scholarly journals Origin of spray formation during impact on heated surfaces

Soft Matter ◽  
2017 ◽  
Vol 13 (41) ◽  
pp. 7514-7520 ◽  
Author(s):  
Michiel A. J. van Limbeek ◽  
Paul B. J. Hoefnagels ◽  
Chao Sun ◽  
Detlef Lohse
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Plate Thickness ◽  
Heated Plate ◽  
Spray Formation ◽  
Impact Process ◽  
The Impact

In many applications, it is crucial to control the heat transfer rate of impacting drops on a heated plate. Here we study how limited heat transfer, such as the plate thickness or low conductivity, affects the impact process.

Ferro-nanofluid squeeze film lubrication with heat transfer

2021 ◽  
pp. 135065012110276
Author(s):  
Manimegalai Kavarthalai ◽  
Vimala Ponnuswamy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Contact Time ◽  
Transfer Rate ◽  
Fluid Layer ◽  
Darcy Law ◽  
Squeeze Film ◽  
Mean Temperature ◽  
Special Cases ◽  
The Impact

A theoretical study of a squeezing ferro-nanofluid flow including thermal effects is carried out with application to bearings and articular cartilages. A representational geometry of the thin layer of a ferro-nanofluid squeezed between a flat rigid disk and a thin porous bed is considered. The flow behaviours and heat transfer in the fluid and porous regions are investigated. The mathematical problem is formulated based on the Neuringer–Rosensweig model for ferro-nanofluids in the fluid region including an external magnetic field, Darcy law for the porous region and Beavers–Joseph slip condition at the fluid–porous interface. The expressions for velocity, fluid film thickness, contact time, fluid flux, streamlines, pathlines, mean temperature and heat transfer rate in the fluid and porous regions are obtained by using a perturbation method. An asymptotic solution for the fluid layer thickness is also presented. The problem is also solved by a numerical method and the results by asymptotic analysis, perturbation and numerical methods are obtained assuming a constant force squeezing state and are compared. It is shown that the results obtained by all the methods agree well with each other. The effects of various parameters such as Darcy number, Beavers–Joseph constant and magnetization parameter on the flow behaviours, contact time, mean temperature and heat transfer rate are investigated. The novel results showing the impact of using ferro-nanofluids in the two applications under consideration are presented. The results under special cases are further compared with the existing results in the literature and are found to agree well.

Numerical and Experimental Study of the Effect of Secondary Surfaces Fixed Over a Rectangular Vortex Generator

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Uddip Kashyap ◽  
Koushik Das ◽  
Biplab Kumar Debnath
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heated Surface ◽  
Linear Regression Analysis ◽  
Vortex Generator ◽  
Base Plate ◽  
Constant Heat Flux ◽  
Heated Plate ◽  
Longitudinal Vortices

In order to cool a heated surface surrounded by fluid flow, vortex generator plays a significant role. The presence of a vortex generator in the flow creates both latitudinal and longitudinal vortices. The vortices energize the boundary layer over the heated surface and excel convective mode of heat transfer. Therefore, the strength of these vortices is directly proportional to the heat transferal rate. The present study considers a vortex generator attached to a heated base plate. The system is studied numerically and experimentally. The existing rectangular vortex generator is modified computationally with a goal to escalate the overall heat transferal rate. The role of secondary surfaces fixed over the primary surface of the rectangular vortex generator is discussed. Water flows over the surface of the base plate at a Reynolds number of 350. And the plate has a constant heat flux of 1 kW/m2. The results show that the secondary surfaces fixed parallel to the heated plate over the vortex generator significantly augment the heat transfer rate to about 13.4%. However, it enhances the drag by 5.7%. A linear regression analysis predicts the suitable placement of the secondary surface with an enhancement of heat transfer rate of about 7.6%, with a decrease in the drag by about 0.7%. In order to validate the obtained results, the best configuration is fabricated and tested experimentally. The experimental outcomes are found to complement the numerical results. In this experiment, the modification yields 25% enhancement in heat transfer rate.

