scholarly journals Heat Transfer From a Finned Surface in Ducted Air Jet Suction and Impingement

1999 ◽  
Vol 122 (3) ◽  
pp. 282-285 ◽  
Author(s):  
Luis A. Brignoni ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Jet Impingement ◽  
Target Distance ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Air Jet ◽  
Finned Surface ◽  
Different Diameters

Experimental measurements were obtained to characterize the thermal performance of ducted air suction in conjunction with a pin-fin heat sink. Four single nozzles of different diameters and two multiple-nozzle arrays were studied at a fixed nozzle-to-target distance, for different turbulent Reynolds numbers 5000⩽Re⩽20,000. Variations of nozzle-to-target distance, i.e., open area, in ducted suction were found to have a strong effect on heat transfer especially with the larger diameter single nozzle and both multiple-nozzle arrays. Enhancement factors were computed with the heat sink in suction flow, relative to a bare surface, and were in the range of 8.3 to 17.7, with the largest value being obtained for the nine-nozzle array. Results from the present study on air jet suction are compared with previous experiments with air jet impingement on the pin-fin heat sink. Average heat transfer coefficients and thermal resistance values are reported for the heat sink as a function of Reynolds number, air flow rate, and pumping power. [S1043-7398(00)00903-8]

Single-Phase and Boiling Cooling of Small Pin Fin Arrays by Multiple Nozzle Jet Impingement

1996 ◽  
Vol 118 (1) ◽  
pp. 21-26 ◽  
Author(s):  
David Copeland
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Single Phase ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Pin Fin Arrays

Experimental measurements of multiple nozzle submerged jet array impingement single-phase and boiling heat transfer were made using FC-72 and 1 cm square copper pin fin arrays, having equal width and spacing of 0.1 and 0.2 mm, with aspect ratios from 1 to 5. Arrays of 25 and 100 nozzles were used, with diameters of 0.25 to 1.0 mm providing nozzle area from 5 to 20 mm2 (5 to 20% of the heat source base area). Flow rates of 2.5 to 10 cm3/s (0.15 to 0.6 l/min) were studied, with nozzle velocities from 0.125 to 2 m/s. Single nozzles and smooth surfaces were also evaluated for comparison. Single-phase heat transfer coefficients (based on planform area) from 2.4 to 49.3 kW/m2 K were measured, while critical heat flux varied from 45 to 395 W/cm2. Correlations of the single-phase heat transfer coefficient and critical heat flux as functions of pin fin dimensions, number of nozzles, nozzle area and liquid flow rate are provided.

Cryogenic Single-Phase Heat Transfer in a Microscale Pin Fin Heat Sink

2013 ◽  
Author(s):  
Eric D. Truong ◽  
Erfan Rasouli ◽  
Vinod Narayanan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Single Phase ◽  
Flow Direction ◽  
Heat Sinks ◽  
Variable Cross ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients

A combined experimental and computational fluid dynamics study of single-phase liquid nitrogen flow through a microscale pin-fin heat sink is presented. Such cryogenic heat sinks find use in applications such as high performance computing and spacecraft thermal management. A circular pin fin heat sink in diameter 5 cm and 250 micrometers in depth was studied herein. Unique features of the heat sink included its variable cross sectional area in the flow direction, variable pin diameters, as well as a circumferential distribution of fluid into the pin fin region. The stainless steel heat sink was fabricated using chemical etching and diffusion bonding. Experimental results indicate that the heat transfer coefficients were relatively unchanged around 2600 W/m2-K for flow rates ranging from 2–4 g/s while the pressure drop increased monotonically with the flow rate. None of the existing correlations in literature on cross flow over a tube bank or micro pin fin heat sinks were able to predict the experimental pressure drop and heat transfer characteristics. However, three dimensional simulations performed using ANSYS Fluent showed reasonable (∼7 percent difference) agreement in the average heat transfer coefficients between experiments and CFD simulations.

