Heat Transfer Aspects Research Articles

Heat Transfer Analysis of Micro Polar Fluid with AL2O3 and CuO Hybrid Nanofluid Over a Plate with and Without Out Viscous Dissipation

Abstract: This work analysis investigated with the boundary layer stream and heat transfer aspects of a micropolar nanofluid over a porous shrinking sheet with thermal radiation. The boundary layer equations governed by the partial differential equations are transformed in to a set of ordinary differential equations with the help of suitable local similarity transformations. The coupled nonlinear ordinary differential equations are solved by the commercial MATLAB code bvp4c.The solutions of dimensionless velocity ,velocity gradient and temperature profiles are analyzed by the effect of various controlling flow parameters nonlinear parameter ,material property and Eckert number. and temperature and Prandtl number. Physical quantities such as skin frication coefficient, local heat, computed. Keywords: Viscous effects .flat plate, Nanofluid, hybrid nanofluid, micro polar fluid , local Nusselt number, skin friction, micro rotation

Experimental Investigation on Heat Transfer Enhancement with Passive Inserts in Flat Tubes in due Consideration of an Efficiency Assessment

This paper presents results of an experimental investigation on pressure drop and heat transfer for a wide range of Reynolds and Prandtl numbers ranging from 8 < Pr < 60 and 40 < Re < 3500, for flat tubes without and with passive inserts. For three different kinds of passive insert designs, the impact on heat and momentum transfer due to coaction of the total set of passive inserts with different shape and amount was investigated. Experimental results were analyzed regarding two main aspects: Heat transfer mechanisms and pressure drop induced by friction and form drag forces due to the presence of different shapes. After heat and momentum transfer mechanisms for each passive insert design were analyzed, heat transfer and pressure drop enhancement were compared to each other, leading to an efficiency discussion. Different concepts for efficiency evaluation, which are cited in literature, were applied to the presented experimental data. Pros and cons of the different concepts are discussed. Finally, we propose an equation for evaluation of total performance, which fully respects the energetic and exergetic aspects of heat transfer and pressure drop enhancement.

EFFECT OF KEROSENE MASS FLOW RATE AND AVERAGE TEMPERATURE IN DIRECT CONTACT HEAT EXCHANGER

Industrial plants are huge consumers of energy, these plants are installing heat exchangers in an effort to reduce energy consumption, and so improve operating efficiencies. Limited numbers of experimental and numerical investigations have dealt with the parameters affecting the heat transfer aspects in single phase direct contact heat exchangers which may be selected for their high thermal efficiency and minimum capital investment. In oil refineries energy from hot temperature oil streams can be recovered by transfer directly to a cheap coolant liquid in liquid-liquid direct contact heat exchangers. The heat recovered from these heat exchangers has different applications including preheating boiler feed water and preheating wash water. Heat recovery from hot temperature refinery products using direct contact heat exchanger throughout a theoretical phenomenological study is central to the theme of this paper. Kerosene-water system has been chosen. The effect of the heating fluid inlet temperature (65-97.50)°C, and mass flow rate (25 to 45) kg/s on direct contact heat exchanger design parameters and heat transfer characteristics were investigated theoretically throughout nine cases. Correlations of heat recovered from the system as well as design and operating characteristics of the heat exchanger were estimated. Increasing kerosene flow rate found to associate directly with increasing the contact surface area, number of plates, number of channels per pass and pressure drop, while when the heat exchanger is designed to operates at high kerosene inlet temperature, big heat exchangers with large areas, high number of plates and channels per pass are needed for efficient heat exchanger performance. Optimization and modeling the effect of kerosene operating variables on heat recovered was conducted using Response Surface Methodology. The results showed that an optimum heat recovery value of 6.8782 megawatt could be achieved for kerosene optimum inlet temperature (91.82°C), and mass flow rate (50.11 kg/s). Keywords: direct contact heat exchanger; kerosene and water system, kerosene mass flow rate and inlet temperature.

