Decrease In Heat Transfer Rate Research Articles

Flow characteristics of Au-blood nanofluid in stenotic artery

This article discussed the flow characteristics of human blood under stenoses assumptions. The human blood is considered as Newtonian fluid. The problem governing equations along with the boundary conditions are reduced to dimensionless form by using appropriate similarity transformation to obtain the numerical solution of velocity and temperature of blood flow through stenosed artery. The flow quantities are calculated at cylindrical surface and results are also shown through graphs and tables. Gold nanoparticles can improve the flow of blood and could be a promising therapeutic approach against arterial diseases as compared to Cu and Al2O3-NPs. Results shows that velocity and temperature of blood decreases by increasing the size of gold nanoparticles. Additionally, the skin friction and heat transfer analysis for the blood flow dynamics is also examined. It is noticed that by increasing the values of flow parameter, heat transfer rate and skin friction coefficient decreases. To predict the reason of the atherosclerosis, the modeling and numerical solution plays an incredible role.

Numerical study of thermal and mass enhancement in the flow of Carreau-Yasuda fluid with hybrid nanoparticles

Shear rate-pendent viscosity model has been used for the prediction of behaviour regarding shear thinning. Carreau-Yasuda model is one of them which predict shear thinning behaviour. The dynamics of fluid flow models are predicted numerically using shear rate-dependent model associated with Carreau and Yasuda. The two-dimensional heat transfer enhancement via hybrid nano-structures is investigated numerically. The outcomes of pure Carreau-Yasuda and Carreau-Yasuda fluid with nano-structures are compared. The FEM tool is used for numerical simulations and outcomes are recorded in the form of graphs and numerical data. It is observed during numerical experiments that wall shear stress in both types of fluids is proportional to the intensity of the magnetic field. Therefore, the rate of heat transport is decreased when Ohmic dissipations increase the temperature. of fluid. However, this decrease in heat transfer rate is more prominent in hybrid nanofluid relative to the mono nanofluid. The behaviour of generative chemical reactions on the concentration profile is opposite to the behaviour of destructive chemical reactions. It is noted that the motion of fluid has an increasing tendency when the Weissenberg number is increased. This impact of the movement of solid boundary in hybrid nanofluid is faster than the diffusion of wall movement in a mono nanofluid. The Rayleigh convection parameter tends to slow down the motion of molecules of mono nano and hybrid nanofluid. Shear stress increases when the intensity of the magnetic field is increased. This wall shear stress for MHD fluid is greater than that for fluid in absence of a magnetic field. The impact of change of intensity of magnetic field on temperature profiles. It is observed that magnetic force is a retarding force and causes retardation to flow. It means that convective transport of heat energy is compromised when the intensity of the magnetic field is increased.

Numerical Solution of Laminar Flow and Heat Transfer over a Flat Plate in a Nonuniform Stream.(Dept.M)

The laminar flow and heat transfer over an isothermal flat plate in a free stream with nonuniform velocity have been analysed, fully implicit numerical method (with a hybrid representation for the convective term normal to the streamwise direction) is used for solving the governing equations. Two practical cases are considered. In the first case, a flat plate is located in the laminar wake of an upstream plate. In the second case, a flat plate 18 inserted in the laminar shear layer joining a uniform stream and a quiescent fluid. The dependence of the boundary-layer and heat transfer on the lateral and the downstream shifts of the plate have been investigated. It was found that the nonuniformity of the free stream velocity causes reductions in both the wall shear stress and heat transfer relative to the corresponding values for uniform free stream. These relative reductions decrease with increasing downstream distance along the plate in the upper half of the wake. In the lower half of the wake, these Zeductions increase with distance along the plate. It was also found that the minimum values for drag and overall heat transfer rate at a certain streamwise location correspond to a slight downward shift of the plate from the wake centreline. In the case of shear layer, the relative reductions in the wall shear and heat transfer are more pronounced in the low velocity region. These reductions decrease with increasing downstream distance along the plate. It was found that both the drag and overall heat transfer rate decrease continuously with downstream shift of the plate.

