scholarly journals Heat exchange between a bouncing drop and a superhydrophobic substrate

2017 ◽  
Vol 114 (27) ◽  
pp. 6930-6935 ◽  
Author(s):  
Samira Shiri ◽  
James C. Bird
Keyword(s):  
Heat Transfer ◽  
Water Drop ◽  
Heat Transfer Process ◽  
Physical Parameters ◽  
Short Contact Time ◽  
Bulk Substrate ◽  
Trapped Gas ◽  
Capillary Dynamics ◽  
Air Pockets

The ability to enhance or limit heat transfer between a surface and impacting drops is important in applications ranging from industrial spray cooling to the thermal regulation of animals in cold rain. When these surfaces are micro/nanotextured and hydrophobic, or superhydrophobic, an impacting drop can spread and recoil over trapped air pockets so quickly that it can completely bounce off the surface. It is expected that this short contact time limits heat transfer; however, the amount of heat exchanged and precise role of various parameters, such as the drop size, are unknown. Here, we demonstrate that the amount of heat exchanged between a millimeter-sized water drop and a superhydrophobic surface will be orders of magnitude less when the drop bounces than when it sticks. Through a combination of experiments and theory, we show that the heat transfer process on superhydrophobic surfaces is independent of the trapped gas. Instead, we find that, for a given spreading factor, the small fraction of heat transferred is controlled by two dimensionless groupings of physical parameters: one that relates the thermal properties of the drop and bulk substrate and the other that characterizes the relative thermal, inertial, and capillary dynamics of the drop.

scholarly journals A Computational Study on the Role of Parameters for Identification of Thyroid Nodules by Infrared Images (and Comparison with Real Data)

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4459
Author(s):  
José R. González ◽  
Charbel Damião ◽  
Maira Moran ◽  
Cristina A. Pantaleão ◽  
Rubens A. Cruz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thyroid Nodules ◽  
Numerical Study ◽  
Computational Study ◽  
Internal Heat ◽  
Heat Transfer Process ◽  
The Body ◽  
Physical Parameters ◽  
Infrared Sensors ◽  
Wide Range

According to experts and medical literature, healthy thyroids and thyroids containing benign nodules tend to be less inflamed and less active than those with malignant nodules. It seems to be a consensus that malignant nodules have more blood veins and more blood circulation. This may be related to the maintenance of the nodule’s heat at a higher level compared with neighboring tissues. If the internal heat modifies the skin radiation, then it could be detected by infrared sensors. The goal of this work is the investigation of the factors that allow this detection, and the possible relation with any pattern referent to nodule malignancy. We aim to consider a wide range of factors, so a great number of numerical simulations of the heat transfer in the region under analysis, based on the Finite Element method, are performed to study the influence of each nodule and patient characteristics on the infrared sensor acquisition. To do so, the protocol for infrared thyroid examination used in our university’s hospital is simulated in the numerical study. This protocol presents two phases. In the first one, the body under observation is in steady state. In the second one, it is submitted to thermal stress (transient state). Both are simulated in order to verify if it is possible (by infrared sensors) to identify different behavior referent to malignant nodules. Moreover, when the simulation indicates possible important aspects, patients with and without similar characteristics are examined to confirm such influences. The results show that the tissues between skin and thyroid, as well as the nodule size, have an influence on superficial temperatures. Other thermal parameters of thyroid nodules show little influence on surface infrared emissions, for instance, those related to the vascularization of the nodule. All details of the physical parameters used in the simulations, characteristics of the real nodules and thermal examinations are publicly available, allowing these simulations to be compared with other types of heat transfer solutions and infrared examination protocols. Among the main contributions of this work, we highlight the simulation of the possible range of parameters, and definition of the simulation approach for mapping the used infrared protocol, promoting the investigation of a possible relation between the heat transfer process and the data obtained by infrared acquisitions.

scholarly journals The role of the saver in a HPLCs heat transfer process: a transient analysis

2017 ◽  
Vol 796 ◽  
pp. 012033 ◽  
Author(s):  
M. Lorenzini ◽  
P. Valdiserri ◽  
M. Pagnoni
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Transient Analysis ◽  
Heat Transfer Process

Non-uniform nanoparticle concentration effects on moving plate boundary layer

2016 ◽  
Vol 94 (11) ◽  
pp. 1222-1227 ◽  
Author(s):  
A. Mehmood ◽  
M. Usman
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Plate Boundary ◽  
Convective Transport ◽  
Physical Parameters ◽  
Nanoparticle Concentration ◽  
Concentration Effects ◽  
Moving Plate ◽  
Layer Flow

