Pressure Drop in Generating Free-Surface Liquid Microjet Array From Short Cylindrical Orifices

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Avijit Bhunia ◽  
C. L. Chen
Keyword(s):  
Free Surface ◽  
Pressure Drop ◽  
Functional Dependence ◽  
High Heat ◽  
Current Data ◽  
Nonlinear Dependence ◽  
Liquid Jet ◽  
High Heat Flux ◽  
Research Attention ◽  
Surface Liquid

Liquid microjet arrays have received a lot of research attention in recent years due to its high heat flux cooling capability. The microjets are generated from a jet head cavity with a liquid inlet port on one wall and an array of micro-orifices on another wall. An important, yet relatively less studied aspect of the topic is the pressure (also frequently referred to as the pressure drop) necessary to generate the jets and maintain certain jet velocity. In this study we investigate the pressure drop for17 different array patterns of liquid jet issuing in a surrounding gas (air) medium, i.e., a free surface liquid jet. The number of jets varies from 1 to 126, while the jet diameter ranges from 99 to 208 μm. The current results show more than 200% deviation from the existing correlations in the literature. Through a systematic experimental study we identify the functional dependence of pressure drop on the various geometric parameters. The results uncover the reasons behind the widespread disagreement between the current data and the existing correlations. Pressure drop shows a weak, nonlinear dependence on the orifice wall thickness, compared to the linear dependence used in the existing correlations. Furthermore, the depth of the jet head cavity is shown to be an important parameter dictating pressure drop, unlike the previous studies that inherently assume the cavity to be an infinite reservoir. A new dimensionless pressure drop parameter is proposed and its variation with the jet Reynolds number is correlated. The new correlation predicts all the experimental data within a ± 10% range.

Numerical Study of Turbulent Heat Transfer and Pressure Drop Characteristics in a Water-Cooled Minichannel Heat Sink

2006 ◽  
Vol 129 (3) ◽  
pp. 247-255 ◽  
Author(s):  
X. L. Xie ◽  
W. Q. Tao ◽  
Y. L. He
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Wall Thickness ◽  
Heat Sink ◽  
Channel Wall ◽  
High Heat ◽  
Coolant Fluid ◽  
High Heat Flux ◽  
It Industry

With the rapid development of the Information Technology (IT) industry, the heat flux in integrated circuit (IC) chips cooled by air has almost reached its limit at about 100W∕cm2. Some applications in high technology industries require heat fluxes well beyond such a limitation. Therefore, the search for a more efficient cooling technology becomes one of the bottleneck problems of the further development of the IT industry. The microchannel flow geometry offers a large surface area of heat transfer and a high convective heat transfer coefficient. However, it has been hard to implement because of its very high pressure head required to pump the coolant fluid through the channels. A normal channel size could not give high heat flux, although the pressure drop is very small. A minichannel can be used in a heat sink with quite a high heat flux and a mild pressure loss. A minichannel heat sink with bottom size of 20mm×20mm is analyzed numerically for the single-phase turbulent flow of water as a coolant through small hydraulic diameters. A constant heat flux boundary condition is assumed. The effect of channel dimensions, channel wall thickness, bottom thickness, and inlet velocity on the pressure drop, temperature difference, and maximum allowable heat flux are presented. The results indicate that a narrow and deep channel with thin bottom thickness and relatively thin channel wall thickness results in improved heat transfer performance with a relatively high but acceptable pressure drop. A nearly optimized structure of heat sink is found that can cool a chip with heat flux of 350W∕cm2 at a pumping power of 0.314W.

Laminar Flow Forced Convection Heat Transfer Behavior of Phase Change Material Fluid in Microchannels With Staggered Pins

2010 ◽  
Author(s):  
Satyanarayana Kondle ◽  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Gurunarayana Ravi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Phase Change ◽  
Single Phase ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
High Heat ◽  
High Heat Flux ◽  
Small Areas ◽  
Phase Fluid

Microchannels have been extensively studied for electronic cooling applications ever since they were found to be effective in removing high heat flux from small areas. Many configurations of microchannels have been studied and compared for their effectiveness in heat removal. However, there is little data available in the literature on the use of pins in microchannels. Staggered pins in microchannels have higher heat removal characteristics because of the continuous breaking and formation of the boundary layer, but they also exhibit higher pressure drop because pins act as flow obstructions. This paper presents numerical results of two characteristic staggered pins (square and circular) in microchannels. The heat transfer performance of a single phase fluid in microchannels with staggered pins, and the corresponding pressure drop characteristics are also presented. An effective specific heat capacity model was used to account for the phase change process of PCM fluid. Comparison of heat transfer characteristics of single phase fluid and PCM fluid are made for two pins geometries for three different Reynolds numbers. Circular pins were found to be more effective in terms of heat transfer by exhibiting higher Nusselt number. Circular pin microchannels were also found to have lower pressure drop compared to the square pin microchannels.

scholarly journals Conjugated Heat Transfer on a Horizontal Surface Impinged by Circular Free-Surface Liquid Jet.