Effects of Chemical Reaction, Activation Energy and Thermal Energy on Magnetohydrodynamics Maxwell Fluid Flow in Rotating Frame

The purpose of this research is to see how chemical processes, activation energy, and heat radiation affect MHD flow of Maxwell fluid in a rotating frame. Using applicable similarity transformations, the partial differential equations that regulate the flow are reduced to extremely nonlinear ordinary differential equations. Graphs and tables are used to study the impact of monitoring parameters on velocity, temperature, concentration profiles, reduced Nusselt number, reduced Sherwood numbers, and skin friction coefficients. Outstanding agreement is obtained when the present findings of the study is compared with the previous related research works. In the study, it is noted that an increase of the thermal radiation parameters contributes to an increase of the flow temperature region. When a fluid is subjected to a greater rotation parameter, the thermal boundary layer thickens and the heat transfer rate decrease. Moreover, a decline of mass transfer rate is observed for a rise of Prandl number, rotational parameter or Deborah number.

NUMERICAL STUDY OF NATURAL CONVECTIVE HEAT TRANSFER WITHIN M-SHAPED ROOFS

Natural convective heat transfer in M-shaped roofs has been investigated using CFD approach with the aim of determining the flowfield and thermal characteristics of the attic when heated through the ceiling for pitch angles 14o, 20o, 25o and 35o and Rayleigh number between 106 and 107. The results show that the ‘M’ shape of the roof has strong influence on the airflow pattern and heat transfer. For all the roof pitches, counterrotating cells with varying intensities and thermal plumes are obtained. The air velocity variation laterally across the attic forms a sequence that mimics the flowfield thus enabling the relative size of a cell and its intensity at a position in an attic of a particular pitch to be predicted. The size of the twin vortices at the central area is found to increase by 4% with the roof pitch. As the pitch increases, the thermal plumes get thicker while their number reduces and heat transfer rate decreases.

Laminar free convection from an elliptic tube placed in a Microplar fluid with vertical plate as a special case.(Dept.M)

In this paper laminar free convection heat transfer from a horizontal isothermal elliptic tube placed in a micropolar fluid with its major axis vertical is investigated. The governing equations basd on the conservation of mass, linear momentum, angular momentum and energey are numerically solved using the Fourier Spectral method. The main controlling parameters, beside the material parameters of the micropolar fluid, are the Rayleigh number, the Prandil number and the elliptic section axis ratio The micropolar fluid parameters are the vortex Viscosity, micro-inertia density and Spin gradient viscosity The results, which were obtained for a range of these parameters, were carried Out. at two axis ratios of 0.5 and 0.025. The axis ratio of 0.025 approximates the geometry of the special case of vertical flat plate. The results for vertical plate placed in Newtonian fluid arc compared with the relevant results in the literature and very good agreement was obtained. The study has shown that the vortex viscosity is the frost influencing material parameter on heat transfer rate. The study showed that as the vortex viscosity increases the heat transfer rate decreases.

The Effects of Internal Heat Generation or Absorption on Mixed Convection in a Lid-Driven Rectangular Cavity using Finite Volume Method

Mixed convection heat transfer in cavities is a significant phenomenon in numerous engineering fields, such as nuclear reactors, solar energy storage, and heat exchangers. Despite acknowledging that a square is a basic shape found in these systems, not all the figures are geometrical. Less attention was given to the rectangle cavity even though it could be found in these systems. Various internal reactions could occur inside the systems, especially in geothermal heat exchangers. Therefore, this research aims to analyze the effect of internal heat generation or absorption in a two-dimensional (2D) horizontal cavity to the fluid flow and heat transfer process numerically. The vertical walls are well insulated. Meanwhile, the top and bottom walls are kept at and , respectively, where . The top wall moves at a constant speed from left to right. The finite volume method (FEM) and SIMPLE algorithm are employed to discretize the governing equations. Next, the algebraic equations are solved iteratively using the tri-diagonal matrix algorithm (TDMA). The influences of heat generation or absorption parameters are investigated in terms of the flow, heat transfer, and Nusselt number. The numerical results are plotted in the form of streamlines and isotherms. It is found that the presence of heat generation or absorption has a significant effect on the fluid flow and heat transfer process in the horizontal cavity. Overall, for internal heat generation, the heat transfer rate decreases, while the opposite pattern can be observed for the case of internal heat absorption. However, for Ri = 10.0, as the heat generation's value increases from 2 to 4, the heat transfer rate is the same.

