Convective Heat Transfer Research Articles

Modelling of radiative and convective heat transfer in an open cavity volumetric receiver for a 50-MWth beam-down integrated receiver-storage concentrating solar thermal system

Modelling of radiative and convective heat transfer in an open cavity volumetric receiver for a 50-MWth beam-down integrated receiver-storage concentrating solar thermal system

The effect of rotating magnetic turbulators on the convective heat transfer and pressure drop through a circular tube: Experimental investigation

The effect of rotating magnetic turbulators on the convective heat transfer and pressure drop through a circular tube: Experimental investigation

Using of multi-phase thermal model of the lattice Boltzmann method for simulation of two-phase Rayleigh–Bénard convective heat transfer

Using of multi-phase thermal model of the lattice Boltzmann method for simulation of two-phase Rayleigh–Bénard convective heat transfer

Differences for Cooling Capacity of a Cable Tunnel System: Install One or Three Additional Cable Troughs with Cable Circuit for 100/70 Heat Loads – A Numerical Study

The purpose of this report was to compare the numerical analysis for different cooling efficiency of a cable tunnel system when installing one additional cable trough or three cable troughs for cable circuit 100% or 70% heat load. Cable tunnel system is widely known for it is use for high voltage transmission in an underground. Due to the cables generating large quantities of heat, water pipes and air ventilation were used in the tunnel to cool down the transmission cable. To investigate the cooling efficiency of a tunnel, research for benchmark case was carried out. A Computational Fluid Dynamic (CFD) benchmark analysis about 2D natural convection inside the square cavity was investigated to further understand the air movement inside the square medium. Ansys Fluent was carried out for benchmark cases of heat transfer natural convection inside the square cavity and to check whether Ansys Fluent can be used for any CFD and heat transfer purposes by validating the results with previous studies. The benchmark case used a 2D square with different active temperature side walls and adiabatic walls for top and bottom side. From the benchmark simulations with different Rayleigh Number, a number representing buoyancy-driven of a fluid from 103 to 105 affected air differently and the heat transfer natural convection inside the square. At different Rayleigh Number air forms a recirculation passing the active walls and adiabatic walls. After investigated the benchmark, the results were used to validate with previous studies. To validate the results was by using Nusselt Number, ratio of convective to conductive. The benchmark case results were validated and Ansys Fluent proven can be used for CFD and heat transfer purposes. Two 3D cable tunnel were modelled with 100-meter length after concluded the benchmark. The two tunnel models were based on the number of cable troughs installed. The first tunnel was with one cable trough and two cable circuits on the bottom, as for the second tunnel was with one bottom cable circuit and three cable troughs. Cable tunnel simulations were based on cable circuit for 100% heat load and 70% heat load with each heat load case was given different water flow rate of 4.25 L/s and 6.5 L/s. A total of eight scenario cases were carried out to determine which provided a better cooling efficiency choice. The analysis for cable tunnel cases on how the copper cables cooled down through heat transfer of natural convection inside the cable trough, which the heat then was removed from the cable circuit by air and continue to the outside of the tunnel. During the heat transfer processes, conductivity was present as not all heat were removed by air and water, but continue to through the walls of the tunnel and to the ground soil. Based on the simulations, a cable tunnel with three cable troughs was proven more cooling efficiency compared tunnel with one cable trough. Some scenarios did not meet the criteria, due to insufficient heat relocation by air and water. The cooling efficiency was determined by which has the better balance heat relocation by air, water, and ground, also considering the comfort and safety of human inside the tunnel.

Exploration of Arrhenius activation energy and thermal radiation on MHD double-diffusive convection of ternary hybrid nanofluid flow over a vertical annulus with discrete heating

The primary objective of this article is to examine the effect of discrete heating on MHD double-diffusive convection and thermal radiation of ternary hybrid nanofluid flow heat and mass transfer in a vertical cylindrical annulus along with Arrhenius activation energy and chemical reaction. In this study, the cavity inner wall has two distinct flush-mounted heat sources, while the outer wall is isothermally cooled at a lower temperature. The top and bottom walls are thermally insulated. The ensuing equations that govern the physical framework are solved using the implicit Crank-Nicholson finite difference technique. As the heater advances upward, the flow intensity decreases, leaving a part of the fluid static at the bottom of the cylinder. Because more heat induces high buoyant flow in the annulus, the absolute value of axial velocity and wall temperature rises as the length of the heat source rises. Enhancing the activation energy parameter values drops the Arrhenius energy function, elevating the pace of the generative chemical process and hence the concentration. Increasing the thermal radiation parameter lowers the surface heat flux while enhancing the nanofluid temperature. The Brownian motion parameter corresponds to the random motion of nanoparticles in a fluid, and this irregular movement augments the collision of nanoparticles with fluid particles, causing the particle's kinetic energy which leads to thermal energy and hence increases temperature, a 10% increment in Brownian motion parameter leads to 26% rise in the temperature. Also, the heat and mass transfer characteristics are forecasted and analyzed by considering the Levenberg–Marquardt backpropagating artificial neural network technique.