The inclusion of small nano-sized particles in a pure fluid changes the material properties of the resulting mixture, called a nanofluid, significantly. To understand the role of material particles on the convection process one needs an efficient modeling of the nanofluid. The homogeneous modeling is observed to underpredict the rate of heat transfer. This fact motivates the utilization of non-homogeneous modeling. In this study we considered the classical Sakiadis moving plate boundary layer flow of a nanofluid. Non-homogeneous concentration, which is a consequence of convective transport of nanoparticles within the boundary layer, has been utilized to calculate the heat transfer enhancement. Effects of different physical parameters have been investigated on the expedition of heat transfer phenomena. It is noted that significant increase in the rate of heat transfer is observed when the nanoparticle concentration is non-uniform across the boundary layer.

scholarly journals THE ROLE OF CONCAVE WALLS OF INNER CYLINDER ON NATURAL CONVECTION IN ANNULAR SPACE

2020 ◽  
Vol 3 (2) ◽  
pp. 24-28
Author(s):  
Houssem Laidoudi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Transfer Rate ◽  
Physical Parameters ◽  
Geometrical Parameters ◽  
Annular Space ◽  
Square Cylinder ◽  
Square Cylinders

The objective of the present research is to provide correct results of the roles of physical and geometrical parameters on the natural convection in an annular space of square cylinders. The physical parameters of the fluid are considered as follow: Prandtl number (0.71, 7.01, 50 and 100) and Rayleigh number (10 power 3, and 10 power 4). However, the studied geometrical modification is based on converting the walls of inner square cylinder from the straight form to the concave form. The work is well done numerically. The predicted results are mainly shown as representative contours of streamlines and isotherms. It was understood that the concave walls of inner cylinder reduces the heat transfer rate that can be useful to use this form in insulating applications instead of straight walls.

scholarly journals Darcy Brinkman Equations for Hybrid Dusty Nanofluid Flow with Heat Transfer and Mass Transpiration

Computation ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 118
Author(s):  
K. N. Sneha ◽  
U. S. Mahabaleshwar ◽  
Rachid Bennacer ◽  
Mohammed EL. Ganaoui
Keyword(s):  
Heat Transfer ◽  
Chemical Engineering ◽  
Exact Analytical Solution ◽  
Polymer Processing ◽  
Heat Transfer Process ◽  
Current Work ◽  
Physical Parameters ◽  
Processing Unit ◽  
Brinkman Equations ◽  
Non Linear

In the current work, we have investigated the flow past a semi-infinite porous solid media, after presenting a similarity transformation, governing equations mapped to a system of non-linear PDE. The flow of a dusty fluid and heat transfer through a porous medium have few applications, viz., the polymer processing unit of a geophysical, allied area, and chemical engineering plant. Further, we had the option to get an exact analytical solution for the velocity to the equation that is non-linear. The highlight of the current work is the flow of hybrid dusty nanofluid due to Darcy porous media through linear thermal radiation with the assistance of an analytical process. The hybrid dusty nanofluid has significant features improving the heat transfer process and is extensively developed in manufacturing industrial uses. It was found that the basic similarity equations admit two phases for both stretching/shrinking surfaces. The existence of computation on velocity and temperature profile is presented graphically for different estimations of various physical parameters.

The role of horizontal rolls in rapid intensification of cyclonic vortex

2021 ◽  
Author(s):  
Andrei Sukhanovskii ◽  
Elena Popova
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Process ◽  
Rapid Intensification ◽  
Rapid Variation ◽  
Convective Structures ◽  
Cyclonic Vortex ◽  
Laboratory Analog ◽  
Boundary Layer Formation

<p>The present laboratory study is focused on the role of convective rolls in enhancement of the heat flux from the sea and triggering of the process of rapid intensification of tropical cyclones. The appearance of coherent convective structures such as thermals and rolls are registered by different optical techniques and temperature measurements. Two-dimensional velocity fields are used for the study of the structure and characteristics of the flow. The heat flux from the heating plate to the fluid is measured directly. Obtained results clearly show that rapid intensification of a laboratory analog of a tropical cyclone is tightly linked with the heat transfer process in the boundary layer. Formation of secondary convective structures strongly increases the heat transfer and intensity of convective circulation. Intensity of radial inflow is a crucial aspect for the intensification of cyclonic vortex, hence rapid variation of the heat transfer is a factor that has a substantial influence on the dynamics of a laboratory vortex. </p>