Direct numerical simulation of turbulent particle-laden flows: effects of Prandtl and Stokes numbers

The effect of molecular Prandtl number on the turbulent heat transfer of a non-isothermal turbulent channel flow laden with particles with four different Stokes number is investigated using direct numerical simulation coupled with a Lagrangian particle tracking. The flow configuration is a downward vertical channel with side walls kept at constant temperature. A total of 16 test cases with four different Prandtl numbers of Pr = 0.71, 1, 3, 7, and four particle sizes with the Stokes numbers of St= 40, 60, 100, 190 are considered. The mass loading, particle-to-fluid density ratio, and specific heat ratio are constant for all cases and they are equal to 0.57, 7298, and 0.39, respectively. It is shown that by the addition of particles, the heat transfer rate decreases and the thickness of the conductive sublayer thickness increases for all cases. The percentage of heat transfer modulation resulting from the addition of particles is almost independent of the Prandtl number but it slightly depends on the size of the particles, with the maximum being for smaller particles. The mean and rms values of temperature, temperature-velocity correlations, mean energy equation, and temperature variance budgets are presented. Contours of temperature in planes parallel to the wall and normal to the streamwise direction are also reported. At higher Prandtl numbers, the temperature contours clearly visualize the mushroom shaped structures formed as a result of the ejection of low-speed fluid from the wall.

Nanofluid flow and heat transfer of carbon nanotube and graphene platelette nanofluids in entrance region of microchannels

Suspensions of nano-scale particles in liquids, dubbed nanofluids, are of great interest for heat transfer applications. Nanofluids potentially offer superior thermal conductivity to alternative, pure fluids and are of particular interest in applications where active cooling of power-dense systems is required. In this work, the thermophysical properties of carbon nanotube nanofluids (CNTNf) and those of graphene nanoplatelette nanofluids (GNPNf) as functions of particle volume fraction are deduced from published experiments. These properties are applied to a perturbative boundary layer model to examine how the velocity and temperature profiles (and correspondingly shear stress and surface heat transfer) vary with the nanoparticle concentration in the entrance region of microchannels. Findings of this modeling effort indicate that both shear stress and heat transfer in GNPNf increase with increasing particle concentration. The normalized increase in shear stress is approximately twice that for heat transfer as a function of the GNP particle concentration. Interestingly, CNTNf shows anti-enhancement heat transfer behaviour; an increasing concentration of CNT nanoparticles is associated with both an increase in shear stress and a decrease in the surface heat transfer rate.

A Weibull Distribution: Flow and Heat Transfer of Nanofluids Containing Carbon Nanotubes with Radiation and Velocity Slip Effects

In this study, the Tiwari and Das model is numerically studied, in case of a moving plate containing both single-walled and multiwalled carbon nanotubes (SWCNTs and MWCNTs, respectively), in the presence of thermal radiation and the slip effect. Employing the similarity transformation, a set of 2nd-order partial differential equations (which are used to model the flow and heat transfer) are solved numerically using the boundary value problem with 4th-order accuracy (BVP4C) method. The effects of related parameters, such as the volume fraction of nanoparticles, moving, slip, and radiation parameter on the heat transfer performance are analysed and discussed. Results indicate that a unique solution was placed when the plate travels in assisting flow conditions. Additionally, as the nanoparticle volume fraction (φ) rises at φ = 0.2, the skin friction and heat transfer rate decrease. It is also observed that when the slip parameter (β) increases at β = 0.4, the skin friction decreases, whereas the heat transfer rate increases. Meanwhile, the heat transfer rate decreases when the thermal radiation (NR) increases to 0.7. Moreover, it is found that the SWCNTs are more efficient when the skin friction coefficient and the Nusselt number are considered. It is found that the Weibull distribution is more suitable in fitting the skin friction data.