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

Dynamic features of heat transfer in a square enclosure induced by an adiabatic rotating circular cylinder with double‐diffusive buoyancy forces

The study discusses steady‐state double‐diffusive convective heat and mass transfer (HMT) in a square enclosure containing a clockwise rotating adiabatic cylinder located in the center of the enclosure. The model is a 2‐D square enclosure. The left vertical wall of the enclosure is the higher concentrated‐heated wall, the right is the lower concentrated‐cold wall, T while the cylinder and the horizontal walls of the enclosure are thermally insulated with zero‐mass flux. The descriptive equations were solved by the finite element method for . The implications of cylinder size , cylinder rotational‐speed , Lewis number , buoyancy ratio , and Richardson number on concentration, streamlines, and isotherms are reported. Furthermore, the responses of HMT to the parameters of interest were presented in terms of Nusselt and Sherwood numbers. Results showed that while increasing both the cylinder size and the rotational speed of the cylinder were found to augment both heat and mass transfer, the maximum heat and mass transfer occurred at of the concentrated‐heated wall length, and a critical buoyancy ratio of , for which both HMT were maximized was established. Finally, both HMT diminished as Ri increased. This study provides a pathway for performance improvement in micro‐chip‐cooling in the electronic industry, drying technology, and heat exchangers. The impacts of cylinder rotation and size on HMT for the configuration investigated had not been previously investigated. Furthermore, the study established a critical buoyancy ratio value that ensures maximum heat and mass transfer enhancements.

Preface

It is our great pleasure to present the Proceedings of the 41st UIT International Heat Transfer Conference, held from 19 to 21 June 2024 at the Congress Centre of the Università degli Studi di Napoli Federico II, organized by the Dipartimento di Ingegneria Industriale. This year, the conference held special significance as it took place within the events celebrating the eight hundredth anniversary of the foundation of the Università degli Studi di Napoli Federico II, a milestone underscoring the university’s long-standing tradition of excellence in education and research. The conference was attended by approximately 180 participants, including 85 members of the UIT community, 40 non-members, and 55 students. The sessions were dedicated to key topics such as Computational Fluid Dynamics, Conduction Radiation and Thermophysical Properties, Heat and Mass Transfer in Energy Systems and Nuclear Plants, Natural, Forced, and Mixed Convection, Micro and Nano-Scale Heat Transfer, and Multiphase Heat Transfer. The program featured three keynote lectures, during which distinguished speakers shared their insights on pressing issues and emerging challenges in the field. Additionally, the Program Manager of the European Innovation Council presented valuable opportunities for transferring research into innovation, bridging the gap between academia and industry. List of Conference Chairs, Scientific Committee, Organizing Committee, Sponsors and Editors contact details are available in this Pdf.

Experimental investigation on non-linear flow and convective heat transfer of damaged multi-fractured rock

Experimental investigation on non-linear flow and convective heat transfer of damaged multi-fractured rock

Infrared thermography applied to the study of the local heat transfer enhancement in a wall corrugated tubular heat exchanger for food applications

Abstract The combination of global and local performance analysis represents a powerful tool for the optimal design and sizing of heat exchangers, especially when wall corrugations are employed to enhance inner convection. In this paper, both approaches are applied to a transversely corrugated pipe to propose a thermal correlation and investigate the effects of corrugation on the local heat transfer performance. For the local analysis, infrared thermographic measurements, combined with the solution of the inverse heat conduction problem in the solid wall domain, were used to evaluate the internal convective heat transfer coefficient. The combined approach offers a valuable tool for the optimal design of heat exchangers and related thermal processes, particularly in applications where knowledge or prediction of the local temperature-time history of fluid particles is critical. This is especially relevant in the food industry, where such passive heat transfer enhancement solutions are widely used.

