How can particle heat transfer be enhanced?
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Particle heat transfer can be significantly enhanced through various innovative methods and materials, as evidenced by recent research. One effective approach is the use of nanofluids, which are fluids containing nanoparticles that improve thermal conductivity and heat transfer rates. For instance, water-based Al2O3-MWCNT hybrid nanofluids have shown to enhance heat transfer efficiency in tube/shell heat exchangers, with diamond-shaped tubes offering superior performance due to optimal geometric configurations . Similarly, the incorporation of nanoparticles such as titanium dioxide, copper oxide, and aluminium oxide into a Newtonian medium has been found to remarkably enhance thermal performance, with copper oxide nanoparticles being the most effective thermal enhancers . Experimental investigations have also demonstrated that the addition of nanoparticles like Aluminium Oxide (Al2O3) and Copper (II) oxide (CuO) to compact heat exchangers can significantly increase the heat transfer rate, especially at higher concentrations and heat fluxes . Moreover, oil-based nanofluids have been identified as having a high heat carrying capacity, which substantially increases the heat transfer rate in various heat exchanger applications . The geometry of the heat transfer surface plays a crucial role as well. Corrugated plate-fin heat sinks, for example, create higher disturbances in the flow, leading to enhanced heat transfer . The particle-resolved method, which incorporates the thermophysical properties of both the base fluid and nanoparticles, has shown that nanoparticles near the wall increase local heat flux, thereby enhancing heat transfer . Passive heat transfer enhancement methods, such as the use of inserts, rough surfaces, and extended surfaces, have also proven to be cost-effective and reliable for improving thermal performance without the need for external power . Additionally, gold-silica core-shell nanoparticles have been shown to enable faster heat transfers to liquid water due to direct interfacial coupling between metal electrons and silica phonons, optimizing thermoplasmonic applications . The shape of nanoparticles, such as platelets, has been found to significantly influence the rate of heat transfer enhancement, with certain shapes leading to higher temperature nanofluids . Lastly, the use of nanofluids consisting of water and metal oxides like CuO and ZnO in shell and tube heat exchangers has resulted in higher overall and convective heat transfer coefficients compared to base fluids . These findings collectively highlight the multifaceted approaches to enhancing particle heat transfer, encompassing material composition, fluid properties, and system geometry.
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| Papers (10) | Insight |
|---|---|
2 Citations | Particle heat transfer can be enhanced through passive techniques like using nanofluids, which are cost-effective and reliable, requiring no extra power for improved thermal efficiency compared to active methods. |
| Particle heat transfer can be enhanced by adding nanoparticles to the heat transfer fluid, increasing thermal conductivity, and improving heat transfer rate in compact heat exchangers. | |
| Particle heat transfer can be enhanced by utilizing gold-silica core-shell nanoparticles due to direct interfacial coupling between metal electrons and silica phonons, leading to faster heat transfers. | |
| Particle heat transfer can be enhanced by using oil-based nanofluids in heat exchangers, where factors like nanoparticle type, concentration, and base fluid selection play crucial roles in improving heat transfer rates. | |
| Corrugated plate-fin heat sinks can enhance particle heat transfer by creating disturbances that increase localized heat transfer coefficients, leading to improved heat dissipation efficiency. | |
| Particle heat transfer can be enhanced by using nanofluids, which are colloidal mixtures of nano-sized particles in a base fluid. This enhances heat transfer characteristics, improving overall heat transfer coefficients. | |
30 Citations | Particle heat transfer can be enhanced by utilizing different shapes of Cu nanoparticles in water-based nanofluids, impacting skin friction, Nusselt number, and heat transfer rates significantly. |
| Particle heat transfer can be enhanced by dispersing copper oxide nanoparticles in a Newtonian medium, as they are found to be the most effective thermal enhancers among titanium dioxide and aluminium oxide. | |
| Particle heat transfer can be enhanced by using Al2O3-MWCNT hybrid nanofluid in tube/shell heat exchangers, with diamond-shaped tubes showing superior heat transfer efficiency and up to 103.07% enhancement. | |
| Particle heat transfer can be enhanced by nanoparticles near the wall increasing local heat flux under constant wall temperature and decreasing local wall temperature under constant heat flux conditions. |
Related Questions
How heat transfer in tube bundles moving packed bed of particles is improved?10 answersImproving heat transfer in tube bundles within a moving packed bed of particles involves several innovative strategies, as evidenced by recent research. One approach is the use of finned tubes, although it's noted that while these can prevent more active particle behavior, leading to a lower average heat transfer coefficient compared to bare tubes, the design and immersion depth in the bed are critical factors for optimization. The introduction of internal heat fins in slender packed beds has been shown to significantly enhance radial heat transport near the reactor wall, improving thermal performance by increasing the conductive portion of heat transfer.