Magnetohydrodynamic and Heat Transfer Impacts on Ferrofluid Over a Rotating Disk: An Application to Hard Disk Drives

Abstract The motivation behind this article is to explore the impacts of heat transfer, magnetohydrodynamic, and hall current on two-dimensional incompressible nanofluid flow over a rotating disk. The nanofluid model utilized in the present investigation comprises the nanoparticle fraction model. Two sorts of nanoparticles to be specific Hematite (Fe2O3) is the principal source of iron and Cobalt alloy (Co64 Cr30 W6) is generally used metal alloy that is primarily Cobalt and Chromium with base fluid Motor Oil 10W30 is taken into consideration. The Prandtl number identifying with motor oil is (Pr = 1531.92). The governing equations are reduced to a system of ordinary differential equations by using Von-Karman transformation and then solved numerically utilizing matlab bvp4c. Impacts of the magnetic field, hall current, and nanoparticle volume fraction on tangential, radial velocities, and temperature profiles have been examined. Numerical outcomes have been acquired for various physical parameters through graphical representation. We have demonstrated that a remarkable reconciliation exists among the current outcomes and those in the literature for various values of magnetic parameter and velocity slip parameters, in the absence of other parameters. It is also found that radial and tangential velocities increase more in the case of Fe2O3 nanoparticles when compared with Co64 Cr30 W6 because of density variations. It is discovered that enhancement in a nanoparticle volume fraction reduces the heat transfer rate. It can moreover be clarified such a way that as the nanoparticle volume fraction raise, the density of nanoparticles increases, temperature also increases subsequently heat transfer rate decreases. This result keeps more cooling for the hard disk drives and might be intrigued for engineers.

Conduction Heat Rate Analysis of Tool in AISI 4340 TurningProcess

In the turning process a very high temperature is generated from the friction of cutting tool and workpiece. In the turning process there is also contain heat transfer reaction that occurs due to rising temperatures during the turning process. The high temperature in the cutting process has a very important influence on increasing the amount of heat that produce during the process of machining. Therefore it is necessary to analyze the effect of the rake angle and the use of LN2 and SCCO2 as a cooler to the heat transfer rate on the cutting tool using Autodesk simulation mechanical 2017 software. Based on the simulation results obtained temperature distribution values on the cutting tool during the AISI 4340 turning process using carbide tungsten as the cutting tool where the rake angle is 0°,5°, and 10°. Without using any coolant, the heat transfer rates are 30.613W, 28.386 W, and 26.160. By applying cooler such as SCCO2 and LN2 the rate of heat transfer decreases. With the application of the LN2 heat flow rate with rake angle 0°, 5°, and 10° decrease to 21.429 W, 19.191 W, and 16.965 W. The application of the SCCO2 heat flow rate on the tool with a rake angle 0°, 5°, and 10° will be 20.260 W, 18.479 W, and 16.252 W. Based on the result it is found that increased rake angle will cause a decrease in heat transfer rate. The application of SCCO2 and LN2 can reduce the heat transfer rate, therefore it can extend the cutting tool life.

Effects of surface roughness on mixed convective nanofluid flow past an exponentially stretching permeable surface

A numerical study is carried out to display the effects of surface roughness on mixed convective nanofluid flow along an exponentially stretching surface in presence of suction/injection. The dimensional coupled nonlinear partial differential equations are transformed into dimensionless form by using suitable non-similar transformations. The resulting equations are solved by utilizing the Quasilinearization technique as well as the implicit finite difference scheme. The influence of several non-dimensional parameters on various profiles and gradients is examined. The results are presented graphically, which are analyzed to depict the effects of various physical parameters, for example, Brownian diffusion parameter Nb, thermophoresis parameter Nt, suction/blowing parameter A and Lewis number Le. In order to analyse the influence of surface roughness on mixed convective nanofluid flow, the major part of this research paper is devoted to investigate the effects of the small parameter α and frequency parameter n over the gradients defined at the wall. The results reveal that an increase in the values of Nb and Nt, enhances the velocity and temperature of the fluid. The increasing value of suction parameter (A > 0) reduces the velocity of the fluid. Further, the increasing values of Nb and Le decrease the nanoparticle volume fraction profile. The sinusoidal variations are observed in the skin-friction coefficient, Nusselt number as well as the nanoparticle Sherwood number. Moreover, with the addition of nanoparticles, the magnitude of the skin-friction coefficient increases, while the magnitude of heat transfer rate decreases, significantly.

