Analysis Of Convective Heat Transfer Research Articles

Analysis of Natural Convection Heat Transfer and Solidification within a Corium Simulant

Analysis of Natural Convection Heat Transfer and Solidification within a Corium Simulant

TWO-PHASE MODEL IN POROUS MEDIUM CONVECTIVE HEAT TRANSFER ANALYSIS WITH HIGH POROSITY, CASE STUDY: MINICHANNEL EQUIPPED BY MICROPINS

TWO-PHASE MODEL IN POROUS MEDIUM CONVECTIVE HEAT TRANSFER ANALYSIS WITH HIGH POROSITY, CASE STUDY: MINICHANNEL EQUIPPED BY MICROPINS

Numerical analysis of forced convection heat transfer in a nuclear fuel storage vault

Forced convection heat transfer from fuel and blanket subassemblies to air in a nuclear fuel storage vault has been investigated in this work. Three dimensional simulations were performed for an actual fuel storage vault to improve the decay heat removal, air exchange rate, and thermal effectiveness. Forced airflow was used to remove the decay heat and an efficient ventilation arrangement was rigorously studied for long˗term storage of the nuclear fuel. The height of the interconnecting ducts between the blanket and fuel storage enclosures was systematically investigated to understand the ventilation performance. For this purpose, different temperature and air distributions inside the vault were analyzed. The mixing of air was enhanced, and the thermal stratification was reduced by connecting the ducts above the heat generating region. However, the fuel magazine temperature was reduced when the ducts were connected below the heat generating region. Furthermore, the effect of different shapes of interconnecting ducts on heat removal and air exchange rate through the vault was investigated. It was found that incorporating nozzles in the interconnecting ducts has led to an enhancement in air jet penetration and consequently a reduction in hot spot temperature. The validated computational model will be helpful in designing different aspects of nuclear fuel storage systems.

Numerical analysis of convective heat transfer on straight finned tube with different nano fluids

The major idea of this effort is to study and analyse heat transfer through a straight finned duct with different nanofluids. Dynamics and simulations for fluid flow at the start of fully developed laminar flow with nanofluids in a circular duct with and without fins under constant wall temperature conditions are performed by using fluent commercial software. Heat transfer behaviours of the duct are investigated for constant wall temperature conditions for oxides of nanofluid. The thermal properties of nanofluid are considered from the literature. Commercial software ANSYS 2018 was used to compute the velocity and thermal analysis between the inlet and outlet of the tube. The finite volume method will be used to discretize the whole domain in quadratic elements considered with the turbulence model. Turbulence differential equations system coupled with the heat convection. The flow and pressure, the temperature in the exit will be calculated as a function of initial conditions in the entrance of the duct. The fluid properties such as conductivity and viscosity of the base fluid are taken as temperature independent. The enhancement in heat transfer rate are presented graphically with the effect of effects of nanoparticle volume fraction, nanoparticle size.

Motion of Liquid Convective Flow and Heat Transfer Analysis of Flame Spread over butanol fuel within narrow channels

In actual fire, a solid wall is commonly established using nearby noncombustible solid materials to resist flame propagation. However, there are always some narrow channels owing to uneven surface of solid materials. There are inherent differences between liquid flame spread in narrow channels and infinite width fuel, including dynamic shear and heat dissipation. The experiments of flame spread over n-butanol fuel in narrow channels with lengths of 30, 50, 100, 200 and 300 mm and widths of 3, 4, 5, 6, 7, 8, 9 and 10 mm are carried out. The flame spread is divided into initial stage, restriction stage and jet flow stage. The velocity of subsurface flow decreases strongly once the convective flow enters narrow channel. Based on the assumption that surface tension is balanced with sum of viscous force and shear force, the velocity of subsurface flow at restriction stage is calculated which overestimates ∼10% of measurement. The flame cannot pass through the channel when heat loss accounts for more than 43% of total heat flux of subsurface flow. The heat absorption by sidewalls always accounts for more than 80% of total heat loss. The current finding provides a theoretical guidance for actual liquid firefighting.