The incorporation of built-in elements such as deflection surfaces, windows, and directing sections in tube-bundle heat exchangers can also lead to constant mixing in the product flow, thereby preventing maldistribution and axial backmixing, which in turn improves heat transfer. Computational fluid dynamics (CFD) simulations, particularly when adjusted for local phenomena like contact points between particles, have been instrumental in understanding and enhancing heat transfer in packed beds.
Numerical simulations suggest that optimizing particle size distribution within the bed can significantly improve heat transfer performance by optimizing velocity and temperature fields, thereby reducing equivalent thermal resistance. Studies on elliptic tube heat exchangers have shown that the configuration of tube bundles (inline vs. staggered) and the fluidization number can greatly affect the heat transfer coefficient and Nusselt number, indicating the importance of geometric and operational parameters.
Innovations in packed bed heat storage devices, which aim for uniform distribution of heat transfer fluid over the solid heat storage medium, highlight the importance of flow distribution and heat exchange uniformity for enhanced heat storage efficiency. The creation of high thermal conductive bridges between particles in a packed bed has been found to significantly increase effective thermal conductivity without substantially affecting gas permeability, indicating a promising method for heat transfer enhancement.
Experimental studies on dense granular flows in vertical channels for moving packed-bed heat exchangers have identified optimal conditions for achieving uniform particle flow distribution, which is crucial for efficient heat transfer in such systems. Lastly, the design of tube bundle heat exchangers with helically extended heat exchange tube rows arranged in a staggered manner in an annular cavity can also contribute to strong heat exchange capacity by ensuring that the external heat exchange medium flows in a consistent direction, reducing flow energy loss.
These findings collectively underscore the multifaceted approaches to enhancing heat transfer in tube bundles within moving packed beds of particles, ranging from structural modifications and flow optimization to thermal conductivity improvements.
How can particle packed bed heat transfer be enhanced?10 answersEnhancing heat transfer in particle packed beds is a multifaceted challenge that can be addressed through various innovative strategies, as evidenced by recent research. One effective approach involves the use of directional granule migration, induced by an optimized agitator with a plow-shaped surface, which significantly enhances the heat transfer coefficient by 383% in a 3-D shell heat exchanger designed to match the 3-D migration of granules. Similarly, the application of dimpled structures to particles in structured packed beds has been shown to increase the Nusselt number by up to 57.73%, thereby improving the comprehensive heat transfer coefficient by up to 47.29%.
The uniformity of granular flow in vertical packed beds also plays a crucial role in improving heat transfer efficiency. By optimizing granular flow uniformity, the efficient inter-phase heat transfer can be significantly enhanced. Additionally, particle-resolved computational fluid dynamics (PRCFD) and the local caps method for modifying packed bed geometry have been utilized to ensure high-quality mesh around contacts, which is essential for accurate simulation of heat transfer.
Internal heat fins have been identified as a method to increase conductive radial heat transport near the reactor wall in slender packed beds, leading to an increase in thermal performance. The local bridges method, another innovative approach, modifies contact points in packed beds to improve heat transfer, with a suggested correction reducing simulation error for bed surface temperature by 75%.