Performance analysis of different transverse and axial micro-fins in a turbulent-flow channel

Turbulent-flow and heat-transfer characteristics have been numerically studied in a turbulent channel flow with different micro-fin roughnesses on the lower wall. Internally enhanced surfaces such as micro-fins are beneficial to thermal performance in commercial applications such as heat exchangers, refrigerators, chillers, and air conditioners. In contrast, the added mass of the fins to the surface leads to higher costs for bulk commercial products and also increases pressure drop. Studies of flow fields around these fins have appeared in the literature but often do not include conduction analysis in the fin, leaving a key optimization parameter unexplored. The goal of this paper is to fill this gap by finding out the effects of micro-fin design parameters on heat-transfer enhancement and pressure drop by holding the micro-fin volume constant over the numerical space. Design parameters of interest are cross-sectional profile, height, yaw angle, and pitch. A coupled numerical simulation of the turbulent flow at Reynolds number 15,000, with periodic boundaries and solid domains, was set up and validated in ANSYS Fluent and the performance was mapped. Mean-velocity profiles showed the well-known downward shift of the logarithmic portion of the law of the wall. Results showed the transverse rectangular micro-fin with pitch-to-height ratio (p/Ks) of 3.5 (corresponds to a so called d-type roughness) can enhance the performance factor by as much as 40% compared with a smooth surface. In addition, by changing the micro-fin pitch, it was found that the heat-transfer rate decreases and pressure drop increases for the transverse rectangular micro-fins with p/Ks of greater than 5 (corresponds to a k-type roughness), which demonstrated the breakdown of the Reynolds analogy.

Cost Benefit Analysis Of Window Air Conditioning System with Evaporative Cooled Condenser

This paper shows performance analysis of the possibility of augmentation of Coefficient of Performance and reduced power consumption of a window air conditioning trainer using an evaporatively cooled condenser. In general, during the dry and hot season, performances of without evaporative cooling condenser minimize, and Coefficient of Performance decreases because of condenser heat transfer rate decreases. This hypothesis has been tested by setting an experimental set up of a window air conditioning trainer using evaporative cooling for condensation. The results show a considerable enhancement of Coefficient of Performance of with evaporative cooling condenser as compared to without evaporative cooling condenser. The test however also shows the applicability of evaporative cooling only during the torrid atmospheric conditions.

Numerical simulation of water/alumina nanofluid mixed convection in square lid-driven cavity

PurposeThe purpose of this paper is to investigate the mixed convection of a two-phase water–aluminum oxide nanofluid in a cavity under a uniform magnetic field.Design/methodology/approachThe upper wall of the cavity is cold and the lower wall is warm. The effects of different values of Richardson number, Hartmann number, cavitation length and solid nanoparticles concentration on the flow and temperature field and heat transfer rate were evaluated. In this paper, the heat flux was assumed to be constant of 10 (W/m2) and the Reynolds number was assumed to be constant of 300 and the Hartmann number and the volume fraction of solid nanoparticles varied from 0 to 60 and 0 to 0.06, respectively. The Richardson number was considered to be 0.1, 1 and 5. Aspect ratios were 1, 1.5 and 2.FindingsComparison of the results of this paper with the results of the numerical and experimental studies of other researchers showed a good correlation. The results were presented in the form of velocity and temperature profiles, stream and isotherm lines and Nusselt numbers. The results showed that by increasing the Hartmann number, the heat transfer rate decreases. An increase from 0 to 20 in Hartmann number results in a 20 per cent decrease in Nusselt numbers, and by increasing the Hartmann number from 20 to 40, a 16 per cent decrease is observed in Nusselt number. Accordingly, it is inferred that by increasing the Hartmann number, the reduction in the Nusselt number is decreased. As the Richardson number increased, the heat transfer rate and, consequently, the Nusselt number increased. Therefore, an increase in the Richardson number results in an increase of the Nusselt number, that is, an increase in Richardson number from 0.1 to 1 and from 1 to 5 results in 37 and 47 per cent increase in Nusselt number, respectively.Originality/valueEven though there have been numerous investigations conducted on convection in cavities under various configurations and boundary conditions, relatively few studies are conducted for the case of nanofluid mixed convection in square lid-driven cavity under the effect of magnetic field using two-phase model.

