Heat-Transfer Enhancement Incorporating Fin-Like Structures Inside Droplet on Hydrophobic Surface

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Abdullah Al-Sharafi ◽  
Bekir S. Yilbas ◽  
Abdullah Al-Zahrani
Keyword(s):  
Heat Transfer ◽  
Hydrophobic Surface ◽  
Surface Characteristics ◽  
Bond Number ◽  
Temperature Fields ◽  
Experimental Conditions ◽  
Transfer Rates ◽  
Temperature Heat ◽  
The Difference ◽  
Source Flow

Enhancement of droplet heat transfer on a hydrophobic surface is examined via introducing the fin-like structures inside the droplet without altering the wetting state of the surface. A solution crystallization of polycarbonate surface is carried out and the functionalized silica particles are deposited onto the crystallized surface to create the hydrophobic surface characteristics. The ferrous particles (Fe2O3) are locally spread onto the hydrophobic surface and, later, manipulated by an external magneto-static force generating various configurations of fin-like structures inside the droplet. The droplet with fin-like structures is heated from the hydrophobic surface through introducing a constant temperature heat source. Flow and temperature fields inside the droplet are simulated in line with the experimental conditions. It is found that changing the configuration of the fin-like structures in the droplet modifies significantly the flow and temperature fields inside the droplet. The Bond number remains less than unity for all configurations of the fin-like structures while demonstrating the importance of the Marangoni current over the buoyancy current in the flow field. The presence of the fin-like structures lowers the difference between the fluid bulk and the minimum temperatures inside the droplet and improves considerably the heat transfer rates and the Nusselt number.

scholarly journals Heat transfer to a moving wire immersed in a gas fluidized bed furnace

2021 ◽  
Author(s):  
Antonio Tannas
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Steel Wire ◽  
Transfer Rates ◽  
New Correlation ◽  
Bed Temperature ◽  
Molten Lead ◽  
The Difference ◽  
Considerable Work ◽  
Work Done

In order to replace hazardous molten lead baths in the heat treatment of carbon steel wire with environmentally friendly fluidized bed furnaces a better understanding is needed of their heat transfer rates. There has been considerable work done in examining heat transfer rates to large cylinders immersed in fluidized beds, and some on wire sized ones as well, but all previous studies have been conducted on static cylinders. In order to gain a deeper understanding of heat transfer rates to a moving wire immersed in a fluidized bed furnace an apparatus has been constructed to move a wire through a fluidized bed. The heat transfer rates were calculated using the difference in inlet and outlet temperatures, wire speed and the bed temperature. As predicted, correlations for static wire were found to under-predict heat transfer rates at higher wire speeds, so a new correlation was developed by modifying an existing one.

Numerical Simulation of the Cooling Process of Cubic Shells

2011 ◽  
Author(s):  
Manabu Okura ◽  
Kiyoaki Ono
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Temperature Fields ◽  
Numerical Code ◽  
Navier Stokes ◽  
Cooling Process ◽  
Air Velocity ◽  
Navier Stokes Equations ◽  
The Difference ◽  
The Heat Transfer Coefficient

In order to keep the environment in an air-conditioned room comfortable, it is important to anticipate the air velocity and temperature fields precisely. The numerical code, solving simultaneously the Navier-Stokes equations governing flow field inside and outside the room and the heat conduction equation applying to walls, are developed. The assumption that the heat transfer coefficient between the fluid and the surface of solids is not used. This code is applied to investigate the cooling process of a cubic shell. The computational results agree with the experimental results. We also investigated the same process of the cubic shells whose walls are internally or externally insulated. The difference of the amount of heat transfer will be discussed.