Double Diffusive Magneto-Free-Convection Flow of Oldroyd-B Fluid over a Vertical Plate with Heat and Mass Flux

The purpose of this research is to analyze the general equations of double diffusive magneto-free convection in an Oldroyd-B fluid flow based on the fundamental symmetry that are presented in non-dimensional form and are applied to a moving heated vertical plate as the boundary layer flow up, with the existence of an external magnetic field that is either moving or fixed consistent with the plate. The thermal transport phenomenon in the presence of constant concentration, coupled with a first order chemical reaction under the exponential heating of the symmetry of fluid flow, is analyzed. The Laplace transform method is applied symmetrically to tackle the non-dimensional partial differential equations for velocity, mass and energy. The contribution of mass, thermal and mechanical components on the dynamics of fluid are presented and discussed independently. An interesting property regarding the behavior of the fluid velocity is found when the movement is observed in the magnetic intensity along with the plate. In that situation, the fluid velocity is not zero when it is far and away from the plate. Moreover, the heat transfer aspects, flow dynamics and their credence on the parameters are drawn out by graphical illustrations. Furthermore, some special cases for the movement of the plate are also studied.

Simultaneous laser-induced fluorescence, particle image velocimetry and infrared thermography for the investigation of the flow and heat transfer characteristics of nucleating vapour bubbles

Boiling is an effective heat removal process, used for heat exchange and thermal management purposes in many technological applications, from the scale of microelectronic devices to nuclear reactors. However, the physical mechanisms involved in this process are not fully understood yet due to the complexity that arises from the many interacting underlying sub-processes involved in the nucleation, growth and detachment of bubbles that occur during the process. Here, we present an advanced methodology based on combined, synchronized high-speed infrared (IR) thermometry, ratiometric two-colour laser-induced fluorescence (2cLIF) and particle image velocimetry (PIV), along with sample results of an experimental investigation conducted in deionized water, aimed at elucidating the mechanisms involved in the bubble lifecycle. IR thermometry is used to measure the time-dependent 2-D temperature and heat flux distributions over a boiling surface, and 2cLIF is used to measure the time-dependent temperature-field in a vertical plane, in the liquid phase around developing bubbles. Furthermore, PIV is used to measure the velocity fields around the bubbles, in the same plane as 2cLIF. The investigation reveals and allows us to quantify fundamental heat transfer aspects such as the contribution of triple contact line evaporation to the bubble growth process, the dynamics of the near-wall superheated liquid layer, the mixing effect produced by bubble growth and departure, convection effects around the bubble, and quenching heat transfer. Specifically, we observe that, in our experiment, with slowly growing bubbles, the microlayer does not form, and the evaporation at the solid-liquid-vapour contact line contributes to approximately one third of the total heat transferred to the bubble. We also observed that the fluid that rewets the dry spot at the bubble base, as the bubble departs from the boiling surface, comes from the near-wall superheated thermal boundary layer adjacent to the bubble, i.e., it is warmer than the fluid in the bulk. We confirm this finding by modelling this quenching heat transfer phase as a transient conduction process.

Numerical study of heat transfer aspects in cutting tools made of Al2O3, ZrB2, TiB2, TiN using ANSYS fluent software

In this study, the effects of heat transfer and heat flux on cutting tools with materials of Al2O3, ZrB2, TiB2, TiN are investigated numerically by ANSYS fluent software. The numerical model was validated with the previous study. The influence of the machining parameters such as cutting speed and feed rate on the temperature and tool life has been investigated to indicate the optimum cutting tool and situation. The results show that Zirconium diboride (ZrB2) and Titanium diboride (TiB2) have a temperature less than the aluminum oxide (Al2O3) so that the productivity will increase with the diboride materials utilizing as cutting tool. The maximum temperature for aluminum oxide is 1300 K while the Titanium Nitrite achieved 1100 K. The lowest and maximum temperature was measured at a cutting speed of 180 m/min and 220 m/min, respectively. The optimum cutting condition has been obtained with TiN cutting tool material at 180 m/min cutting speed and 0.138 mm/ rev feed rate. Titanium diboride (TiB2) materials achieved the maximum cutting tool life comparing to other materials.

