Convective Heat Transfer Research Articles

Impact of non-linear motion on convective heat transfer induced by oscillating thermal waves in the presence of heat source and sink

Impact of non-linear motion on convective heat transfer induced by oscillating thermal waves in the presence of heat source and sink

Experimental and numerical studies of laminar natural convection heat transfer from an isothermally heated narrow flat plate oriented at different angles of rotation

Experimental and numerical studies of laminar natural convection heat transfer from an isothermally heated narrow flat plate oriented at different angles of rotation

Numerical analysis of natural convective heat transfer with porous medium using JUPITER

ABSTRACT Japan Atomic Energy Agency (JAEA) has developed a numerical method with the JUPITER code with a porous medium model to calculate the thermal behavior in primary containment vessels (PCVs) of Fukushima Daiichi nuclear power stations of Tokyo Electric Power Company (1F). In this study, we performed an experiment and numerical simulation of the natural convective heat transfer with the porous medium and compared those results. In comparison of the temperature and velocity distributions between the experiment and simulation, the temperature distribution in the simulation was in good agreement with the distribution in the experiment except the temperature near the top and side surface of the porous medium. The velocity distribution also agreed qualitatively with the experimental result. In addition, we also performed the numerical simulations with various effective thermal conductivity models to discuss the effect of the conductivity based on the internal structure of porous media on the natural convective heat transfer. The result indicated that the temperature distribution in the porous medium and the velocity distribution of the natural convection were significantly different for each model, and the simulation result with the Kunii–Smith model was close to the experimental results.

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 analysis of superconducting motors for electrical aircraft propulsion using electromagnetic–thermal coupling method

The aviation industry is focusing on the development of low-carbon emission technologies, with hydrogen-powered aviation hybrid technology being an important area of interest. Superconducting motors (SCMs) play a crucial role in these aviation hybrid systems due to their high power-to-weight (PTW) ratio. However, SCMs face challenges such as strong coupling of the electric field, magnetic field, and temperature field within the motor. Conventional electromagnetic–thermal coupling analysis methods are not suitable for SCMs, as they are slow to perform calculations that are also less accurate. This study proposes an electromagnetic-thermal coupling analysis model for SCMs, taking into account the constraints of critical current, critical magnetic field, and critical temperature of superconducting (SC) materials. The study analyzes the impact of the critical current of SC tapes, permanent magnet remanence, convection heat transfer coefficient between SC coils and cooling medium, AC loss reduction of SC coils, and motor speed on the ultimate power of SCMs. The results show that an optimal permanent magnet remanence can maximize the ultimate power, and the other parameters have been found to be positively correlated with the ultimate power of the SCM. To enhance the PTW ratio of SCMs, future research directions include increasing the critical current of SC materials, reducing the AC loss of SC coils, and improving the cooling effectiveness of SC coils.

Numerical investigation on hydrothermal characteristics of microchannel heat sinks with PCM inserts for effective thermal management applications

PurposeThe purpose of the paper is to develop an efficient thermal management system, which effectively dissipate the heat generated from the electronic devices. The present paper focuses at the modeling of microchannel heat sinks (MCHSs) with phase change materials (PCMs) insets to deal with the fluctuating heat generated from the electronic components.Design/methodology/approachIn this paper, a novel approach is introduced to enhance the thermal performance of MCHSs through the integration of conjugate heat transfer and energy storage. Numerical investigations were conducted on six novel models of PCM-based hybrid MCHSs using ANSYS-FLUENT. The hydrothermal characteristics of six PCM-based hybrid MCHS models were analyzed and compared with an MCHS model without PCM.FindingsThe numerical model used for this study exhibited a good agreement with existing experimental and simulation results documented in the literature. The hybrid MCHS models developed in the present analysis showed superior thermal characteristics compared to MCHS without PCM. About 12% improvement in the thermal performance factor and a 7.3% reduction in thermal resistance were observed in the proposed MCHS models. A negligible influence of the PCM channel shape and aspect ratio (AR) was observed on the MCHS performance.Research limitations/implicationsAs the present work is a numerical investigation, the computational time and computational cost requirements are the main implication for the research.Practical implicationsHigh pumping power requirement and expensive manufacturing methods of the microfluidic devices are the main practical implications. Leakage problem is also a challenge for development of these heat sinks.Originality/valueThe surge in the heat generated by electronic components is a limiting factor for the conventional MCHSs. To accommodate the surge, researchers have explored energy storage methods using PCM-based passive MCHS but these are effective only during the phase change process. To address this limitation, novel PCM-based hybrid MCHSs, which combine convective heat transfer with energy storage capabilities, have been modeled in the present work. There is an ample opportunity for further exploration of hybrid MCHSs with PCM.