Alumina nanoparticle flow within a channel with permeable walls

2020 ◽  
Vol 31 (04) ◽  
pp. 2050050 ◽  
Author(s):  
Tran Dinh Manh ◽  
Nguyen Dang Nam ◽  
Gihad Keyany Abdulrahman ◽  
R. Moradi ◽  
Houman Babazadeh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Power Law ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Expansion Ratio ◽  
Hydrodynamic Characteristics ◽  
Stream Velocity ◽  
Main Stream ◽  
The Impact

The application of the nanoparticles for the heat transfer augmentation has extensively increased in the scientific and industrial applications. In this research, semi-analytic method is used to disclose the heat transmission and flow feature of the fluid with nanoparticles among the two parallel sheets. In our model, one plate is warmed with specific heat flux while fluid is streamed from another plate which extends over times. Nanoparticles of Al2O3 are applied in the main fluid to obtain nanofluid flow. To obtained viscosity coefficient and heat conductivity of the base fluid with nanoparticles, Koo–Kleinstreuer–Li (KKL) formula is applied as reliable approach. Comprehensive investigations on different factors are done to disclose the impact of important aspects such as volume fraction of the nanoparticles, main stream velocity and expansion ratio on the main thermal and hydrodynamic characteristics of the nanofluid. It was found that the rate of the Nusselt number upsurges when the velocity of main stream, volume portion of the nanoparticles and power law index is increased. However, the increasing of the expansion ratio declines the heat transfer rate in our model. Our findings disclose that heat transfer rate is directly proportional with velocity of nanofluid as index of power law equals to zero.

3D natural convection on a horizontal and vertical thermally active plate in a closed cubical cavity

2016 ◽  
Vol 26 (8) ◽  
pp. 2528-2542 ◽  
Author(s):  
Abimanyu Purusothaman ◽  
Abderrahmane Baïri ◽  
Nagarajan Nithyadevi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Convection Heat Transfer ◽  
Numerical Code ◽  
Heated Plate ◽  
Algebraic Equations ◽  
Content Type ◽  
Cubical Cavity

Purpose The purpose of this paper is to examine numerically the natural convection heat transfer in a cubical cavity induced by a thermally active plate. Effects of the plate size and its orientation with respect to the gravity vector on the convective heat transfer and the flow structures inside the cavity are studied and highlighted. Design/methodology/approach The numerical code is based on the finite volume method with semi-implicit method for pressure-linked equation algorithm. The convective and diffusive terms in momentum equations are handled by adopting the power law scheme. Finally, the discretized sets of algebraic equations are solved by the line-by-line tri-diagonal matrix algorithm. Findings The results show that plate orientation and size plays a significant role on heat transfer. Also, the heat transfer rate is an increasing function of Rayleigh number for both orientations of the heated plate. Depending on the thermal management of the plate and its application (as in electronics), the heat transfer rate is maximized or minimized by selecting appropriate parameters. Research limitations/implications The flow is assumed to be 3D, time-dependent, laminar and incompressible with negligible viscous dissipation and radiation. The fluid properties are assumed to be constant, except for the density in the buoyancy term that follows the Boussinesq approximation. Originality/value The present work will give some additional knowledge in designing sealed cavities encountered in some engineering applications as in aeronautics, automobile, metallurgy or electronics.

A Study on Resonance Impinging and Wall Jets

2003 ◽  
Author(s):  
Toshihiko Shakouchi ◽  
Takumi Maruyama ◽  
Toshitake Ando ◽  
Koichi Tsujimoto ◽  
Atsushi Watanabe
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Impinging Jets ◽  
Heated Plate ◽  
Wall Jets ◽  
Maximum Heat ◽  
Plate Spacing ◽  
Air Jet ◽  
Nozzle Plate

Various kinds of impinging jets are used widely in many industry fields, such as the cooling of a heated plate or electronic components, drying of textiles, film, and paper because of their high heat and mass transfer rates at and near the stagnation point. Many studies on impinging jets from circular and orifice nozzles have been made [1]–[6]. It is well known that as nozzle-plate spacing decreases considerably the heat transfer rate becomes much larger, for example the maximum heat transfer rate of a circular impinging air jet with a low nozzle-plate spacing h/d = 0.1 (d: nozzle exit diameter) and Reynolds number Re = umd/ν = 2.3 × 104 is about 2.17 times of that for h/d = 0.2, but at the same time the flow resistance or operating power of the nozzle-plate system increases considerably. In order to improve or enhance the heat transfer rate, it is needed to increase the impinging mean and fluctuating velocities without increasing the operating power. To achieve this object it is considered to use a resonance jet. In this paper, the flow, acoustic and heat transfer characteristics of resonance free, impinging and wall jets are made clear experimentally. Moreover, flow visualization of the water jet flow by a tracer method is also made to examine the vortex structure at the shear layer and inside the resonance room. As a result, the heat transfer rate of the impinging jet by a resonance nozzle can be improved and enhanced considerably.