Onset about non-isothermal flow of Williamson liquid over exponential surface by computing numerical simulation in perspective of Cattaneo Christov heat flux theory

In view of increaing significance of non-isothermal flow of non-Newtonian fluids over exponential surfaces in numerous industrial and technological procedures such as film condensation, extrusion of plastic sheets, crystal growth, cooling process of metallic sheets, design of chemical processing equipment and various heat exchangers, and glass and polymer industries current disquisition is addressed. For comprehensive examination Williamson model expressing the attributes of shear thickening and thinning liquids is taken under consideration. The physical aspects of magnetic field applied in transverse direction to flow is also accounted. Heat transfer aspects are incorporated and analyzed by employing Cattaneo-Christov heat flux model. Mathematical formulation of problem is conceded in the form of PDE’s by implementing boudary layer approach and later on converted into ODE’s with the assistance of transformation procedure. The resulting equations are solved numerically using shooting and Runge–Kutta methods. Impact of involved parameters on flow distributions is displayed through graphs. From the analysis it is inferred that Cattaneo Christov heat flux law exhibits hyperbolic equation which follows the causality principle and make the problem more compatible to real world applications. It is also deduced that magnetic field suppresses the velocity field and associated boundary layer region. Decrease in temperature profile and heat transfer coefficient is found against inciting magnitude of thermal relaxation parameter. Substantial decrease in velocity is found against increasing magnitude of Williamson fluid parameter and magnetic field parameter whereas skin friction coefficient increments. Confirmation about present findings is executed by making comparison with existing literature.

Features of Cu and TiO2 in the flow of engine oil subject to thermal jump conditions

The recent work investigates the heat transfer attributes in the flow of engine oil which comprises of nano-particles such as Cu and TiO2. The performance of Copper and Titanium oxide is over looked in the flow of engine oil. The energy equation is amended by the features of thermal radiation, viscous dissipation, and heat generation. The mathematical model signifies the porosity, entropy generation and moving flat horizontal surface with the non-uniform stretching velocity. Quasi-linearization, which is a persuasive numerical technique to solve the complex coupled differential equations, is used to acquire the numerical solution of the problem. Flow and heat transfer aspects of Cu–TiO2 in the flow are examined against the preeminent parameters. The flow is significantly affected by the thermal jump conditions and porous media. It is observed here that the temperature as well as heat transport rate is reduced with the effect of involved preeminent parameters. However, such fluids must be used with caution in applications where a control on the heat transfer is required. We may conclude that the recent study will provide assistance in thermal cooling systems such as engine and generator cooling, nuclear system cooling, aircraft refrigeration system, and so forth.

An experimental investigation on a novel direct-fired porous boiler for the low-pressure steam applications

Heat is the most essential form of energy for mankind lives. Steam is the most widely used as heat-carrying medium in the world. The boiler is the best system for the conversion of chemical energy contained in fuels into steam or hot fluid. According to the efficiency of all existing boilers, one of the most important factors that substantially affect this boiler performance index is the stack losses. This research proposed a novel direct-fired porous boiler (DPB). Because of it has no stack losses, this proposed boiler could outperforms all of the existing boilers. The purpose of this article is to discuss the potential of enhancing the suggested DPB performance by using different physical characteristics of packed-bed porous medium (PPM). The experimental results show that among the four most bed shapes available in the market and have a high heat transfer aspect, the hex-nut shape has been selected to use in the proposed DPB. At the heat input rate of about 14 kW, the steam generation rate of about 20 kg/h, (at 1.5 barg and 300 °C), is obtained. Because it has only surface heat loss, thermal efficiency of more than 98% can be achieved. It can be concluded that the possibility of using a hex-nut bed as a packed bed porous medium in a low-pressure porous boiler is confirmed with the proposed boiler.