An Experimental Study of Pin Fin Heat Sinks and Determination of End Wall Heat Transfer

2003 ◽  
Author(s):  
Massimiliano Rizzi ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Optimization Methods ◽  
Heat Sinks ◽  
Base Region ◽  
Transfer Coefficients ◽  
Media Type ◽  
Pin Fin ◽  
Heat Transfer Coefficients

An experimental study of a pin fin heat sink was carried out in support of the development of heat sink optimization methods requiring more detailed measurements be made. Measurements of heat flux and temperature are used to separately determine heat transfer coefficients for the pins and the base region between the pins. Three pitch to diameter ratios (distance from pin center to pin center measured diagonally) were studied: P/d = 3/1, 9/4, 3/2. Heat generation was accomplished using cartridge heaters inserted into a copper block. The high thermal conductivity of the copper ensured that the surface beneath the heat sink would be at a constant temperature. The cooling fluid was air and the experiments were conducted with a Reynolds numbers based on a porous media type hydraulic diameter ranging from 500 to 25000. The channel had a shroud that touches the fin tips, eliminating any flow bypass. The pin surface heat transfer coefficients match the values reported by Kays and London and by Zukauskas. The base region heat transfer coefficients were, surprisngly, larger than the pin values.

A Novel Concept to Improve the Performance of LED Panel Using Drilled Holes

2005 ◽  
Author(s):  
S. B. Chiang ◽  
C. C. Wang
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Heat Sink ◽  
Maximum Temperature ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Pin Fins ◽  
Overall Performance ◽  
Novel Concept

In this study, the concept of the thermal module of LEDs cooling by use of drilled hole to entrain air flow was examined. It is found that the drilled hole does not necessarily improve the overall performance. It depends on the size of the drilled hole, the number of drilled holes, and the locations. The heat transfer coefficients are generally increased with the number of drilled holes and the diameter of the drilled hole. In this paper, the plate fin heat sink has a higher heat transfer coefficients than pin fins, but the overall performance of the LED panel having pin fin outperforms that of plate fin. This is because the pin fin provides much larger surface area. For decrease the maximum temperature of the LED panel, placement of the drilled holes along the hot region will be more effective.

Detailed Measurements of End-Wall Heat Transfer Coefficients of Square Pin-Fin Heat Sink for LED Lamp at Forced Convective State

2013 ◽  
Vol 284-287 ◽  
pp. 697-701
Author(s):  
Tzer Ming Jeng ◽  
Sheng Chung Tzeng
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Rectangular Channel ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Wall Area ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Convective State ◽  
End Wall

The device made of fan and pin-fin heat sink should be a powerful heat sink for LED lamp. This study used transient liquid crystal experimentation to measure the end-wall heat transfer coefficient of linearly arrayed square pin array in the rectangular channel, and discussed the influence of axial spacing on heat transfer. The air was used as operating fluid, and the square pin size was 8 mm (d) × 8 mm (d) × 64 mm (Hf), arrayed in a 240 mm (L) × 120 mm (W) × 64 mm (H) rectangular channel. The relative lateral spacing (XT=ST/d) was set as 3, and the relative axial spacing (XL=SL/d=1.88~5) and the Reynolds number (Re=11047~17937) were changed. Considering the end-wall area, the average Nusselt number with square pin was 1.46~2.58 times of that without square pin, and the square pin array of XL= 3.75 had the maximum end-wall heat transfer gain.

scholarly journals Experimental and Cfd Analysis of Heat Transfer Rate in Multi Air Jet Impingement Over A Flat Plate and Pin-Fin Heat Sink

2020 ◽  
Vol 9 (12) ◽  
pp. 329-337
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Heated Surface ◽  
Jet Impingement ◽  
Turbulent Jet ◽  
Transfer Performance ◽  
Pin Fin ◽  
Air Jet

In this paper reports the results of investigation of heat transfer performance of in compression air jet impinging of heated surface over a flat plate & pin-fin heat sink. To mimic the computer processor of flat plate and pin fin dimensions are 120mm*75mm and pin height is 5cm and fin radius is 1cm and L/d ratios are 5,10,15respectively. By using this simulation in Ansys fluent software to perform the turbulent jet impingement on a surface. The bottom surface of the plate is supply constant heat flux and top surface of the plate is cooled by an impingement jet of air. It has two equations are used k-w model and shear stress transport to handle the turbulent jet. The result of flat plate heat sink is compare the Experimental and simulation is higher at 0.89% of experimental to compare numerical and Nusselt is higher at 3.35% of numerical to compare the experimental and heat transfer coefficient is higher at 4.51% of numerical to compare the Experimental and result of pin fin heat sink is compare the Experimental and numerical is higher at 0.23% of experimental to compare the numerical and Nusselt number is higher at 0.71% of numerical to compare the experimental and heat transfer coefficient is higher at 0.88% of numerical to compare the experimental. The effect of L/d ratios of jet impingement over a flat plate and pin fin heat sink on the heat transfer performance of the heated surface of investigated.