Theoretical analysis of unsteady convective heat transfer from a flat plate with time-varying and spatially-varying temperature distribution

Convective heat transfer due to laminar, incompressible flow past a flat plate has been extensively researched due to applications in a variety of engineering systems. In several cases, such as thermal management of Li-ion cells and phase change based energy storage, the flat plate temperature may vary as a function of both time and space, and the resulting plate heat flux is of interest. This paper presents an integral method based analytical model for predicting the heat flux distribution from a flat plate with a time-varying and spatially-varying temperature. Third-order Karman-Pohlhausen polynomial forms of velocity and temperature distributions are used in the integral energy equation to derive an ordinary differential equation that predicts the plate heat flux distribution in response to an arbitrary time- and space-dependent plate temperature distribution. The generalized results derived here are shown to reduce to previously reported results for special cases of only time-dependent or only spatially varying or constant plate temperature. Results are also shown to be in good agreement with finite-element simulations. The analytical model developed here is used to predict the plate heat flux in response to realistic plate temperature distributions that may be encountered in practical applications. These results improve the fundamental understanding of an important convective heat transfer process, and may help in the design and optimization of a broad variety of engineering systems involving convective heat transfer.

Periodical Analysis of Convective Heat Transfer Along Electrical Conducting Cone Embedded in Porous Medium

Periodical Analysis of Convective Heat Transfer Along Electrical Conducting Cone Embedded in Porous Medium

Analysis of convective condensation heat transfer for moist air on a three-dimensional finned tube

The condensation of moist air plays an important role in daily life and industry. During the condensation process, single-phase and phase-change heat transfers occur simultaneously. A three-dimensional finned tube is an effective element for enhancing heat transfer. However, the latent and sensible heat transfer during moist air condensation outside a three-dimensional finned tube has not been experimentally studied. In this study, experiments were performed using a three-dimensional finned tube to enhance the moist air condensation process. For a better understanding of the enhancement mechanism, latent and sensible heat transfer variations with relative humidity ranging from 0.75 to 0.95 and Reynolds numbers ranging from 838 to 3444 were obtained and analysed. A smooth tube was used for the comparison. The experimental results indicated that the three-dimensional finned tube was favourable for the enhancement of moist air condensation, especially for latent heat transfer. When the Reynolds number was 2504, the latent and sensible heat transfers of the three-dimensional finned tube were 43.6%–81.8% and 15.6%–22.9% higher than those of the smooth tube, respectively. In addition, the latent and sensible heat transfers of the three-dimensional finned tube and the smooth tube were obtained under different velocities of moist air, and empirical correlations were developed to predict the sensible and latent heat transfers with deviations of less than ± 20%. The results obtained can provide a reference for the design of three-dimensional finned tubes used in moist air condensation.

Analysis of temperature field and convection heat transfer of oil-air two-phase flow for ball bearing with under-race lubrication

PurposeUnder-race lubrication can increase the amount of lubricating oil entering a bearing and greatly improve lubrication and cooling effects. The oil-air two-phase flow and heat transfer characteristics inside a ball bearing with under-race lubrication play a key role in lubrication and cooling performance. The purpose of this paper is to study these two characteristics, and then provide guidance for lubrication and heat dissipation of bearing with under-race lubrication.Design/methodology/approachIn this paper, a simplified three-dimension heat transfer model of ball bearing with under-race lubrication is established; the coupled level set volume of fluid method is used to track the oil-air two-phase flow, and the Palmgren method is used to calculate the heat generation. The influence of rotation speed and inlet velocity on oil volume fraction, temperature and convection heat transfer is investigated. A temperature test for under-race lubrication is carried out.FindingsBecause of the centrifugal force, lubricating oil is located more on the outer ring raceway. As the rotation speed decreases and the inlet velocity increases, the oil volume fraction increases and the temperature decreases. Furthermore, the area with high oil volume fraction has a large convection heat transfer coefficient and low temperature. The error between the simulation temperature and the test temperature is within 10%.Originality/valueThe research on the temperature field and convection heat transfer characteristics of under-race lubrication ball bearings at different rotation speeds and inlet velocities is rarely involved.