Improving Thermal Performance in Building Heating, Ventilation, and Air Conditioning Systems: A Study of Natural Convection and Entropy in Plus‐Shaped Cavity

ABSTRACTThe impact of building design on energy efficiency has been widely studied, with cavity cooling emerging as an effective solution for indoor thermal comfort, where obstacles within the cavity can enhance fluid flow and improve natural convection heat transfer (HT). This research builds on the principles of cavity cooling for indoor thermal comfort, investigating entropy generation and HT behavior in a unique plus‐shaped cavity containing a cold cylindrical element, analyzed through Computational Fluid Dynamics simulations. The Rayleigh number (Ra) ranges from 103 to 106, with a fixed Prandtl number (Pr) of 0.71, representing air as the working fluid, radius (r) of the cylinder ranges from 0 to 0.1, where r = 0 indicates no cylinder. The results indicate significant shifts in flow structure and temperature distribution across the cavity at varying Ra values, impacting the local and global entropy generation. High Rayleigh numbers lead to enhanced convective flows, intensifying entropy production near the cylinder surface due to steeper thermal gradients and vigorous recirculation zones. The increase in Ra from 103 to 106 leads to an increase in Nuavg from 24.27 to 56.40 for the model without a cold object while from 39.62 to 123.83 for the model with a cold object. Moreover, the maximum enhancement in Nuavg was 137.48% for Ra = 105. Whereas, for the same value of Ra = 105, the maximum increase in Egen and Be was 474.92% and 33.16%, respectively. Also, a new correlation is proposed to calculate Nuavg using response surface methodology. This study offers a comprehensive examination of heat flow characteristics and entropy generation rates in confined geometries, contributing valuable knowledge to thermal management and optimization in systems with internal obstacles.

Numerical study of natural convection heat transfer in a curve-shaped enclosure with MHD effects and hybrid nanofluids

Numerical study of natural convection heat transfer in a curve-shaped enclosure with MHD effects and hybrid nanofluids

Numerical Study on the Influence of Solutal Buoyancy on Mixed Convection Heat and Mass Transfer in Skewed Domain

This study examines how variations in solutal buoyancy force affect mixed convection heat and mass transfer in a skewed domain. The thermal buoyancy is fixed at 105 for all the cases and mixed convection is induced due to the rotation of a cylinder in clockwise and counterclockwise directions. The solutal buoyancy is varied by changing the buoyancy ratio (0.5, 1, and 1.5). In the present investigation, OpenFOAM 5.0 has been employed to compile the heat and mass transfer solver by coupling energy and concentration equations with Soret and Dufour parameters. The Navier-Stokes equation along with Boussinesq term is included for mixed convection flow analysis. The cylinder rotation is kept constant to maintain the Reynolds number at 1000 at a fixed Richardson number of 1. It is found that for natural convection flow with a stationary cylinder, the heat and mass transfer are higher and stable at low buoyancy ratios. However, for mixed convection flow cases, the increase in heat and mass transfer is maximum and periodic with higher buoyancy ratios.