Empirical correlations developed for small cylinders within porous media subject to forced convection heat transfer offer a method for accurately predicting the Nusselt number, enhancing the understanding of heat transfer in such systems. Numerical simulations have shown that radial distribution of multi-particle size can optimize velocity and temperature fields, thereby improving heat transfer performance. Lastly, modeling the Effective Thermal Conductivity (ETC) of pebble beds in nuclear reactors by considering convection and radiation alongside conduction has been highlighted as fundamental for enhancing heat transfer.
What are the fundamental mechanism of heat transfer in particles?5 answersThe fundamental mechanisms of heat transfer in particles involve various factors such as particle heat transfer, dispersed phase heat transfer, radiation heat transfer, liquid interfacial layering, agglomeration, Brownian motion, electron-phonon coupling, and heat transfer to the particle environment. These mechanisms play crucial roles in enhancing the effective thermal conductivity and understanding heat transfer phenomena in different systems. For instance, in nanofluids, the complex heat transfer mechanisms involving nanoparticle diffusivity, thermophoretic effects, and enhanced Brownian motion contribute to abnormal heat transfer augmentation. Similarly, in ultrafast laser-pulsed excitation of metal nanoparticles, nonlocal and nonequilibrium heat conduction near the core nanoparticle affects the overall heat transfer rate and temperature dynamics. Understanding these mechanisms is essential for optimizing heat transfer processes and designing efficient thermal systems.
How nanofluids enhance heat transfer in shell and tube heat exchanger?5 answersNanofluids enhance heat transfer in shell and tube heat exchangers by improving the thermal conductivity of the working fluid. The addition of nanoparticles, such as Al2O3 and Cu, to the base fluid increases the heat transfer rate compared to the base fluid alone. The heat transfer enhancement is more significant at higher concentrations of nanoparticles and heat fluxes. The use of nanofluids in heat exchangers can significantly improve their performance, making them more efficient and compact for a wide range of industrial applications. The Nusselt number, which represents the heat transfer rate, increases with the increase in nanofluid volume concentrations and mass flow rates. The friction factor, which represents the resistance to flow, can also be reduced by using nanofluids. Overall, the use of nanofluids in shell and tube heat exchangers enhances heat transfer and improves their thermal performance.
What techniques have been developed to enhance the heat transfer performance of systems that prioritize thermal management?3 answersPassive heat transfer enhancement techniques have been developed to improve the thermal performance of systems prioritizing thermal management. These techniques include the use of inserts (twisted tapes, conical strips, baffles, winglets), extended surfaces (fins), porous materials, coil/helical/spiral tubes, rough surfaces (corrugated/ribbed surfaces), and nanofluids (mono and hybrid nanofluid). Another approach is the use of thermal conductivity enhancers (TCEs) such as fins, foams, and nanoparticles to overcome the poor thermal conductivity of phase-change materials (PCMs) used in heat sinks. Additionally, heat transfer enhancement methods for PCMs include the use of different shapes and orientations of fins, arrangement of PCMs with various melting points, and the use of carbon and metal-based materials as heat transfer enhancers. Active heat transfer enhancement techniques, which require external power, have also been explored, including mechanical aids, vibration, jet impingement, injection, and external fields. Furthermore, the performance of nanofluids over microporous surfaces has been studied to enhance nucleate boiling heat transfer in thermal management applications.
What are the different ways to improve heat transfer in two-phase flow?5 answersThere are several techniques to improve heat transfer in two-phase flow. One approach is to use nanofluids, which are base fluids with added nanoparticles that enhance thermal conductivity. Another method is to use helically coiled tubes, which create secondary flows that improve heat transfer. Additionally, the use of ferrofluids, which are magnetic nanofluids, can significantly enhance heat transfer rates in microchannels. By adding a small amount of thermally conductive paramagnetic particles to the base fluid, the thermal conductivity can be increased, and applying a magnetic field can further enhance heat transfer. Co-flowing two immiscible fluids in direct contact is another way to enhance heat transfer in minichannels. By analyzing different fluid combinations and conducting a parametric study, it is possible to identify the factors that augment heat transfer in this approach.