Effects of fluid–structure interaction on natural convection heat transfer in a square cavity divided by vertically flexible walls

Effects of fluid–structure interaction on natural convection heat transfer in a square cavity divided by vertically flexible walls

Comparative investigation of the energy consumption and heat transfer characteristics of Uni-modal and Bi-modal slurry flow through a straight pipe

Slurry transport via pipelines is a widely used method across various industries globally. While extensive research exists on optimizing parameters for efficient slurry pipeline systems, studies on the optimal combination of two mixtures to maximize efficiency in bi-modal slurry transport remain limited. This research addresses the gap by developing a three-dimensional computational model to examine the energy, transport, and thermal characteristics of mono-dispersed and bi-modal slurries. The model compares these characteristics with the behavior of pure water flowing through a straight pipe, providing insights into how slurry composition affects flow dynamics and heat transfer. The study investigates slurry flow through a round straight pipe at Reynolds numbers ranging from 128,035 to 320,000 and volumetric concentrations (Cvf = 10–40 %). The bi-modal slurry consists of silica sand and fly ash mixtures in proportions of 85:15 and 65:35, while the uni-modal slurry has proportions of 100:0 and 0:100. Computational results indicate that the 65:35 mixture, flowing at Re = 128035 and Cvf = 10–20 % achieves the lowest pressure drop and specific energy consumption (SEC), enhancing transport efficiency. Furthermore, wall shear stress (WSS) and energy consumption increase with higher Reynolds numbers and volumetric concentrations. Notably, the 100:0 mixture achieves the highest convective heat transfer coefficient, which increases with Reynolds number and volumetric concentration.

Investigation of natural convection heat transfer in MHD fluid within a hexagonal cavity with circular obstacles

Investigation of natural convection heat transfer in MHD fluid within a hexagonal cavity with circular obstacles

Heat transfer in the entrance region of annular laminar flow with constant and different heat flux on two walls

AbstractHeat transfer differs in the regions where the flow is developed and developing thermally. These regions can be differentiated by using the thermal entry length. Many researchers have presented correlations to determine the thermal entry length for natural and forced convection. In this study, heat transfer in the entrance region of a concentric annuli is investigated. It is accepted that beginning from the inlet of annuli the flow is developed hydrodynamically and it is developing thermally. Heat transfer is investigated where the internal or external surfaces of the annuli are at constant but different heat fluxes. The fluid velocity is assumed to be constant or radially variable. Due to thermal boundary conditions, one thermal boundary layer appears on the outer cylinder surface, another on the inner cylinder surface. The edge of two boundary layers will be adiabatic and naturally, the temperature of fluid between the two edges will be equal to free stream temperature. Transformation, Separation of Variables method, eigenvalue problem, Sturm‐Liouville system, Bessel differential equation and properties of orthogonal functions are used in solution of the problem. Exact and analytical solutions of the momentum and energy equations are presented. Velocity and temperature distributions, local Nusselt numbers and convection heat transfer coefficients are calculated for the internal and external surfaces of annuli.

Physics-informed graph neural network based on the finite volume method for steady incompressible laminar convective heat transfer

Physics-informed graph neural network based on the finite volume method for steady incompressible laminar convective heat transfer

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.

Possibilities of Calculation of Convection Heat Transfer inside Built-up Urban Area

Possibilities of Calculation of Convection Heat Transfer inside Built-up Urban Area

Natural convective heat transfer in a square cavity with a curved hot wall partially heated from below

Natural convective heat transfer in a square cavity with a curved hot wall partially heated from below

Human body convective heat transfer coefficient under non-stationary turbulent wind

Human body convective heat transfer coefficient under non-stationary turbulent wind

Impact of human body shape on free convection heat transfer.

Understanding the thermal comfort and safety of diverse populations within indoor settings requires a quantitative understanding of the primary heat exchange pathways between occupants and their surroundings: radiation and free convection. Thus far, however, free convective heat transfer coefficients have only been determined for the average Western adult. To this end, we investigated how variation in body shape impacts free convection heat transfer using an experimentally validated numerical model. The multiphysics model was compared against experiments conducted using the thermal manikin ANDI ("Advanced Newton Dynamic Instrument") in a climate-controlled enclosure across five air-to-skin temperature differences ranging from 4.9 to 13.9°C. The difference between measured and simulated heat fluxes for the whole body, and per anatomical region, was typically <5%, occasionally reaching 15-20%, for some body regions due to physical features not modeled in the virtual ANDI model. Using the validated model, we simulated free convection around a family, or diverse group, of virtual manikins representing the 1st to 99th percentile body mass index (BMI) and height variation in the United States adult population. Our results show that the free convection heat transfer coefficient is independent of human sex and height but decreases slightly with increased BMI. However, the variation from the average manikin in the whole body and regional free convection coefficients with BMI was small, not exceeding 8% and 16%, respectively. Furthermore, our regression coefficients and exponents can be derived from the theorical correlation for free turbulent convection from a vertical plate, which also explains the observed independence of the heat transfer coefficient from the manikins' height. Overall, these findings demonstrate the general applicability of using an average body shape in indoor thermal audits and/or overheating risk assessments to understand thermal comfort and heat stress. The results and valid application of the model support critical insights for human health, productivity, and well-being connected to heat and cooling in buildings.