Effects of The Rotation and A Magnetic Field on The Mixed Convection Heat Transfer Analysis for The Peristaltic Transport of Viscoplastic Fluid Through A Porous Medium in Asymmetric Channel

In this paper, we study the impact of the variable rotation, magnetic field and different variable such as the rate flow, Grashof number, Bingham number, Brinkman number, density, viscosity and …etc, on the mixed convection heat transfer analysis for the peristaltic transport of viscoplastic fluid through the porous medium, consideration small Reynolds number and long wavelength, peristaltic transport in asymmetric channel tapered horizontal channel and possess to different amplitude and phases difference. Series solutions for the axial velocity, stream function, stress at the upper and lower channels, temperature and pressure gradient. The impact of parameters discussion and illustrated graphically through the set of figures.

Convection Heat Transfer Analysis with Flow Resistance for Mini-Helically Coiled Tubes at Supercritical Pressures Experimentally

This paper analyzes the effect of fluid flow characteristics on the convection heat transfer for mini-helically coiled tubes (HCT) using supercritical carbon dioxide (CO2) as a natural refrigerant. Two experimental cases have studied in this work for mini-helically coiled tubes at different diameters with different coil pitches for analyzing the convection heat transfer with flow resistance. In the first case, the inner tube diameter, coil diameter and coil pitch were 5 mm, 200 mm and 10 mm respectively, while 10 mm, 100 mm and 5 mm were for the second case. Moreover, this work has also investigated the influence of frictional pressure drop, heat flux, friction factor and mass flux on dimensionless exergy destruction. The work environments were 300-500 K as an inlet temperatures range, 200-2000 Kg / (m2. s) as a mass heat fluxes range, 50,000-500,000 as a Reynolds number (Re) range and 50-200 Kw/m2 as an inner heat fluxes range. As a result, a large effect has been observed for dimensionless exergy destruction compared with the flow friction of CO2 which induced by heat transfer irreversibility. On the other point of view, a good sensitivity of optimal Re with the tube dimeter and mass flux also noticed compared with the heat flux. At a suitable range for Re, smallest and best exergy destruction also noticed for the tube diameters. A correlation has for the optimal Reynolds number as function of main dimensionless parameters related to wall heat flux, mass flux, fluid properties and geometric dimensions is proposed. Characteristics of the fluid flow had influenced significantly by mass and heat fluxes. In the future, the collected experimental data can be employed in order to design and improve the refrigeration conditioning performance for exchangers and other systems such as heat pumps.

Numerical simulation of heat transfer performance and reliability design of road snow-melting system based on inorganic heat pipe

In order to study the optimal design parameters of the heat pipe system in the heat pipe snow-melting road structure, a finite element analytical model of the snow-melting road is established based on the heat transfer theory. And based on the analysis of internal heat transfer and surface convective heat transfer of the road, the author set suitable boundary conditions of temperature field according to the actual situation of the road pavement and made quantitative research on the influence of factors such as the evaporating section burial depth and arrangement distance of the heat pipe on the pavement temperature field. The results show that the optimal arrangement distance of the heat pipes is 300-500mm, and when the heat pipe distance is 500mm, the temperatures of the road surface increased slowly, the isotherm of 0°C will no longer continue, and the snow-melting time would become longer; heat pipe burial depth should be determined according to the road structure, the shallower the burial depth the better the snow-melting effect..