Performance Evaluation of the Electric Machine Cooling System Employing Nanofluid as an Advanced Coolant

In this paper, the overall performance of an electric machine cooling system was examined in terms of heat transfer and fluid flow. The structure of the cooling system was based on the cooling jacket method. The cooling jacket contains spiral channels surrounding the stator and end-windings of the electric machine. Al2O3-water nanofluid is used inside the channels as the cooling fluid. The concentration of nanoparticles and the geometric structure of the cooling system have special effects on both aspects of heat transfer and fluid flow. Therefore, in this paper, the overall performance of the cooling system was evaluated by considering these effects. This study compared the importance of heat transfer and fluid flow performances on the overall performance of the cooling system. Numerical analyses were performed by 3D computational fluid dynamics and 3D fluid motion analysis. The analyses were carried out based on the 3D finite element method using the pressure-based solver of the Ansys Fluent software in steady mode.

Mathematical Modeling of Fluid Flow and Heat Transfer in Petroleum Industries and Geothermal Applications 2020

In this Special Issue, all aspects of fluid flow and heat transfer in geothermal applications, including the ground heat exchanger, conduction, and convection in porous media, are considered. The emphasis here is on mathematical and computational aspects of fluid flow in conventional and unconventional reservoirs, geothermal engineering, fluid flow and heat transfer in drilling engineering, and enhanced oil recovery (hydraulic fracturing, steam-assisted gravity drainage (SAGD), CO2 injection, etc.) applications.

Comparative study for magnetized flow of nanofluids between two parallel permeable stretching/shrinking surfaces

The current study intended to discuss a comparative study on the three dimensional Casson nanofluid with nonlinear radiative MHD flow and heat transfer aspects between two parallel stretching/shrinking surfaces. The mathematical models for momentum and temperature are established by employing the boundary layer flow of fluids with spinel-type ferrite MnFe2O4 nanoparticles being distributed in Pure Water/ (H2O) as the base fluid. Remarkable models like Maxwell-Garnett and Patel models are inserted in view of thermal conductivity augmentation. The suitable similarity transformations are adopted for converting the governing non-linear partial differential equations into non-dimensional ODE's and obtaining the relevant parameters for discussion. The major outers of the present study are axial velocity {F′(η)} peters out with amplifying β subject to stretched and shrunk surfaces in relation to both Maxwell-Garnett and Patel models. Growing θw and n exhibits opposite effect on heat transfer rate.

Study on heat transfer aspects of solar aircraft wings for the case of Reiner-Philippoff hybrid nanofluid past a parabolic trough: Keller box method

Solar energy is the major source of heat energy from the sun having immense utilization in technologies like photovoltaic cells, solar energy plates, solar street lights, solar water pumping, and so on. How to maximize the heat energy which is later on used as electrical energy for many purposes in solar aircraft is the hot topic of research in this decade. The current paper is about the study of entropy generation analysis and hybrid nano-solid particles impact on parabolic trough surface collector (PTSC) located inside the solar aircraft wings. homo/heterogeneous reactions have been taken. Non-Newtonian Reiner-Philippoff model along with porous medium and Darcy-Forchheimer effects have been taken into account for the present study. The heat transfer performance of the solar aircraft wings has been enhanced with the inclusion of effects like hybrid nanoparticles, thermal radiations, variable thermal conductivity, and viscous dissipation. By utilizing the proper conversions the demonstrated partial-differential equations are renovated into ordinary-differential formulas and tackled numerically with the utilization of well established numerical scheme termed as Keller-Box method. The impact of dimensionless sundry parameters on velocity, shear stress, temperature, homo/heterogeneous as well as surface drag and heat transfer rates are sketched through tables and figures. A positive variation in thermal radiation, thermal conductivity, and viscous dissipation effects enhances the heat transfer rate inside the solar aircraft wings.

