Heat-Transfer and Flow-Friction Characteristics of Nine Pin-Fin Surfaces

1966 ◽  
Vol 88 (4) ◽  
pp. 383-390 ◽  
Author(s):  
G. Theoclitus
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Experimental Results ◽  
Friction Characteristics ◽  
Flow Friction ◽  
Pin Fin

Experimental results for convective heat-transfer and flow-friction characteristics are presented for pin-fin surfaces with in-line square pin spacing of 2D0, 3D0 and 4D0 and with plate spacings of 4D0, 8D0, 12D0.

Heat-Transfer and Flow-Friction Characteristics of Skewed-Passage and Glass-Ceramic Heat-Transfer Surfaces

1965 ◽  
Vol 87 (1) ◽  
pp. 72-86 ◽  
Author(s):  
C. P. Howard
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Convective Heat Transfer ◽  
Gas Turbine ◽  
Convective Heat ◽  
Glass Ceramic ◽  
Compact Heat Exchanger ◽  
Friction Characteristics ◽  
Transfer Data ◽  
Flow Friction

Experimental results for convective heat-transfer and flow-friction characteristics of three skewed-passage and four glass-ceramic compact heat-exchanger surfaces are presented which should be of practical use, particularly in the design of gas-turbine regenerators. The heat-transfer data were obtained by the transient technique.

Convective Heat Transfer Characteristics of Silver-Water Nanofluid Under Laminar and Turbulent Flow Conditions

2012 ◽  
Vol 4 (3) ◽  
Author(s):  
Lazarus Godson ◽  
B. Raja ◽  
D. Mohan Lal ◽  
S. Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Pure Water ◽  
Convective Heat Transfer Coefficient ◽  
Experimental Results

The convective heat transfer coefficient and pressure drop of silver-water nanofluids is measured in a counter flow heat exchanger from laminar to turbulent flow regime. The experimental results show that the convective heat transfer coefficient of the nanofluids increases by up to 69% at a concentration of 0.9 vol. % compared with that of pure water. Furthermore, the experimental results show that the convective heat transfer coefficient enhancement exceeds the thermal conductivity enhancement. It is observed that the measured heat transfer coefficient is higher than that of the predicted ones using Gnielinski equation by at least 40%. The use of the silver nanofluid has a little penalty in pressure drop up to 55% increase 0.9% volume concentration of silver nanoparticles.

A Numerical Study of the Flow and Heat Transfer in the Pin Fin-Dimple Channels With Various Dimple Depths

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Yu Rao ◽  
Yamin Xu ◽  
Chaoyi Wan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Number Range ◽  
Flow Friction ◽  
Pin Fin ◽  
Flow And Heat Transfer

A numerical study was conducted to investigate the effects of dimple depth on the flow and heat transfer characteristics in a pin fin-dimple channel, where dimples are located spanwisely between the pin fins. The study aimed at promoting the understanding of the underlying convective heat transfer mechanisms in the pin fin-dimple channels and improving the cooling design for the gas turbine components. The flow structure, friction factor, and heat transfer performance of the pin fin-dimple channels with various dimple depths have been obtained and compared with each other for the Reynolds number range of 8200–80,800. The study showed that, compared to the pin fin channel, the pin fin-dimple channels have further improved convective heat transfer performance, and the pin fin-dimple channel with deeper dimples shows relatively higher Nusselt number values. The study still showed a dimple depth-dependent flow friction performance for the pin fin-dimple channels compared to the pin fin channel, and the pin fin-dimple channel with shallower dimples shows relatively lower friction factors over the studied Reynolds number range. Furthermore, the computations showed the detailed characteristics in the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the heat transfer enhancement and flow friction reduction phenomenon in the pin fin-dimple channels.

Unsteady Heat Transfer Around Low Aspect Ratio Cylinders in an Array

2016 ◽  
Author(s):  
Shawn Siroka ◽  
Melissa Shallcross ◽  
Stephen Lynch
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Flux ◽  
Pin Fin ◽  
Low Aspect Ratio ◽  
Minimum Heat

Cylindrical pins, often called pin fins, are used to create turbulence and promote convective heat transfer within many devices, ranging from computer heat sinks to the trailing edge of jet engine turbine blades. Previous experiments have measured the time-averaged heat transfer over a single pin as well as the flow fields around the pin. However, in this study, focus is placed on the instantaneous heat flux around the centerline of a low aspect-ratio pin within an array. Time-mean and unsteady convective heat flux are measured around the circumference of an isothermal heated test pin via a microsensor located at the surface. The pin is positioned at various locations within a staggered array in a large-scale wind tunnel. Reynolds numbers from 3,000 to 50,000, based on pin diameter and maximum velocity between pins, are tested with a streamwise spacing of 1.73 diameters between rows, a spanwise spacing of 2 diameters, and a pin height of 1 diameter. The time-averaged and standard deviation of convective heat flux around the pin is higher over most of the pin surface for pins in downstream row positions of an array relative to the first row pin, except in the wake which has similar levels for all rows. For a given pin position in the array, as the Reynolds number increases, the point of minimum heat transfer moves circumferentially upstream on the pin fin, corresponding to earlier transition of the pin boundary layer. Also, for a given Reynolds number, the minimum heat transfer point on the pin circumference moves upstream for pins further into the array, due to the high turbulence levels within the array which cause early transition. For a single pin row with no downstream pins, heat transfer fluctuations are very high on the backside of the pin due to the significant unsteadiness in the pin wake, but heat transfer fluctuations are suppressed for a pin with downstream rows due to the confining effects of the close spacing. The results from this study can be used to design pin-fin arrays that take advantage of unsteadiness and increase overall convective heat transfer for various industry components.

Convective Heat Transfer Enhancement With Micro Pin-Fin Surfaces Cooled by a Piezoelectrically-Driven Translational Agitator

2012 ◽  
Author(s):  
Taiho Yeom ◽  
Terrence W. Simon ◽  
Tao Zhang ◽  
Mark T. North ◽  
Tianhong Cui
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Channel Flow ◽  
Convective Heat ◽  
High Frequency ◽  
Single Channel ◽  
Heated Surface ◽  
Large Displacement ◽  
Air Cooling ◽  
Pin Fin

Air cooling of electronic equipment continues to hold many advantages over liquid cooling in terms of simplicity, reliability, cost, etc. Many active and passive air cooling techniques have been developed to meet the thermal challenges of modern, high-power electronics. Active cooling includes such features as piezoelectric flapping fans and synthetic jets that could directly break down and thin the thermal boundary layers on heated surfaces. A microchannel bank of fins, micro pin-fin surfaces, etc. are passive methods for increasing heat transfer area. In the current study, both active and passive methods, piezoelectric translational agitators and micro pin fin arrays, are employed to dramatically enhance convective heat transfer rates. A piezoelectric stack actuator coupled with an oval loop shell displacement amplifier was utilized to generate high-frequency and large-displacement translational agitation over the micro pin fin surface. Two different micro pin-fin surfaces were fabricated using copper and the LIGA process. Heat transfer experiments were performed in a single channel that houses a one-sided, heated surface with attached micro pin fins. The piezoelectric translational agitator oscillates at a high frequency of 596 Hz with a large displacement of up to 1.8 mm. The heat transfer coefficients on the micro pin-fin surface cooled by the agitator and various channel through-flows were compared with those of plain surfaces under the same channel flow rates. A maximum improvement of 222% in the heat transfer rate was achieved when the agitator was operated, the micro pin-fin surface was in place and the channel flow velocity was 11.6 m/sec, compared to that of a non-agitated plain surface case with the same flow rate.

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