Forced Convective Heat Transfer Analysis for Two-dimensional Slot Jet of Water-CuO Nanofluid

This paper investigates the effect of the diameter and the volume fraction variation of the centre nanoparticles on the heat transfer characteristics of a two-dimensional slot jet. The jet impinges on stationary flat, convex, and concave aluminium plates. A forced convective heat transfer coefficient of water-CuO nanofluid impinges on a smooth plate under a constant heat flux. The finite volume method (FVM) is implemented for nanoparticles with diameters varying from 7 to 60 nanometers, volume fractions changing from 0 to 5%, and the Reynolds numbers ranging from 1800 to 2800. A grid independence study is carried out to find a grid size that predicts the results accurately and further grid refinement changes the results insignificantly. The single-phase model shows a capability to predicts the fluid and heat transfer parameters faster and make it more suitable for numerical simulations compared to the two-phase model. The results indicate a higher heat transfer coefficient of nanofluid in comparison with distilled water. As the Reynolds number and nanoparticle volume concentrations increase, the heat transfer rate increases on the surface whilst smaller nanoparticle diameters increase during the cooling process. The increase in the diameter of nanoparticles enhances the Nusselt number on the plate by up to 10%. The same geometrical details, thermophysical, and boundary conditions have been employed in all calculations for distilled water jet simulations to validate the fluid flow behaviour and heat transfer parameters with available experimental data in the literature.

Numerical optimization of a conical cavity as a radiation-focused concentrator

Conical enclosures rely on the conical cavity and can be used as radiation concentrators. Two circular cross-section baffles were used to improve the heat transfer of this geometry. By changing the rigid fins to porous, it could improve the heat transfer. Al2O3/water nanofluid was also employed to enhance the heat transfer performance of the cavity. For this purpose, numerical analysis of three-dimensional natural convection heat transfer was performed in a conical cavity with two types of fins. The best combination of fins arrangement for the next step was selected using the differential evolutionary optimization method (D.E). In this case study, a new combination of laminar and turbulence methods was employed for the first time to increase the accuracy of the natural convection solution. This combination is based on the laminar solution by suppressing the perturbation parameter in the turbulence method which led to more accurate results. The analysis results showed that a conical cavity with optimized fin geometry can lead to a 23% increase in Nu. The best porosity for the inner fin was calculated 40% in the case of constant porosity. Ascending porosity along the fin, whose increase was more intense near the base and slower near the cone's tip, was the best variable porosity for the inner fin.

Analysis of convection heat transfer on multiscale rough superhydrophobic and liquid infused surfaces

Multiscale rough superhydrophobic or slippery liquid infused porous surfaces have gained much interest in recent years for their improved transport phenomena properties. While there have been several studies on drag reduction and condensation on non-wetting surfaces, convection heat transfer that is important in many thermal and thermochemical applications has not been addressed systematically. This article utilizes a fractal description of rough surface topographies to develop analytical models for the Nusselt number and the thermal hydraulic factor for fluid flow and heat transfer inside a cylinder with non-wetting surfaces. For air-infused superhydrophobic surfaces, the model considers the dynamic stability of the air/fluid interface in the asperities. Using the analytical formulations and the stability criteria, systematic studies are presented on the effects of the fractal surface parameters, cylinder radius and Reynolds number on the convective heat transfer characteristics, from which surface texture design maps are developed for maximizing the convection heat transfer. It is shown that multiscale non-wetting surfaces are most effective in the range of lower Reynolds number and small cylinder radius for achieving the best convective heat transfer and thermal hydraulic performance. Applying the models to actual non-wetting surface topographies fabricated using electrodeposition and chemical etching, it is shown that contrary to prevailing notion, superhydrophobicity, characterized by the highest contact angles, does not always lead to the maximum convective heat transfer performance, and that under certain fluid flow conditions, hydrophobic surfaces may offer a greater thermal performance.