Performance analysis of screw compressors – numerical simulation and experimental verification

2011 ◽  
Vol 226 (4) ◽  
pp. 968-980 ◽  
Author(s):  
S H Hsieh ◽  
Y C Shih ◽  
W-H Hsieh ◽  
F Y Lin ◽  
M J Tsai
Keyword(s):  
Heat Transfer ◽  
Screw Compressor ◽  
Pressure Curve ◽  
Discharge Process ◽  
Transfer Rates ◽  
Outlet Port ◽  
Total Process ◽  
The Difference ◽  
Verification Process ◽  
Empirical Constants

This article describes a theoretical model and computer program for calculating the pressure–volume ( PV ) diagram and the efficiency of an oil-injected screw compressor. The proposed model considers the mass and energy conservation laws, the heat transfer between air and oil, the leakages through various paths, and the discharges of air and oil. The proposed program, which uses seven empirical constants to account for the difference between the flow and the heat-transfer rates in the screw compressor and those estimated by available correlations, solves for the efficiency and the pressure curve of the compressed air. A systematic methodology for the determination of the seven empirical constants is presented in this article. Optimization is carried out to determine the seven empirical constants. With the empirical constants, which are determined with four sets of experiments, the maximum difference between the calculated and measured results in the training process, the verification process and the total process is 2.0 per cent for the volumetric and isentropic efficiencies and 5 per cent for the pressure curve. In the discharge process, the pressure in the compression chamber is noted to be affected by the area of the outlet port and the pressure in the neighbouring chambers.

Effects of the Heat Transfer at the Side Walls on Natural Convection in Cavities

1990 ◽  
Vol 112 (2) ◽  
pp. 370-378 ◽  
Author(s):  
Y. Le Peutrec ◽  
G. Lauriat
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Fluid Flows ◽  
Heat Losses ◽  
Transfer Rates ◽  
Side Walls ◽  
The Difference

Numerical solutions are obtained for fluid flows and heat transfer rates for three-dimensional natural convection in rectangular enclosures. The effects of heat losses at the conducting side walls are investigated. The problem is related to the design of cavities suitable for visualizing the flow field. The computations cover Rayleigh numbers from 103 to 107 and the thermal conductance of side walls ranging from adiabatic to commonly used glazed walls. The effect of the difference between the ambient temperature and the average temperature of the two isothermal walls is discussed for both air and water-filled enclosures. The results reported in the paper allow quantitative evaluations of the effects of heat losses to the surroundings, which are important considerations in the design of a test cell.

scholarly journals Laser interferometry - Report #HT-01-2017

2021 ◽  
Author(s):  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Light Beam ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Laser Interferometry ◽  
Local Heat ◽  
Temperature Fields ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Transfer Rates

An introduction is given to the optical setup and principle of operation of classical and holographic interferometers that are used for convective he at transfer measurements. The equations for the evaluation of the temperature field are derived and methods of analysis are discussed for both two-dimensional and three-dimensional temperature fields. Emphasis is given to techniques for measuring local heat transfer rates. For two-dimensional fields, a method is presented for measuring the surface temperature gradient directly from a finite (wedge) fringe interferogram. This “direct gradient method” is shown to be most useful for the measurement of low convective heat transfer rates. For three-dimensional fields, the equations for calculating the beam-averaged local heat flux are presented. The measurement of the fluid temperature averaged along the light beam is shown to be approximate. However, an analysis is presented showing that for most cases the error associated with temperature variations in the light beam direction is small. Digital image analysis of interferograms to obtain fringe spacings is also discussed briefly.

Forced Convection in Concentric-Sphere Heat Exchangers

1968 ◽  
Vol 90 (1) ◽  
pp. 125-129 ◽  
Author(s):  
H. A. Rundell ◽  
E. G. Ward ◽  
J. E. Cox
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Empirical Relation ◽  
Outer Sphere ◽  
Coolant Fluid ◽  
Transfer Rates ◽  
Concentric Spheres ◽  
Temperature Heat ◽  
Inner Sphere ◽  
Visualization Techniques

The first experimental investigation of forced convection of a fluid through the annulus formed by two concentric spheres was performed. The fluid enters and leaves the annulus through diametrically opposed openings in the outer sphere. The inner sphere serves as a constant-temperature heat source. Four sphere-size combinations were tested. The flow patterns in the annulus were established by flow visualization techniques; characteristic photographic results are presented. Energy considerations include heat transfer rates, inner-sphere surface temperatures, and temperature traverses of the coolant fluid. An empirical relation correlates the heat transfer data.

