Influence Of Non-uniform Heating Research Articles

Subchannel thermal–hydraulic analysis of a wire-wrapped 19-pin rod bundle in the NACIE-UP facility

Based on the experimental campaign performed on the NACIE-UP (NAtural Circulation Experiment-Upgraded) facility, the benchmark activity was proposed by ENEA to qualify and validate the numerical tools for the Heavy Liquid Metal (HLM) system. Xi’an Jiaotong University participated in the benchmark exercise of subchannel validation and the self-developed subchannel code YAOGUANG was applied to the thermal hydraulic analysis. The performed two tests with different power distributions on the Fuel Pin bundle Simulator (FPS) were simulated, characterized by transition from forced to natural circulation. The applicability of this code to the stable state and mass flow rate transient was evaluated by comparing the numerical outcomes with the experimental results. Then the effect of the non-uniform heating on the thermal field was analyzed. The results indicate that this subchannel code has good accuracy in simulating both steady state and transient conditions with uniform power distribution. For the non-uniform case, the subchannel calculations can capture the general trend of temperature distributions, with a larger simulation deviation observed. This discrepancy is mainly due to the limitations of existing models adopted because they didn’t consider the impacts of non-uniform conditions on the flow and heat transfer in rod bundles. Finally, the influence of non-uniform heating is mainly manifested as the increase of axial and radial temperature gradients and it helps to flatten the radial thermal field to some degree.

Entropy generation on MHD pulsatile flow of third grade hybrid nanofluid in a vertical porous channel with nonuniform heat source/sink, variable viscosity, thermal conductivity, and Joule heating: A numerical study

This investigation inspects the entropy generation of magnetohydrodynamic pulsating third grade hybrid nanofluid flow between two vertical porous walls under the influence of nonuniform heat generation/absorption. Variable viscosity, variable thermal conductivity, Joule heating, thermal radiation, and slip effects are considered. Blood is taken as base fluid (third grade), iron oxide or magnetite and titanium dioxide are as nanoparticles. The nondimensional quantities are utilized to attain the dimensionless flow governing nonlinear partial differential equations (PDEs) and then the perturbation technique is employed to obtain the set of nonlinear ordinary differential equations (ODEs) from PDEs. The Runge-Kutta 4th order technique along with shooting procedure is utilized to get solutions for the set of ODEs. The variations in different physical quantities on velocity, temperature, heat transfer rate, entropy generation, and Bejan number are depicted via graphs. The velocity enhances for the higher values of Grashof number. Accelerating space and temperature-dependent heat source/sink coefficient accelerates the temperature. The presence of variable viscosity and thermal conductivity intensifies the temperature when compared to their absence. A rise in radiation parameter accelerates the entropy and Bejan number. An increment in Eckert number and radiation parameter increases the heat transfer rate. Intensifying Hartmann number reduces the skin friction.

Effect of thermal radiation on nonDarcy hydromagnetic convective heat and mass transfer flow of a water–SWCNT’s and MWCNT’s nanofluids in a cylindrical annulus with thermo-diffusion and chemical reaction

The examined through analysis of the movement of water-based single wall carbon nanotube (SWCNT) and multiwall carbon nanotube (MWCNT) nanofluids in a coordinate annulated zone under influence of non-uniform heat source/sink. By imposing the appropriate nondimensional variables, the governing partial differential equations are converted into a system of coupled nondimensional partial differential equations. By means of the usage of quadratic polynomials and the Galerkin finite element detail approach, the nonlinear equations have been executed. The expressions representing fluid velocity, temperature and concentration are discussed graphically. While skin friction, heat transfer and mass transfer are revealed in tabular structure. The proposed scheme is shown to have faster convergence than the existing scheme with excellent accuracy. Various parametric values have been analyzed and observed that higher temperatures and concentrations are produced with lower velocities with and bigger velocities with higher radiative heat flux or nanoparticle volume fraction.

