the current state of the art in solar thermal technology. The research outcomes indicate that although considerable advancements have been realized in heat transfer performance optimization, continuous investigation into aspects like energy storage, hybrid configurations, and innovative coatings is essential for further enhancing the efficiency and cost-effectiveness of solar radiation collector tubes. .Key Words: Solar collector, heat transfer optimization, circular cross-section, heat transfer enhancement, nanofluids, thermal performance, solar energy.

Effects of evaporator wettability on the start-up and heat transfer performance of an oscillating heat pipe

Effects of evaporator wettability on the start-up and heat transfer performance of an oscillating heat pipe

Temperature Uniformity Control of 12-Inch Semiconductor Wafer Chuck Using Double-Wall TPMS in Additive Manufacturing.

In semiconductor inspection equipment, a chuck used to hold a wafer is equipped with a cooling or heating system for temperature uniformity across the surface of the wafer. Surface temperature uniformity is important for increasing semiconductor inspection speed. Triply periodic minimal surfaces (TPMSs) are proposed to enhance temperature uniformity. TPMSs are a topic of increasing research in the field of additive manufacturing and are a type of metamaterial inspired by nature. TPMSs are periodic surfaces with no intersections. Their continuous curve offers self-support during the additive manufacturing process. This structure enables the division of a single space into two domains. As a result, the heat transfer area per unit volume is larger than that of general lattice structures, leading to a superior heat transfer performance. This paper proposes a new structure called a double-wall TPMS. The process of creating a double-walled TPMS by adjusting the thickness of the sheet TPMS was investigated, and its thermal performance was studied. Finally, a double-wall TPMS was applied to the chuck. The optimal designs for the diamond and gyroid structures exhibited a difference in surface temperature uniformity of 0.23 °C and 0.66 °C, respectively. Accordingly, the models optimized with the double-wall TPMS are proposed.

Molecular dynamics study on boiling characteristics of liquid sodium under different wall temperature: Incipient boiling superheat, heat transfer performance and mechanism

Molecular dynamics study on boiling characteristics of liquid sodium under different wall temperature: Incipient boiling superheat, heat transfer performance and mechanism

Thermo-hydraulic performance inside convergent rectangle channel with large-deformed dimples

The cooling technology of convergent rectangle channel is widely applied in heat exchangers, electronic devices and aerospace, especially in the field of turbine blade internal cooling.A numerical study was conducted to research the thermo-hydraulic performance inside a convergent rectangle channel with large-deformed dimples. The heat transfer and flow characteristics were presented to demonstrate the heat transfer enhancement mechanism. The effect of dimple configuration, dimple depth, and dimple radius on thermo-hydraulic performance were discussed at Reynolds numbers ranging from 15,000 to 65,000. The numerical results revealed that the large-deformed dimple structure disrupts the boundary layer flow, resulting in better mixing between the boundary layer flow and the core fluid. The dimple configuration of diminishing dimples showed better heat transfer performance and lower pressure loss. The Nusselt number ratio, friction factor ratio, and performance evaluation criteria (PEC) increase with rising dimple depth and dimple radius. Within the scope of the present work, the maximum PEC was 1.62 when the dimple configuration was diminishing, the dimple depth was 5mm, and the dimple radius was 10mm.

EXPERIMENTAL STUDY OF FULLY DEVELOPED TURBULENT FLOW IN INTERNALLY FINNED TUBES

A steady, hydrodynamically and thermally fully developed turbulent water flow in internally finned tubes with constant-heat-flux boundary condition is investigated experimentally. In this experiment, 70°C hot water passes the inner tube while 20°C cold water flows through the annulus passage. In order to eliminate thermal contact resistance, the circular tube having a length of 1400 mm with inner fins is directly milled from a cylinder. Apart from a smooth tube, three internal-finned-tube heat exchangers having 4, 6, and 8 longitudinal trapezoidal fins are tested. For Re = 5000, the tested tubes with 4, 6, and 8 fins can improve thermal performance by approximately 35.4, 44.6, and 67.2%, respectively, but merely increase friction factor by 1.92, 4.8, and 6.73%, respectively, compared to a smooth tube. The increases with respect to to a smooth tube in both Nu and <i>f</i> become smaller at a higher Re for <i>N</i> = 4, 6, and 8. As pressure drop, increases, the <i>Q</i> of the tested finned tubes first grows rapidly, and this growth curve gradually becomes flatter at a higher Δ<i>P</i>. Consequently, the heat-transfer performance will become worse as Δ<i>P</i> > 3.5 kPa for the proposed heat exchangers. Additionally, the performance evaluation criterion (PEC) is proposed to assess the performances of the proposed internally finned tubes. It is shown that the heat exchanger with 8 fins has the best thermo-hydraulic performance. Finally, correlating equations for Nu and f with respect to Re are presented for a range of 3000 ≤ Re ≤ 7250 and <i>N</i> = 0, 4, 6, and 8.