The Effect of Inclined Vertical Slats on the Free Convective Heat Transfer Rate From an Isothermal Heated Vertical Surface

2004 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
Lan Sun ◽  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Heat Generation ◽  
Transfer Rate ◽  
Heated Surface ◽  
Heated Plate ◽  
Study Results ◽  
Free Convective Heat Transfer

Free convective heat transfer from a wide heated vertical isothermal plate with adiabatic surfaces above and below the heated surface has been considered. There are a series of equally spaced vertical thin, flat surfaces (termed “slats”) near the heated surface, these surfaces being, in general, inclined to the heated surface. The slats are pivoted about their center-point and thus as their angle is changed, the distance of the tip of the slat from the plate changes. The temperature of the vertical isothermal surfaces has been assumed to be greater than the ambient temperature. Various cases have been considered to examine the effect of the geometry of the adiabatic surfaces above and below the heated plate, the effect of heat conduction in the slats and the effect of heat generation in the slats. The situation considered is an approximate model of a window with a vertical blind, the particular case where the window is hotter than the room air being considered. The heat generation that can occur in the slats is then the result of solar energy passing through the window and being absorbed by the slats. The flow has been assumed to be laminar and steady. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations have been written in dimensionless form and the resulting dimensionless equations have been solved using a commercial finite-element package. Because of the application that motivated the study, results have only been obtained for a Prandtl number of 0.7. The effect of the other dimensionless variables on the mean dimensionless heat transfer rate from the heated surface has been examined.

scholarly journals Impact of Smoluchowski Temperature and Maxwell Velocity Slip Conditions on Axisymmetric Rotated Flow of Hybrid Nanofluid past a Porous Moving Rotating Disk

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 276
Author(s):  
Umair Khan ◽  
Aurang Zaib ◽  
Iskandar Waini ◽  
Anuar Ishak ◽  
El-Sayed M. Sherif ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Radial Direction ◽  
Velocity Slip ◽  
Hybrid Nanofluid ◽  
Al2o3 Nanoparticles ◽  
Suction Parameter ◽  
The Impact

Colloidal suspensions of regular fluids and nanoparticles are known as nanofluids. They have a variety of applications in the medical field, including cell separation, drug targeting, destruction of tumor tissue, and so on. On the other hand, the dispersion of multiple nanoparticles into a regular fluid is referred to as a hybrid nanofluid. It has a variety of innovative applications such as microfluidics, heat dissipation, dynamic sealing, damping, and so on. Because of these numerous applications of nanofluids in minds, therefore, the objective of the current exploration divulged the axisymmetric radiative flow and heat transfer induced by hybrid nanofluid impinging on a porous stretchable/shrinkable rotating disc. In addition, the impact of Smoluchowski temperature and Maxwell velocity slip boundary conditions are also invoked. The hybrid nanofluid was formed by mixing the copper (Cu) and alumina (Al2O3) nanoparticles scattered in the regular (viscous) base fluid (H2O). Similarity variables are used to procure the similarity equations, and the numerical outcomes are achieved using bvp4c in MATLAB software. According to the findings, double solutions are feasible for stretching (λ>0) and shrinking cases (λ<0). The heat transfer rate is accelerated as the hybrid nanoparticles increases. The suction parameter enhances the friction factors as well as heat transfer rate. Moreover, the friction factor in the radial direction and heat transfer enrich for the first solution and moderate for the second outcome due to the augmentation δ1, while the trend of the friction factor in the radial direction is changed only in the case of stretching for both branches.