Dynamic and sound radiation characteristics of a non-uniformly heated isotropic plate

The influence of non-uniform heating on the anisotropic plate’s dynamic and acoustic response characteristics is investigated numerically. The effect of non-uniform heating on the plate is accounted in the form of pre-stress developed on the plate due to non-uniform heating of the plate. The influence of structural boundary conditions, nature of temperature variation, and level of temperature on vibration and acoustic response characteristics are investigated in detail. Thermal buckling strength and fundamental buckling mode are highly sensitive to the nature of temperature variation across the plate. Free vibration mode shapes of the plates with high aspect ratio and free edges are changing their pattern with an increase in temperature. The resonant amplitude of sound power radiated associated with a particular mode is dominated by vibration nodes and anti-nodes shifting relative to the excitation location. Further, an increase in sound power level with an increase in temperature is observed clearly in the lower octave frequency bands.

Research of two‐phase density wave instability in reactor core channels with rolling motion

In this study, two-phase density wave instability in parallel-twin rectangular channels was investigated with axially nonuniform heat profiles in the reactor core combined with static and rolling conditions. A parallel-channel thermal-hydraulic model was built using the method of two-phase homogeneous flow developed in previous work, while the drift-flux approach for void fraction and profile-fit model for subcooled boiling were implemented. Although the rolling condition was chosen as the typical motion in this work, the additional force caused by the motion with six degrees of freedom was derived. The theoretical analysis was performed based on the method of small power perturbation for parallel-twin rectangular channels. The flow oscillation caused by rolling was studied for different system parameters, including inlet resistance, exit resistance, pressure, and axial heating profile. The influence on flow instability of rolling parameters such as period, amplitude, and distance between channels was analyzed. The results showed that it would destabilize the system if a larger additional force was generated by rolling parameters. The influence of different axial heat profiles on flow instability was also studied under inlet-peaked, cosine-shape, and outlet-peaked heat fluxes. The coupling effect of rolling motion and axial nonuniform heating was finally studied. The stability boundaries under different conditions were compared to the inherent boundary under the static condition with uniform heating. The results indicated that the influence of nonuniform heating was more evident and should be paid more attention to.

Natural convection heat transfer and entropy generation in a porous rhombic enclosure: influence of non-uniform heating

In this paper, we present a numerical investigation of natural convection heat transfer and entropy generation for a rhombic enclosure with inclination angle, ϕ = 30°, filled with a porous medium. The left and right surface walls of the enclosure are confined to cold temperature bath while we impart non-uniform, varying temperature distribution with unequal phase angles along the top and bottom wall. The flow inside the enclosure is steady, two-dimensional, incompressible and laminar, and the working fluid is air (Pr = 0.71). Numerical experiments have been performed using finite element method-based software COMSOL Multiphysics 5a for Darcy number and Rayleigh number in the extent of 10−4–10−2 and 103–106, respectively, in addition to phase deviation angles varying in the range from 0 to π. The amplitude parameter associated with the temperature delineation of the bottom and top walls is kept constant. The realizations from the numerical investigation are exhibited by streamlines and isotherms, local and average heat transfer Nusselt number along with the local distribution of heat transfer and fluid friction irreversibilities. The rate of heat transfer demonstrates non-monotonic trends and can be considerably influenced by the interplay of the phase shift angle, Rayleigh number and Darcy number. Upon increasing the value of phase shift angle from 0 to π, average Nusselt number initially decreases and thereafter shows an increase in its value. As the Darcy number increases, average Nusselt number for the bottom wall increases, while for the top wall it strongly depends on phase shift angle. In terms of entropy generation, it is found that the significant contributor to irreversibility is induced by heat transfer and the location of maximum entropy varies with the change in phase angle. More specifically, minimum entropy generation for any value of Rayleigh number and Darcy number is obtained for a phase shift angle of π/4 and maximum for 3π/4. The concomitant transport characteristics bear significance from the context of design of thermal systems pertaining to the theme of non-uniform heating with the phase angle being a crucial design parameter.

