scholarly journals Convective heat transfer in a dusty ferromagnetic fluid over a stretching surface with prescribed surface temperature/heat flux including heat source/sink

2018 ◽  
Vol 46 (3) ◽  
pp. 399 ◽  
Author(s):  
A Majeed ◽  
A Zeeshan ◽  
RSR Gorla
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Source ◽  
Surface Temperature ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Stretching Surface ◽  
Temperature Heat ◽  
Ferromagnetic Fluid ◽  
Source Sink

Role of blood as heat source or sink in human limbs during local cooling and heating

1994 ◽  
Vol 76 (5) ◽  
pp. 2084-2094 ◽  
Author(s):  
M. B. Ducharme ◽  
P. Tikuisis
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Steady State ◽  
Heat Source ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Total Heat Loss ◽  
Partial Immersion ◽  
Thermal Steady State

The objective of the present study was to investigate the relative contribution of the convective heat transfer in the forearm and hand to 1) the total heat loss during partial immersion in cold water [water temperature (Tw) = 20 degrees C] and 2) the heat gained during partial immersion in warm water (Tw = 38 degrees C). The heat fluxes from the skin of the forearm and finger were continuously monitored during the 3.5-h immersion of the upper limb (forearm and hand) with 23 recalibrated heat flux transducers. The last 30 min of the partial immersion were conducted with an arterial occlusion of the forearm. The heat flux values decreased during the occlusion period at Tw = 20 degrees C and increased at Tw = 38 degrees C for all sites, plateauing only for the finger to the value of the tissue metabolic rate (124.8 +/- 29.0 W/m3 at Tw = 20 degrees C and 287.7 +/- 41.8 W/m3 at Tw = 38 degrees C). The present study shows that, at thermal steady state during partial immersion in water at 20 degrees C, the convective heat transfer between the blood and the forearm tissue is the major heat source of the tissue and accounts for 85% of the total heat loss to the environment. For the finger, however, the heat produced by the tissue metabolism and that liberated by the convective heat transfer are equivalent. At thermal steady state during partial immersion in water at 38 degrees C, the blood has the role of a heat sink, carrying away from the limb the heat gained from the environment and, to a lesser extent (25%), the metabolic and conductive heats. These results suggest that during local cold stress the convective heat transfer by the blood has a greater role than that suggested by previous studies for the forearm but a lesser role for the hand.

scholarly journals Improvement of the Heat-Dissipating Performance of Powder Coating with Graphene

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1321
Author(s):  
Fei Kung ◽  
Ming-Chien Yang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Temperature ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Dissipation ◽  
Powder Coating ◽  
Aluminum Plate ◽  
Graphene Nanoparticles

In this study, the epoxy powder was blended with graphene to improve its thermal conductivity and heat dissipation efficiency. The thermal conductivity of the graphene-loaded coating was increased by 167 folds. In addition, the emissivity of the graphene-loaded coating was 0.88. The epoxy powder was further coated on aluminum plate through powder coating process in order to study the effect on the performance of heat dissipation. In the case of natural convective heat transfer, the surface temperature of the graphene-loaded coated aluminum plate was 96.7 °C, which was 27.4 °C lower than that of bare aluminum plate (124.1 °C) at a heat flux of 16 W. In the case of forced convective heat transfer, the surface temperature decreased from 77.8 and 68.3 °C for a heat flux of 16 W. The decrease in temperature can be attributed to the thermal radiation. These results show that the addition of graphene nanoparticles in the coating can increase the emissivity of the aluminum plate and thus improving the heat dissipation.

Analysis of flow and heat transfer over stretching/shrinking and porous surfaces

2021 ◽  
pp. 875608792110258
Author(s):  
Azhar Ali ◽  
Dil Nawaz Khan Marwat ◽  
Aamir Ali
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Current Model ◽  
Uniform Heat Flux ◽  
Similarity Transformations ◽  
Flow And Heat Transfer ◽  
Special Cases ◽  
Porous Surfaces