Anomalous diffusion in rotating Casson fluid through a porous medium

This paper investigates the space-fractional anomalous diffusion in unsteady Casson fluid through a porous medium, based on an uncoupled continuous time random walk. The influences of binary chemical reaction and activation energy between two horizontal rotating parallel plates are taken into account. The governing equations of motion are reduced to a set of nonlinear differential equations by time derivatives discretization and generalized transformation, which are solved by bvp4c and implicit finite difference method (IFDM). Stability and convergence of IFDM are proved and some numerical comparisons to the previous study are presented with excellent agreement. The effects of involved physical parameters such as fractional derivative parameter, rotation parameter and time parameter are presented and analyzed through graphs. Results indicate that the increase of fractional derivative parameter triggers concentration increase near the lower plate, while it causes a reduction near the upper plate. It is worth mentioning that the decrease of heat transfer rate on the plate is observed with the higher time parameter.

Slip role for unsteady MHD mixed convection of nanofluid over stretching sheet with thermal radiation and electric field

This paper mainly focuses on the impacts of slip conditions on the two-dimensional unsteady mixed convection flow of electrical magnetohydrodynamic nanofluid over a stretching sheet in the presence of thermal radiation, viscous dissipation, and chemical reaction. The synchronized impacts of electric and magnetic fields on the momentum and energy fields using Buongiorno nanofluid model were introduced to enhance thermal conductivity and hence create more pathways to heat transfer performance of nanofluid. The highly nonlinear couple systems of partial differential equations were modeled as a set of nonlinear ordinary differential equations by using suitably defined transformations which are then solved by implicit finite difference scheme known as Keller box method. It was established that velocity has a direct opposite relationship with electric and magnetic fields. The velocity, temperature, and concentration profiles caused intense decay to velocity slip, thermal slip, and solutal slip, with permeability condition. Magnetic field enhances the nanofluid temperature intensely with impermeable medium resulting in a decrease in heat transfer rate from the surface. The heat convection current is strengthened by viscous dissipation and radiative heat transfer prevailing impermeability, which leads to a reduction in heat transfer rate. Comparisons with previously published works seen in the literature were made, and the result was found to be in excellent agreement.

Hematocrit and Slip Velocity Influence on Third Grade Blood Flow and Heat Transfer through a Stenosed Artery

A theoretical investigation concerning hematocrit and slip velocity influence on the flow of blood and heat transfer by taking into account the externally applied magnetic field has been carried out. The mathematical models considered in this work treated blood as a non-Newtonian fluid obeying the third grade fluid model. A suitable geometry of the stenosis is taken into account. Galerkin weighted residual and Newton Raphson methods are used to solve the equations that govern the flow of blood and heat transfer. Analytical expression for the velocity profile, temperature profile, volume flow rate, wall shear stress and resistance to flow were obtained. Graphical representation of results shows that the flow velocity, volumetric flow rate and shear stress increase while resistance to flow and heat transfer rate decrease when the slip velocity increases. Also, flow velocity and volume flow rate decrease while shear stress, heat transfer rate, and resistance to flow increase when the hematocrit parameter increases. Finally, increases in magnetic field parameter lead to decrease in flow velocity, flow rate and shear stress but increase the flow resistance.

Hydrothermal analysis of Non-Newtonian second grade fluid flow on radiative stretching cylinder with Soret and Dufour effects

The present paper examines the analytical approach of a second grade fluid flow along a stretching cylinder and the Soret and Dufour effects is also investigated on the problem. The flow is subjected to thermal radiation. A system of non-linear equations has been extracted using the mathematical modeling of a second grade fluid flow in a cylindrical coordinate system. Homotopy analysis method (HAM) was implemented to solve this problem which an excellent agreement between this method and the numerical approach was observed in the results. The effect of the following physical parameters on the velocity, temperature and concentration profiles has been investigated in this paper; viscoelastic parameter (We), curvature parameter γ, Dufour parameter (Du), Soret parameter (Sr), temperature exponent (n), effective Prandtl number Preff and Schmidt number (Sc), etc. moreover, the drag coefficient on surface along with heat and mass transfer rate are also investigated and presented in various tables. For instance, it is predicted that Simultaneous variations of Du and Sr has an inverse relation for heat and mass transfer rate. In this case increasing Du and decreasing Sr would cause a decrease in heat transfer rate along with an increase in mass transfer rate.