Influence of non-uniform heat source/sink and variable viscosity on mixed convection flow of third grade nanofluid over an inclined stretched Riga plate

The present study focuses on the impact of non-uniform heat source/sink and temperature dependent viscosity modeled by Reynolds on Cattaneo-Christov heat flow of third grade nanofluid subject to an inclined stretched Riga plate. Fourth order R-K and shooting methods have been implemented to obtain the numerical solution of the transformed boundary layer equations. The achievability of the present study is that the material constants associated with third grade fluid augment the fluid motion and boils down the fluid temperature leading to ascending velocity boundary layer and descending thermal boundary layer. And viscosity parameter enhances the heat transfer rate from the plate. Furthermore, augmented space and temperature dependent heat source upsurges the fluid temperature and the related thermal boundary layer thickness.

The influence of non-uniform heating on two-phase flow instability in subchannel

Two-phase flow instability is a very common phenomenon in two-phase systems, such as steam generator, BWR, boiler, condenser and so on. Normally, flow instability is not allowed to appear in the systems because it might result in potential issues such as thermal fatigue damage, mechanical vibrations, problems with system control as well as changing of heat transfer characteristics which may cause a boiling crisis. A lot of studies were presented on this subject based on uniform heating. However, non-uniform heating is the biggest characteristic in nuclear reactors which is different from most of the uniform heating systems. It is necessary to conduct research concerning non-uniform heating effect on two-phase flow instability for the reactor safety.This paper studies the flow instability in subchannels. The validation of subchannel model is performed using data from a GE 3 × 3 rod bundle test. The effects of peak value of power factor, peak location, and power curve shape along axial direction are examined. The stability comparisons based on stability boundaries are plotted with the phase change numbers versus subcooling numbers. The increase of peak value makes the system more stable when peak is at the downstream half of the test section and makes the system more unstable when peak is at the upstream side of the test section closer to the inlet. With power peak moves from inlet to outlet, the stability increases first and then levels off. With the increase of power shape factor F, which is the standard deviation of power curve data used to reflect power shape effect, stability increases when power peak is close to the exit and decreases when power peak is near the inlet of the test section. The radial non-uniform heating effect is not obvious in subchannel. According to the results of this stability study, recommendation is made on how to avoid conditions where two-phase flow instability easily occurs.

Nonuniform Heat Effects on Buckling of Laminated Composite Beam: Experimental Investigations

The influence of nonuniform heating on the critical buckling temperature of laminated glass-epoxy composite beam has been investigated experimentally with the help of a novel experimental setup. The beam is numerically investigated using nonlinear finite element analysis. An initial geometric imperfection is introduced to the modeled geometry in numerical technique to have an experimental–numerical comparison of temperature-deflection plot. The results indicate that the critical buckling temperature of a uniformly heated beam has a significant difference in comparison to the nonuniformly heated beam and it depends on the heating source location and the resulting temperature distribution along the length direction of the beam.

Influence of Non-Uniform Heat Source/Sink on Unsteady Chemically Reacting Nanofluid Flow over a Cone and Plate

This computational study explores the properties of non-uniform heat source/sink on the fluid transport properties of a chemically reacting nanofluid with two types of geometries saturated with porous medium. Simulations have been done to investigate the heat and mass transfer characteristics using Crank-Nicolson scheme. Influence of active parameters such as Hartman number, heat source and sinks, Brownian diffusion, higher order chemical reaction, Prandtl number and thermophoretic diffusivity are graphically presented. Tables demonstrate the significant impact of sundry parameters on skin-friction factor, heat and mass transfer rates. The achieved results expose that the heat source/sink parameter has high influences on the fluid flow and heat transfer characteristics. A decrease in average skin friction factor due to the magnetic field is more significant in the flow on a plate than that of cone.

Unsteady Magnetohydrodynamic Flow Past a Slendering Stretching Surface with Thermophoresis and Brownian Motion

In this paper, we investigate the influence of non uniform heat source/sink and thermal radiation on magnetohydrodynamic flow past a slendering surface with the influence of thermophoresis and Brownian effects. The governing non-linear flow problem is solved numerically by the aid of RK based shooting method. Influence of dimensionless parameters on the velocity, temperature and concentration profiles are explored through graphical illustrations. Skin friction factor, Nusselt and Sherwood numbers are presented and discussed. Rising values of magnetic and thermophoresis parameters increase the thermal and concentration distributions. Boosting values of Brownian motion parameter enhance the Nusselt and Sherwood numbers.