Thermal analysis on uniformly heated diamond obstruction in convective liquid suspension

Heat transfer analysis of partially heated non-Newtonian liquid suspensions in closed enclosures rooted with the porous medium attracts the attention of researchers due to its abundant applications in thermal engineering. The problem appears at the solution exploration stage of the non-linear differential system constructed against heated liquid suspension equipped in a partially heated porous cavity. Therefore, the present numerical study is devoted to reporting the untapped characteristics of the non-Newtonian liquid suspension in a partially heated square enclosure rooted with diamond obstruction. The flow in a porous medium is induced by in-taking free convection. To encounter liquid suspension heat transfer aspects we have incorporated the energy equation. The enclosures lower wall is evenly heated, while the upper wall is held adiabatic. We used the finite element approach to solve the partial differential equations that resulted from the modeling. To bring hybrid meshing of the porous domain, both rectangular and triangular elements are selected. The free convection and porous media result in the Rayleigh number and Darcy number. We execute both contour and line graph studies to report the variation in Casson fluid stream function, Casson fluid temperature, pressure, dimensionless vertical velocity, horizontal velocity, and Nusselt number. It is concluded that installing Diamond-shaped obstruction in a porous medium result in heat transfer enhancement within a closed square cavity. The current theoretical research is intended to assist in the analysis of non-Newtonian fluid flow fields in heated porous enclosures.

Mixed convection and melting rheology in dual stratified Eyring-Powell nanofluid flow over surface of variable thickness: Buongiorno model approach

Eyring Powell fluid flow over linear as well as nonlinear stretching surfaces has been discussed in literature by several researchers. However, lesser attention has been paid for such studies with surfaces comprising variable thickness. Present communication inculcates the novel features regarding melting heat transport in Eyring Powell nanofluid over a surface of variable thickness while keeping in view the aspects of radiative heat transfer. Influence of thermophoresis and Brownian motion phenomena is discussed by making use of Buongiorno model approach. Here, the flow characteristics are analyzed in mixed convective and dual stratified porous medium. Appropriate transformations are imposed in order to convert partial differential equations to ordinary differential equations possessing highly nonlinear form. Homotopy analysis method is utilized to achieve desired convergent series solutions. Impact of several emerging variables on velocity temperature and concentration distributions is analyzed graphically. Expressions for drag force and rate of heat transfer are evaluated and demonstrated graphically. Nano particle concentration increases for higher Brownian motion parameter. Enriched thermal field is attained due to rise in thermophoretic parameter. However, recessive behavior of velocity profile results due to higher fluid parameters. Thermal field rises as a result of larger values of mixed convection parameter while it decays gradually for enhanced melting parameter.

Enhanced Heat Transfer by Oil/Multi-Walled Carbon Nano-Tubes Nanofluid

The subject of the study is mainly based on thermal reinforcement by an oily fluid containing nanometer particles of carbon. The study is carried out by the presence of discontinuous bars in two different shapes, i.e. flat and V, inside a horizontal heat exchanger. The study relies on simulations in thermal and dynamic terms from the literature. The turbulence effect is diagnosed by applying the k-ε model, while the flow hydrothermal transport relationships are modeled based on the finite volume technique. Both the flow and heat-transfer aspects of all channel regions are studied and analyzed. The new heat-exchanger structure has been enhanced in the presence of these discontinuous bars by reducing the friction coefficient and eliminating stations with poor transfer of heat behind these deflectors.

Non-similar mixed convection analysis for magnetic flow of second-grade nanofluid over a vertically stretching sheet

The aspiration of this research is to explore the impact of non-similar modeling for mixed convection in magnetized second-grade nanofluid flow. The flow is initiated by the stretching of a sheet at an exponential rate in the upward vertical direction. The buoyancy effects in terms of temperature and concentration differences are inserted in the -momentum equation. The aspects of heat and mass transfer are studied using dimensionless thermophoresis, Schmidt and Brownian motion parameters. The governing coupled partial differential system (PDEs) is remodeled into coupled non-similar nonlinear PDEs by introducing non-similar transformations. The numerical analysis for the dimensionless non-similar partial differential system is performed using a local non-similarity method via bvp4c. Finally, the quantitative effects of emerging dimensionless quantities on the non-dimensional velocity, temperature and mass concentration in the boundary layer are conferred graphically, and inferences are drawn that important quantities of interest are substantially affected by these parameters. It is concluded that non-similar modeling, in contrast to similar models, is more general and more accurate in convection studies in the presence of buoyancy effects for second-grade non-Newtonian fluids.