Convective–radiative heat transfer in a cavity filled with a nanofluid under the effect of a nonuniformly heated plate

2018 ◽  
Vol 28 (6) ◽  
pp. 1392-1409 ◽  
Author(s):  
Mikhail Sheremet ◽  
Sivaraj Chinnasamy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Staggered Grid ◽  
Heated Plate ◽  
Radiation Parameter ◽  
Square Cavity ◽  
Content Type ◽  
Industrial Sectors

PurposeThe purpose of this study is to examine the radiation effect on the natural convective heat transfer of an alumina–water nanofluid in a square cavity in the presence of centered nonuniformly heated plate.Design/methodology/approachThe square cavity filled with alumina–water nanofluid has a nonuniformly heated plate placed horizontally or vertically at its center. The plate is heated isothermally with linearly varying temperature. The vertical walls are cooled isothermally with a constant temperature, while the horizontal walls are insulated. The governing equations have been discretized using finite volume method on a uniformly staggered grid system. Simulations were carried out for different values of the heated plate nonuniformity parameter (λ= –1, 0 and 1), the nanoparticles solid volume fraction (Φ= 0.01 − 0.04) and the radiation parameter (Rd= 0 – 2) at the Rayleigh number ofRa= 1e+07.FindingsIt is found that the total heat transfer rate is enhanced with an increase in the radiation parameter for both the horizontal and vertical plates. The role of nanoparticles addition to the base fluid can have dual effects on the heat transfer rate by augmenting and dampening for the absence of radiation while it dampens the heat transfer rate for the presence of radiation.Originality/valueThe originality of this work is to analyze steady natural convection in a square cavity filled with a water-based nanofluid in the presence of centered nonuniformly heated plate. The results would benefit scientists and engineers to become familiar with the analysis of convective heat and mass transfer in nanofluids, and the way to predict the properties of nanofluid convective flow in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors, electronics, etc.

scholarly journals Numerical Simulation of the Thermally Developed Pulsatile Flow of a Hybrid Nanofluid in a Constricted Channel

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2410
Author(s):  
Amjad Ali ◽  
Zainab Bukhari ◽  
Gullnaz Shahzadi ◽  
Zaheer Abbas ◽  
Muhammad Umar
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Heat Transfer Rate ◽  
Pulsatile Flow ◽  
Transfer Rate ◽  
Heat Transfer Analysis ◽  
Hybrid Nanofluid ◽  
Water Based ◽  
The Impact ◽  
Constricted Channel

Heat transfer analysis of the pulsatile flow of a hybrid nanofluid through a constricted channel under the impact of a magnetic field and thermal radiation is presented. Hybrid nanofluids form a new class of nanofluids, distinguished by the thermal properties and functional utilities for improving the heat transfer rate. The behaviors of a water-based copper nanofluid and water-based copper plus a single-wall carbon nanotube, i.e., (Cu–SWCNT/water), hybrid nanofluid over each of velocity, wall shear stress, and temperature profiles, are visualized graphically. The time-dependent governing equations of the incompressible fluid flow are transformed to the vorticity-stream function formulation and solved numerically using the finite difference method. The laminar flow simulations are carried out in 2D for simplicity as the flow profiles are assumed to vary only in the 2D plane represented by the 2D Cartesian geometry. The streamlines and vorticity contours are also shown to demonstrate the flow behviour along the channel. For comparison of the flow characteristics and heat transfer rate, the impacts of variations in Hartmann number, Strouhal number, Prandtl number, and the thermal radiation parameter are analyzed. The effects of the emerging parameters on the skin friction coefficient and Nusselt number are also examined. The hybrid nanofluid is demonstrated to have better thermal characteristics than the traditional one.

An Experimental Study on Forced Convection From a Rectangular Heated Block by Acoustic Excitation in a Channel Flow

2002 ◽  
Author(s):  
J. W. Moon ◽  
S. Y. Kim ◽  
H. H. Cho
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Channel Flow ◽  
Transfer Rate ◽  
Acoustic Excitation ◽  
Pulsation Amplitude ◽  
The Impact

An experimental study on forced convection from a heated block in a pulsating channel flow has been carried out. This problem is of particular interest in various thermal applications such as electronics cooling and industrial heat exchangers. A pulsating flow is imposed by an acoustic excitation at the channel inlet and a constant heat flux is given along the surfaces of the block. The impact of the important governing parameters such as the Reynolds number, the Strouhal number, and the pulsation amplitude on the heat transfer rate from the heated block is investigated in detail. The vortex shedding frequencies generated from the block are measured and the flow around the block is visualized by means of the particle visualization technique. The experimental results show that the inlet flow pulsation and the Reynolds number substantially affect thermal transport from the heated block. The heat transfer is dramatically enhanced at the frequencies of fF=75Hz and fF=150Hz. It is found by the flow visualization that this phenomenon is related to the intensified fluid mixing at the frequencies. The increase of the pulsation amplitude also significantly amplifies the heat transfer rate from the heated block.

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