Dual solutions for heat and mass transfer in chemically reacting radiative non-Newtonian fluid with aligned magnetic field

Through this paper we investigated the heat and mass transfer in chemically reacting radiative Casson fluid flow over a slandering/flat stretching sheet in a slip flow regime with aligned magnetic field. This study is carried out under the influence of non uniform heat source/sink. First we converted the governing equations of the flow into ordinary differential equations by making use of suitable similarity transformations. The obtained non-linear differential equations are solved numerically using Runge-Kutta based shooting technique. Further, graphical representation has been given to study the effects of various physical parameters on velocity, temperature and concentration fields. Also numerical computations has been carried out to investigate the influence of the physical parameters involved in the flow on skin friction, rate of heat and mass transfer coefficients. Through this investigation, it is observed that aligned angle, Casson parameter and velocity slip parameter have the tendency to control the velocity field. Also heat transfer rate in flat stretching sheet is higher than that of slendering stretching sheet. A good agreement of the present results with the existed literature has been observed.

Buckling of non-uniformly heated isotropic beam: Experimental and theoretical investigations

Influence of non-uniform heating on critical buckling temperature of an aluminium beam has been investigated experimentally with the help of a novel experimental set-up developed in-house. Non-linear finite element analysis, considering the initial geometric imperfection, has been carried out to compare the experimentally obtained typical load-deflection curve. The linear critical buckling temperature predicted numerically are validated with analytical solutions. Experimental results revealed that critical buckling temperature of the non-uniformly heated beam greatly differs from the uniformly heated beam. It is also observed that the location of heat source and resulting non-uniform temperature variation influences the critical buckling temperature significantly.

Gapped smoothing algorithm applied to defect identification using pulsed thermography

On the basis of pulsed thermography, this article presents the development of a quantitative detection method for sub-surface defects. A two dimensional gapped smoothing algorithm (GSA) applied in this method to process the surface thermal distribution and no reference information is needed. A new thermal contrast is defined and a damage index based on the thermal contrast is proposed to estimate the probability of location of a defect, and differential curves of thermal contrast are applied for further quantification of defect size. One aluminium plate and one glass fibre reinforced composite laminate containing different depths of flat-bottom holes, delaminations and impurities are introduced to assess the performance of proposed method. Numerical and experimental results indicate that the influence of non-uniform heating is clearly suppressed. Compared with the differentiated absolute contrast approach, distinct enhancement of thermal contrast is achieved, and the location and size of sub-surface instances of damage can be quantitatively determined using the proposed method. The relation of damage index and flaw depth is investigated and a general expression is presented for the evaluation of flaw depth. The influence of the distribution density of the gapped grid on detection accuracy is further discussed. The proposed method, which is less dependent on the capture time, can be used for automatic detection and characterisation of defects. The reliability and applicability of the GSA applied to pulsed thermography are verified.

Influence of the Spatial Temperature Distribution in Coal Particles on Their Heating and Ignition in a Gas-Dispersed Flow

The influence of nonuniform heating of dry and moisture-saturated coal particles on the time and character of their ignition has been analyzed. The kinetic model of heterogeneous reactions on the particle surface and the equilibrium model of reactions in a gas phase are used. It is shown that a change in the temperature inside a moisture-containing particle can diminish (two and more times) the time of its ignition as compared to an isothermal particle.

Influence of non-uniform heating on the stresses in tubes of superheaters in boilers

The paper contents the results of temperature and stress field calculations occurring in the cross-section of first tube of the platen superheater P3 in the boiler BP 1150 (steam capacity 1150t/h). The non-uniform heat flux distribution resulting from radiation (from flue gas in the superheater as well as from the furnace) and convection has been taken into account. Calculations have been carried out for two coals, with lower and higher heating value.

Influence of nonuniform heating on the stability of plates beyond the elastic limit

Influence of nonuniform heating on the stability of plates beyond the elastic limit

Influence of nonuniform heating on the stability of cylindrical shells

Influence of nonuniform heating on the stability of cylindrical shells

The influence of non-uniform heating on the stability of a compressed bar

The influence of non-uniform heating on the stability of a compressed bar