Heat Transfer From a Moving and Evaporating Meniscus on a Heated Surface

2003 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Wai Keat Kuan
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Heated Surface ◽  
Water Flow Rate ◽  
Transient Heat Conduction ◽  
Heat Transfer Process ◽  
Conduction Model ◽  
Experimental Heat ◽  
Experimental Heat Transfer

A stable meniscus is formed between a needle dispensing water over a heated circular face of a rotating copper block. The needle is offset from the axis of rotation and thus forms a moving meniscus. The water flow rate, heater surface temperature and the speed of rotation are controlled to provide a stable meniscus with complete evaporation of water without any meniscus break-up. The experimental heat transfer rate is compared with the transient heat conduction model developed here. The results indicate that the transient heat conduction plays a major role in the heat transfer process from a moving meniscus. The study provides an important insight on the role of transient conduction around a nucleating bubble in pool boiling.

Expanding/contracting fin of rectangular profile

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Turkyilmazoglu M.
Keyword(s):  
Heat Transfer ◽  
Transfer Process ◽  
Transfer Problem ◽  
Rectangular Cross Section ◽  
Heat Transfer Process ◽  
Heat Transfer Analysis ◽  
Physical Parameters ◽  
Specific Rate ◽  
Content Type ◽  
Fin Efficiency

Purpose The purpose of this paper is to study an expandable or contractible metallic fin and heat transfer process. The fin is assumed to be thin having a rectangular cross section. It is attached to a hot surface with a time-dependent temperature, and its tip extends to a medium (fluid) of an ambient temperature. With the insulated wall constraint at the tip, the tip of the metallic fin has the property of expanding or contracting in time at a specific rate. Design/methodology/approach The corresponding physical problem is so formulated that the unsteady heat transfer problem is governed by means of a similarity variable represented by a second-order ordinary differential equation. The system can be reduced to the traditional well-documented steady state fin problem often studied in the literature, if the unsteadiness is turned off from the formulated system. Findings The system is then solved analytically for the temperature distribution through the fin. The fin tip temperatures are calculated, and the heat transfer analysis is made with varying physical parameters. And finally, observations are discussed leading to better fin efficiency and heat transfer enhancement. Originality/value An expandable or contractible metallic fin and heat transfer process are analyzed for the first time in the literature. Full solutions are presented, whose numerical correspondence is discussed through graphical and tabular forms.

scholarly journals Heat transfer enhancement in rotating disk boundary layer

2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2467-2482
Author(s):  
Ahmer Mehmood ◽  
Muhammad Usman
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Enhancement ◽  
Rotating Disk ◽  
Heat Transfer Process ◽  
Working Fluid ◽  
Bench Mark ◽  
Physical Parameters ◽  
Transfer Enhancement ◽  
Severe Condition

A generally admitted fact about the nanofluids is the expedition of heat transfer process in comparison to pure fluids. The calculation of enhanced rate of heat transfer depends strongly upon the nanofluid modeling. Following the experimental evidence most of the researchers assume the nanofluid to be a homogeneous mixture. However, this is a severe condition that results in under-prediction of heat transfer rates. Due to the ongoing convection phenomena the nanoparticle concentration is actually non-homogeneous within the boundary-layer because of the presence of concentration gradients. The objective of this study is to calculate the heat transfer enhancement in 3-D boundary-layer when the working fluid is a nanofluid. The rotating disk geometry, which perhaps serves as the bench mark for the 3-D boundary-layers, have been chosen for the purpose here. The non-homogeneous nanofluid modeling has been utilized and a percent increase in Nusselt number has been calculated. Detailed analyses of flow and heat transfer phenomena for nanofluids have been conducted under the influence of several physical parameters.

scholarly journals Entropy Rates and Efficiency of Convecting-Radiating Fins

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1643
Author(s):  
Claudio Giorgi ◽  
Federico Zullo
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Transfer Process ◽  
Heat Transfer Process ◽  
Numerical Results ◽  
Entropy Rate ◽  
Fluid Temperature ◽  
Standard Definition ◽  
Definition Of

We present a novel indicator for the effectiveness of longitudinal, convecting-radiating fins to dissipate heat. Starting from an analysis of the properties of the entropy rate of the steady state, we show how it is possible to assess the efficiency of such devices by looking at the amount of entropy produced in the heat transfer process. Our study concerns both purely convective fins and convection-radiant fins and takes advantage of explicit expressions for the distribution of heat along the fin. It is shown that, in a suitable limit, the standard definition of efficiency and the entropic definition coincide. The role of the fluid temperature is explicit in the new definition and in the purely convective case. An application to an aluminium fin is given. Analytical and numerical results are discussed.

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