The Laser Processing of the Stainless-Steel Surface Layer of a Heat Exchanger Membrane in Order to Enhance Its Heat Transfer Coefficient

Research on temperature regulation is essential for ensuring thermal comfort and optimizing machine performance. Effective cooling systems are critical in industrial processes and everyday electronic devices in order to prevent overheating. Laser-modified heat exchangers can enhance heat dissipation without increasing weight, addressing the need for energy-efficient solutions in the market. The main aim of this experimental research was to establish an efficient method for altering the surface layer of AISI 316L stainless steel with laser pulses and to determine the effectiveness of the laser alterations to the surface layer in the context of intensifying the convective heat transfer. A series of laser-texturing processes was performed on the surface layer of AISI 316L steel using a Nd: YAG pulse laser. Selected samples were subjected to a series of measurements using a recuperator-type heat exchanger. Based on the measurements’ results, the heat transfer coefficients, α, obtained from the modified surfaces were determined. The results were compared with other data from the existing literature and those obtained from unmodified reference samples. The intensification of the convective heat transfer was achieved for 43% of the modifications conducted with a pulsed laser. The highest observed average increase in the heat transfer coefficient, α, was 16.53%. However, the effective intensification of the convective heat transfer, in some cases, was only observed for a certain range of temperatures or flow dynamics parameters.

Predictions of cell-to-cell propagation and vent gas production in the thermal runaway of lithium-ion battery stacks

Abstract This work presents the thermal runaway propagation model LIM1TR (Lithium-ion Modeling with 1-D Thermal Runaway) as an efficient tool to predict different cell-to-cell thermal runaway propagation scenarios. We explored the vent gas volume production and reaction duration highlighting the relationship between these parameters and thermal runaway propagation due to convection by the vented gases. Two metrics based on gas production rate and heating rate are utilized as good indicators of the start and end of thermal runaway. LIM1TR results are compared with and validated by experiments from the literature for single-cell and multi-cell array experiments of 5 Ah and 10 Ah cells. By accounting for intra-particle diffusion of reacting species in the electrodes, we were able to capture the general dynamics of thermal runaway propagation and estimate acceptable reaction durations compared with the experimental values. Simulation results further demonstrated that varying heating modes lead to distinct reaction durations, consistent with experimental observations. Vent gas volume predictions indicate the need to consider both full and partial oxidation of the electrolyte. The outcomes of this work are building blocks for further investigations of module-to-module propagation by vented gases through convective heat transfer.

AN INVESTIGATION OVER THE INFLUENCE OF RADIANT THERMAL MAT DIMENSIONS ON ITS RADIATIVE AND CONVECTIVE HEAT TRANSFER CHARACTERISTICS

For living spaces, radiant thermal mats are seen to be a good substitute for traditional heating systems. The natural convection heat transfer properties of radiant heating and cooling systems have been well studied, while the properties of radiant mats placed on surfaces have received relatively less attention. Mats of square and rectangular shapes (<i>a</i> × <i>b</i> = 0.5 m × 0.5 m, 1 m × 1 m, 1.2 m × 1.2 m, 1.4 m × 1.4 m, 1 m × 1.2 m, 1 m × 1.4 m, and 1 m × 1.6 m) are installed on the walls of an enclosure with floor dimensions <i>L</i> × <i>L</i> = 4 m × 4 m and a height of <i>H</i> = 3 m in order to address this gap in the literature. Upon analyzing the complete dataset of local convective heat transfer, it is evident that there is a steady decline in the local convective heat transfer coefficients. This decline commences at the initial point of mats, which corresponds to 3 W/m<sup>2</sup> K. This trend remains rather constant until the impact of turbulence becomes noticeably apparent, which occurs when the mat dimensions are 1 m by 1.6 m. Average convective, radiative, and overall heat transfer characteristics, which are important for building energy simulation programs, are found and correlated for different mat dimensions using the surface-to-surface (S2S) radiation model and the <i>k-ε</i> RNG turbulence model in the numerical program, with error ranges of ± 15%, ± 5%, and ± 5%, respectively.

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

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

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