Convective heat transfer for Peristaltic flow of SWCNT inside a sinusoidal elliptic duct.

A mathematical model is presented to analyse the flow characteristics and heat transfer aspects of a heated Newtonian viscous fluid with single wall carbon nanotubes inside a vertical duct having elliptic cross section and sinusoidally fluctuating walls. Exact mathematical computations are performed to get temperature, velocity and pressure gradient expressions. A polynomial solution technique is utilized to obtain these mathematical solutions. Finally, these computational results are presented graphically and different characteristics of peristaltic flow phenomenon are examined in detail through these graphs. The velocity declines as the volume fraction of carbon nanotubes increases in the base fluid. Since the velocity of fluid is dependent on its temperature in this study case and temperature decreases with increasing volumetric fraction of carbon nanotubes. Thus velocity also declines for increasing volumetric fraction of nanoparticles.

Cooling of an electronic processor based on numerical analysis on natural convection and entropy production over a dissipating fin equipped with copper oxide/water nanofluid with Koo-Kleinstreuer-Li model

The cooling of electronic processors is a highly demanding application of natural convection due to extensive and developing usage of these devices. At this end, a numerical modelling is conducted on a real configuration of fin to find the best geometry and identify all aspects of convective flow and heat transfer around the blades. In this respect, the free convection and entropy production over a fin package are studied using numerical simulations. The fin package is filled with copper oxide/water nanofluid. The Koo-Kleinstreuer-Li (KKL) model is employed to determine the effective dynamic viscosity and effective thermal conductivity. Also, the influence of nanoparticle’s shape (four different shapes including platelet, spherical, brick and cylinder) are taken into account in calculating the properties. By means of this model, the Brownian motion will be considered in the properties. The governing equations are discretized by means of finite volume method under conditions of steady, incompressible, Newtonian and Boussinesq approximation. The investigations are proceed with studying the effect of Ra numbers (103≤Ra≤106), volumetric fraction of copper oxide–water nanofluid (0≤ϕ≤0.04) and aspect ratios of blades (AR = 30, 19.83, 14.75 and 11.7). The results approved that the pouring nanoparticle to the pure fluid is effective way to improve the thermal characteristics of operating fluid since the average Nusselt number enhances as the volume fraction increases. Moreover, it is shown that thinner fins cause more efficient thermal performance during dissipation process.

Flow and conjugate heat transfer with surface radiation characteristics of a real-scale infrared suppression device with conical funnels

The precise flow and heat transfer aspects in an infrared suppression (IRS) device are challenging because of the complicated flow features. The suction of cold ambient air and subsequent mixing with the hot exhaust gas from the turbine in cargo/naval ships happens in the IRS device. In the present research, the thermo-fluid characteristics of a two-dimensional axisymmetric IRS system consisting of conical funnels stacked one above the other are meant to study. Numerical simulations are performed for the real-scale IRS unit by solving the equations of mass, momentum, energy, and radiation in the computational domain surrounding the IRS device. In this study, the effect of conducting funnel walls with surface radiation is considered. The impact of the number of funnels on mass intake and the device outlet temperature is analyzed. The results show that the maximum air intake and minimum outlet temperature can be achieved using five funnels. The mass intake and device outlet temperature are also affected by funnel-overlapping and nozzle-overlapping. The maximum air intake and minimum outlet temperature are obtained by zero funnel-overlapping and zero nozzle-overlapping conditions. When the adiabatic funnel is replaced by conducting funnels with surface radiation, the increment in the mass intake and decrement in outlet temperature is observed. The impact of funnel wall inclination and the type of guide vanes are also discussed.