Flows and heat transfer over stretching/shrinking and porous surfaces are studied in this paper. Unusual and generalized similarity transformations are used for simplifying governing equations. Current model includes all previous cases of stretched/shrunk flows with thermal effects discussed so far. Moreover, we present three different cases of thermal behavior (i) prescribed surface temperature (ii) Variable/uniform convective heat transfer at plat surface and (iii) prescribed variable/uniform heat flux. Stretching/shrinking velocity Uw(x), porosity [Formula: see text], heat transfer [Formula: see text], heat flux [Formula: see text] and convective heat transfer at surface are axial coordinate dependent. Boundary layer equations and boundary conditions are transformed into nonlinear ODEs by introducing unusual and generalized similarity transformations for the variables. These simplified equations are solved numerically. Final ODEs represent suction/injection, stretching/shrinking, temperature, heat flux, convection effects and specific heat. This current problem encompasses all previous models as special cases which come under the scope of above statement (title). The results of classical models are scoped out as a special case by assigning proper values to the parameters. Numerical result shows that the dual solutions can be found for different possible values of the shrinking parameter. A stability analysis is accomplished and apprehended in order to establish a criterion for determining linearly stable and physically compatible solutions. The significant features and diversity of the modeled equations are scrutinized by recovering the previous problems of fluid flow and heat transfer from a uniformly heated sheet of variable (uniform) thickness with variable (uniform) stretching/shrinking and injection/suction velocities.

Scalable Heat Transfer Characterization on Film Cooled Geometries Based on Discrete Green’s Functions

2020 ◽  
Author(s):  
Jorge Saavedra ◽  
Venkat Athmanathan ◽  
Guillermo Paniagua ◽  
Terrence Meyer ◽  
Doug Straub ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flat Plate ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Green's Functions ◽  
Green’S Functions ◽  
Numerical Procedure ◽  
Local Heat Transfer ◽  
Sensitivity Matrix

Abstract The aerothermal characterization of film cooled geometries is traditionally performed at reduced temperature conditions, which then requires a debatable procedure to scale the convective heat transfer performance to engine conditions. This paper describes an alternative engine-scalable approach, based on Discrete Green’s Functions (DGF) to evaluate the convective heat flux along film cooled geometries. The DGF method relies on the determination of a sensitivity matrix that accounts for the convective heat transfer propagation across the different elements in the domain. To characterize a given test article, the surface is discretized in multiple elements that are independently exposed to perturbations in heat flux to retrieve the sensitivity of adjacent elements, exploiting the linearized superposition. The local heat transfer augmentation on each segment of the domain is normalized by the exposed thermal conditions and the given heat input. The resulting DGF matrix becomes independent from the thermal boundary conditions, and the heat flux measurements can be scaled to any conditions given that Reynolds number, Mach number, and temperature ratios are maintained. The procedure is applied to two different geometries, a cantilever flat plate and a film cooled flat plate with a 30 degree 0.125” cylindrical injection orifice with length-to-diameter ratio of 6. First, a numerical procedure is applied based on conjugate 3D Unsteady Reynolds Averaged Navier Stokes simulations to assess the applicability and accuracy of this approach. Finally, experiments performed on a flat plate geometry are described to validate the method and its applicability. Wall-mounted thermocouples are used to monitor the surface temperature evolution, while a 10 kHz burst-mode laser is used to generate heat flux addition on each of the discretized elements of the DGF sensitivity matrix.

Convective Heat Transfer Performance of FC-72 in a Pin-Finned Channel

2008 ◽  
Author(s):  
Liang-Han Chien ◽  
S.-Y. Pei ◽  
T.-Y. Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Rate ◽  
Smooth Surface ◽  
Heat Transfer Performance ◽  
Fluid Temperature ◽  
Transfer Performance ◽  
Finned Surface

This study investigates the influence of the heat flux and mass velocity on convective heat transfer performance of FC-72 in a rectangular channel of 20mm in width and 2 mm in height. The heated side has either a smooth surface or a pin-finned surface. The inlet fluid temperature is maintained at 30°C. The total length of the test channel is 113 mm, with a heated length of 25mm. The flow rate varies between 80 and 960 ml/min, and the heat flux sets between 18 and 50 W/cm2. The experimental results show that the controlling variable is heat flux instead of flow rate because of the boiling activities in FC-72. At a fixed flow rate, the pin-finned surface yields up to 20% higher heat transfer coefficient and greater critical heat flux than those of a smooth surface.

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