Numerical investigation and ANN modeling of the effect of single-phase and two-phase analysis of convective heat transfer of nanofluid in a cavity

The goal of this numerical investigation is to explore and compare the hydrothermal characteristics of free, mixed, and forced convection of water-copper nanofluid in a cavity using single-phase (SPM) and two-phase (TPM) methods. The top and bottom walls of the cavity are insulated, and the left and right walls are kept at a constant temperature so that the temperature of the left wall is higher than that of the right wall. The impact of volume fraction of nanoparticles ( $$\varphi$$ ), Rayleigh number (Ra), Richardson number (Ri) and Reynolds number (Re) on the performance features is assessed. In addition, the artificial neural network (ANN) is employed to develop a predictive model of average Nusselt number of nanofluid. The results showed that the TPM was more accurate than the SPM. Additionally, it was observed that increasing the $$\varphi$$ , Ra, Ri and Re leads to increasing the average Nusselt number of nanofluid. The maximum heat transfer improvement for the mixed convection and forced convection modes was 28% and 32%, respectively. Furthermore, the ANN modeling revealed the nanoparticle concentration has a negligible role on the results of free convection, while the opposite is true of forced convection.

CFD analysis of natural convection heat transfer in a static domestic refrigerator

Refrigerating compartment with and without shelves is designed for analyzing the air flow and temperature distributions by using the Simulation software Ansys work bench 14. Comparing the results of the air and temperature distributions inside the refrigerating compartment with and without shelves. Here shelves considered as obstacles and the refrigerator without freezer compartment is considered as a 2D rectangular enclosure one side is assumed as evaporator wall (cold wall) and other side as Door (warm wall). Inside the refrigerator cabin air flow takes by natural convection. Temperature distributions is observed in the compartment without shelves and with shelves and same is compared. In the natural convection heat transfer happens between the internal walls of the refrigerator and air by radiation, conduction and convection. Air flows downward near the cold wall and moves upward near warm wall due to the density variation. As a result, temperature stratification was observed in the refrigerating compartment. Evaporator wall maintains the colder region and door wall has the higher temperature.

Numerical analysis of mixed convection heat transfer and laminar flow in a rectangular inclined micro-channel totally filled with Water/Al2O3 Nano fluid

A numerical analysis was carried out of mixed convection heat transfer for a laminar flow in a rectangular inclined microchannel totally filled with a water/Al2O3 nanofluid. The governing conservation equations are translated into a dimensionless form using the thermal single relaxation time and they modify the lattice Boltzmann method with double distribution functions. The viscous dissipation effects are adapted to the energy equation. The effects of nanoparticle volume fractions ϕ (0 ≤ ϕ ≤ 0.04) and inclination angles γ (0° ≤ γ ≤ 60°) on the flow of the nanofluid and the heat transfer are investigated. The obtained results are presented in terms of streamlines, isotherms, slip velocity, wall temperature and Nusselt number. The results show that the higher values of the volume fraction of Al2O3 and the large values of inclination angles improve the heat transfer rate.

Influence of MHD on mixed convective heat and mass transfer analysis for the peristaltic transport of viscoplastic fluid with porous medium in tapered channel

In this paper, the influence of magnetohydrodynamic (MHD) on a mixed convective heat and mass transfer analysis for the peristaltic transport of viscoplastic fluid in a non-uniform two dimensional tapered asymmetric channel with porous medium is investigated. The governed equations that described the motion of flow are simplified under assumptions of low Reynolds number and long wavelength. These equations are solved by mean of the regular perturbation method which is restricted to the smaller values of Bingham and Grashof numbers. Series solution for the axial velocity, temperature and concentration distribution have been computed. The flow quantities have been illustrated graphically for different interesting parameters. The trapping phenomena is also examined graphically

Analysis of forced convective heat transfer through nanofluids around a square cylinder using Eulerian-Eulerian mixture modelling

Numerical analysis of laminar forced convective heat transfer of Al2O3-H2O nanofluids around a square bluff body is presented. An Eulerian-Eulerian approach-based mixture model, considering the sli...