A numerical heat transfer model and performance evaluation of coaxial geothermal heat exchanger under soil freezing conditions

A numerical heat transfer model and performance evaluation of coaxial geothermal heat exchanger under soil freezing conditions

An investigation on convective regasification heat transfer performance of supercritical methane inside horizontal heated circular tubes

An investigation on convective regasification heat transfer performance of supercritical methane inside horizontal heated circular tubes

Study on heat transfer performance of aircraft brake using CFD simulation

Study on heat transfer performance of aircraft brake using CFD simulation

Copper fiber wick with scaly fins fabricated by multi-tooth cutting for directional heat transfer

Wicks with directional liquid transport properties are the decisive factor in fabricating high-performance directional heat transfer devices. Aiming at the lack of wicks that can maintain directional liquid transport performance after high-temperature processes, sintered copper fiber wicks (SCFWs) with scaly fins were prepared. The copper fibers with scaly fins were fabricated by multi-tooth cutting and the additional driving force of scaly fins on ethanol was used to achieve directional capillary flow. The effects of scaly fin direction, sintering parameters, and porosity on the capillary performance of SCFWs were studied. The results show that the direction of scaly fins can adjust the liquid flow direction. The capillary performance parameter of SCFW3, with the same fin direction as the flow direction of ethanol, is 65.5% higher than that of SCFW1 with the opposite fin direction. Sintering temperature and holding time affect the formation of sintered necks and micropores, which affects the capillary performances of SCFWs. The effects of sintered necks on the capillary performances of SCFWs are more obvious than micropores on copper fibers. In addition, the relatively low porosity in the range of 70–80% helps improve the capillary performance of SCFWs. The SCFWs provide a feasible method for the fabrication of phase change heat transfer devices with directional heat transfer performances.

Heat transfer performance of ultra-thin vapor chambers with composite wick for electronic thermal management

Heat transfer performance of ultra-thin vapor chambers with composite wick for electronic thermal management

Experimental study on the heat transfer performance of heat pipe radiators with Diverse structural configurations for laser pump sources

Experimental study on the heat transfer performance of heat pipe radiators with Diverse structural configurations for laser pump sources

Digital strategies to improve the product quality and production efficiency of fluorinated polymers: 2. Heat removal performance of reactor with internal and external cooling systems

A reactor's heat transfer efficiency can be significantly enhanced and the fluid temperature uniformity can be controlled through introducing cooling water in the agitator and regulating the flow ratio of cooling water in the agitator and jacket.

Dynamic heat transfer mechanisms of internal thermal mass: effects of thermal conductivity and diffusivity under varied temperature conditions

The appropriate use of internal thermal mass in buildings can reduce energy consumption while maintaining thermal comfort. A prerequisite for selecting suitable internal thermal mass is to establish its relationship with indoor air temperature and heat exchange. However, there is currently a lack of analytical models to describe this relationship. This study investigates the dynamic heat transfer performance of internal thermal mass under constant indoor air temperature, exponentially declining temperatures, and sinusoidal heating and cooling conditions. The results show that under constant indoor air temperature, materials with lower thermal conductivity (e.g., plywood with 0.17 W/m·°C) generate more thermal waves and experience faster surface temperature rises compared to materials with higher conductivity (e.g., reinforced concrete with 1.74 W/m·°C). In the case of exponentially declining indoor air temperature, heat exchange per unit area decreases with increasing thickness, with plywood (0.02 m) reaching its peak temperature at 6360 s, and reinforced concrete (0.2 m) at 9900 s. For sinusoidal temperature variations, the decrement factor for plywood and reinforced concrete decreases from 0.90 to 0.59 as thickness increases from 0.02 m to 0.06 m, while the time lag increases from 1.45 hours to 3.16 hours. The heat exchange is primarily related to the effective thermal capacity per unit area and the storage coefficient, which are determined by the physical properties of the internal thermal mass. These findings provide a quantitative basis for estimating the impact of internal thermal mass on indoor air temperature and heat exchange in the early stages of building design.

Free convection investigation for a Casson-based Cu-H 2 O nanofluid in semi parabolic enclosure with corrugated cylinder.

The optimization of heat transfer in various engineering applications, such as thermal management systems and energy storage devices, remains a crucial challenge. This study aims to investigate the potential of Casson-based Cu-H2O nanofluids in enhancing free convection heat transfer within complex geometries. The research examines the free convection heat transfer and fluid flow characteristics of a Casson-based Cu-H2O nanofluid within a semi-parabolic enclosure that includes a wavy corrugated cylinder. Utilizing numerical simulations based on the Galerkin Finite Element Method, the study investigates the impact of different factors, including the Rayleigh number (103≤Ra ≤ 106), Casson fluid parameter (0.1≤γ≤1), corrugation number (3≤N≤10), nanoparticle volume fraction (0≤ϕ≤0.15), and enclosure inclination angle (0°≤ζ≤60°), on both heat transfer efficiency and flow patterns. The results reveal that increasing the Rayleigh number and Casson fluid parameter enhances heat transfer performance, with the average Nusselt number increasing by up to 165% as Ra increases from 103 to 106. An optimal range of corrugation numbers is identified for maximizing heat transfer at higher Rayleigh numbers. The addition of nanoparticles significantly improves heat transfer, with a 20% increase in the average Nusselt number observed at Ra=105 when the nanoparticle volume fraction increases from 0 to 0.15. These findings provide valuable insights for designing more efficient thermal management systems in applications such as electronics cooling, solar thermal collectors, and heat exchangers, potentially leading to improved energy efficiency and performance in various industrial and technological sectors.