Heat Transfer and Friction Characteristics Analyses between WPC Materials and Conveyor Plate

2012 ◽  
Vol 501 ◽  
pp. 467-472
Author(s):  
Yue Tang ◽  
Wen Min Tu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heating Temperature ◽  
Difficulty Level ◽  
Wood Powder ◽  
Heat Transfer Characteristics ◽  
Friction Characteristics ◽  
Temperature Heat ◽  
The Difference

Through experiments to measure the warming time of top and bottom surfaces of the conveyor plate at different heating temperature, the difference in temperature of top and bottom surfaces was used to analyse the heat transfer characteristics of conveyor plate. And the static difference in temperature heat transfer rate was used to reflect difficulty level of the conveyor plate top and bottom surfaces temperatures close to each other. The solid transportation effect of the wood powder and PVC mixture was confirmed to be best, and the best drying and transferring temperature should be around 80 °C.

Heat Transfer between Parallel Walls: An Interferometric Investigation

1972 ◽  
Vol 14 (2) ◽  
pp. 107-127 ◽  
Author(s):  
R. G. Brooks ◽  
S. D. Probert
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Temperature Fields ◽  
Heated Wall ◽  
Thermal Boundary Conditions ◽  
Numerical Studies ◽  
Air Layers ◽  
Interferometric Investigation ◽  
The Difference

The temperature fields and the transfer of heat within vertical, inclined and horizontal air layers are examined for each of three different heat transfer regimes. Experimental evidence is offered which explains the difference between the heat transfer correlations of previous investigations in which the Nusselt modulus is based on the heat flux leaving the heated wall and those in which the Nusselt number is based upon the rate at which heat is transferred to the cooled wall. It is also shown that some of the thermal boundary conditions which have generally been assumed in numerical studies are unrealistic.

scholarly journals Laser interferometry - Report #HT-01-2017

2021 ◽  
Author(s):  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Light Beam ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Laser Interferometry ◽  
Local Heat ◽  
Temperature Fields ◽  
Fluid Temperature ◽  
Two Dimensional ◽  
Transfer Rates

An introduction is given to the optical setup and principle of operation of classical and holographic interferometers that are used for convective he at transfer measurements. The equations for the evaluation of the temperature field are derived and methods of analysis are discussed for both two-dimensional and three-dimensional temperature fields. Emphasis is given to techniques for measuring local heat transfer rates. For two-dimensional fields, a method is presented for measuring the surface temperature gradient directly from a finite (wedge) fringe interferogram. This “direct gradient method” is shown to be most useful for the measurement of low convective heat transfer rates. For three-dimensional fields, the equations for calculating the beam-averaged local heat flux are presented. The measurement of the fluid temperature averaged along the light beam is shown to be approximate. However, an analysis is presented showing that for most cases the error associated with temperature variations in the light beam direction is small. Digital image analysis of interferograms to obtain fringe spacings is also discussed briefly.

Natural Convection Heat Transfer Through Inclined Longitudinal Slots

1984 ◽  
Vol 106 (4) ◽  
pp. 824-829 ◽  
Author(s):  
J. G. Symons ◽  
M. K. Peck
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Aspect Ratio ◽  
Convective Flow ◽  
Convection Heat Transfer ◽  
Flow Measurements ◽  
Transfer Rates ◽  
Isothermal Surface ◽  
Aspect Ratios ◽  
The Difference

The convective rates of heat transfer through inclined longitudinal slots is studied for the case where heat is transferred from a lower heated isothermal surface, through the slots, to an upper cooled isothermal surface. Experimental data are given for longitudinal slots having aspect ratios from 6–12, slot heights of 25–60 mm, inclinations from horizontal to vertical, and Ra < 107. Data are also given for a transverse slot of aspect ratio 6, for inclinations from horizontal to vertical, and Ra < 107. It is shown that convective heat transfer rates are essentially independent of slot orientation for inclinations up to 15 deg from the horizontal, but longitudinal slots are more effective in suppressing natural convection than transverse slots with the same aspect ratio, for inclinations from 24 to 75 deg from the horizontal. The difference in heat transfer rates for longitudinal and transverse slots inclined between 24 and 75 deg from the horizontal are shown to be due to different convective flows occurring in each slot. The heat flow measurements are supported by convective flow visualization experiments which demonstrate the modes of convective flow within slots.

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