scholarly journals Enhanced heat transfer characteristics of conjugated air jet impingement on a finned heat sink

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 279-288 ◽  
Author(s):  
Shuxia Qiu ◽  
Peng Xu ◽  
Liping Geng ◽  
Arun Mujumdar ◽  
Zhouting Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Cooling System ◽  
Flow Characteristics ◽  
Jet Impingement ◽  
Transfer Performance ◽  
Transfer Enhancement ◽  
Air Jet

Air jet impingement is one of the effective cooling techniques employed in micro-electronic industry. To enhance the heat transfer performance, a cooling system with air jet impingement on a finned heat sink is evaluated via the computational fluid dynamics method. A two-dimensional confined slot air impinging on a finned flat plate is modeled. The numerical model is validated by comparison of the computed Nusselt number distribution on the impingement target with published experimental results. The flow characteristics and heat transfer performance of jet impingement on both of smooth and finned heat sinks are compared. It is observed that jet impingement over finned target plate improves the cooling performance significantly. A dimensionless heat transfer enhancement factor is introduced to quantify the effect of jet flow Reynolds number on the finned surface. The effect of rectangular fin dimensions on impingement heat transfer rate is discussed in order to optimize the cooling system. Also, the computed flow and thermal fields of the air impingement system are examined to explore the physical mechanisms for heat transfer enhancement.

MEMS Impinging-Jet Cooling

2000 ◽  
Author(s):  
Qiao Lin ◽  
Shuyun Wu ◽  
Yin Yuen ◽  
Yu-Chong Tai ◽  
Chin-Ming Ho
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Measured Temperature ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Jet Cooling

Abstract This paper presents an experimental investigation on MEMS impinging jets as applied to micro heat exchangers. We have fabricated MEMS single and array jet nozzles using DRIE technology, as well as a MEMS quartz chip providing a simulated hot surface for jet impingement. The quartz chip, with an integrated polysilicon thin-film heater and distributed temperature sensors, offers high spatial resolution in temperature measurement due to the low thermal conductivity of quartz. From measured temperature distributions, heat transfer coefficients are computed for single and array micro impinging jets using finite element analysis. The results from this study for the first time provide extensive data on spatial distributions of micro impinging-jet heat transfer coefficients, and demonstrate the viability of MEMS heat exchangers that use micro impinging jets.

Optimization of Vortex Promoter Parameters to Enhance Heat Transfer Rate in Electronic Equipment

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Ece Aylı ◽  
Özgür Bayer
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Maximum Temperature ◽  
Transfer Coefficients ◽  
Enhance Heat Transfer ◽  
Distance Ratio ◽  
Heat Transfer Coefficients ◽  
Optimization Study ◽  
Finned Surface ◽  
Lower Temperature

Abstract In this paper, optimization of the location and the geometry of a vortex promoter located above in a finned surface in a channel with eight heat sources is investigated for a Reynolds number of 12,500 < Re < 27,700. Heat transfer rates and the corresponding Nusselt number distributions are studied both experimentally and numerically using different vortex promoter geometries (square, circular, and triangular) in different locations to illustrate the effect of vortex promoter on the fluid flow. Optimization study considered a range of following parameters: blockage ratio of 0.30 < (y/C) < 0.45 and interpromoter distance ratio of 0.2277 < (x/L) < 0.3416. Results show that fins over which rectangular and circular promoters are integrated perform better in enhancing the heat transfer. According to the numerical and experimental results, higher blockage ratios cause significantly higher heat transfer coefficients. According to the observations, as the interpromoter distances increase, shedding gains strength, and more turbulence is created. All vortex promoters enhance heat transfer resulting in lower temperature values on the finned surface for different (y/C) and (x/L) values and Reynolds numbers. The use of promoters enhances the heat transfer, and the decrease in the maximum temperature values is recorded on the finned surface changing between 15% and 27%. The biggest decrease in maximum surface temperature value is 500 K–364 K and observed in circular promoter case with (y/C) = 0.43, (x/L) = 0.3416, and Reynolds numbers of 22,200.

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