2002 ◽  
Vol 45 (2) ◽  
pp. 307-314 ◽  
Author(s):  
Yaohua ZHAO ◽  
Takashi MASUOKA ◽  
Takaharu TSURUTA ◽  
Chong-Fang MA
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Horizontal Surface ◽  
Liquid Jet ◽  
Conjugated Heat Transfer ◽  
Surface Liquid

Microbubbles Emission Flow Boiling in a Microchannel and Minichannel

2004 ◽  
Author(s):  
Manabu Tange ◽  
Maki Yuasa ◽  
Shu Takagi ◽  
Masahiro Shoji
Keyword(s):  
Pressure Drop ◽  
Annular Flow ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
High Heat ◽  
Bulk Liquid ◽  
Experimental Investigations ◽  
Channel Height ◽  
High Heat Flux ◽  
Thin Wire

This paper reports the results of experimental investigations on microbubbles emission boiling (MEB) in a microchannel and minichannel. MEB is a boiling phenomenon under high subcool and high heat flux condition. To understand the mechanisms and processes of MEB, pool boiling on a thin wire under subcooled condition was firstly performed. Under various subcooling condition, the experiments of subcool boiling were performed. From photographic observation, distributions of bubble diameters and their dependence on subcooling were investigated. To achieve better understanding of the process of MEB and to find the incipient subcooling of MEB, a sound of ebullition was recorded and analyzed. It was found that 30 to 40 K are the incipient subcooling of MEB on the thin wire. In the experiment of MEB in microchannel and minichannel, the special attention was paid to longitudinal transition of boiling behavior, since bulk liquid temperature increases in short length in case of subcooled flow boiling. Boiling curves for various channel height were obtained from experimental data, and pressure drop through whole channel was measured. In a minichannel, annular flow flushed out the whole channel from the downstream to the upstream and the pressure drop fluctuates, while in a microchannel, flow pattern was divided into two regions: bubbly flow in upstream and annular flow in downstream.

scholarly journals Cooling of High Heat Flux Flat Surface with Nanofluid Assisted Convective Loop: Experimental Assessment

2017 ◽  
Vol 64 (4) ◽  
pp. 519-531 ◽  
Author(s):  
Amir Arya ◽  
Saeed Shahmiry ◽  
Vahid Nikkhah ◽  
Mohamad Mohsen Sarafraz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
High Heat ◽  
High Heat Flux ◽  
Overall Heat Transfer Coefficient ◽  
Cooling Loop ◽  
The Heat Transfer Coefficient

Abstract Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. % = 0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.

Heat Transfer by a Rotating Liquid Jet Impingement Cooling System

2018 ◽  
Author(s):  
Qi Lu ◽  
Siva Parameswaran ◽  
Beibei Ren
Keyword(s):  
Heat Flux ◽  
Cfd Simulation ◽  
Cooling System ◽  
Automatic Transmission ◽  
Jet Impingement ◽  
High Heat ◽  
Liquid Jet ◽  
High Heat Flux ◽  
Impingement Cooling ◽  
Commercial Code

The circular, liquid jet impingement provides a convenient way of cooling surfaces. To effectively cool the devices inside the electric vehicle, a rotating jet impingement cooling system is designed to evaluate the potential of the jet impingement for high heat flux removal. The liquid used for jet impingement is automatic transmission fluid. The jet impingement system consists of a rotating pipe with two nozzles and a cylindrical ring which is attached to the heat source. To reduce the computational loads, first, the CFD simulation for a laminar flow inside the pipe is carried out to estimate the flow velocities at the nozzle exits. Then, the rotating jet impingement cooling of a cylinder with a uniform surface temperature is investigated numerically for stable, unsubmerged, uniform velocity, single phase laminar jets. The numerical simulation using the commercial code is performed to determine the heat flux removal performance over the cylindrical surface. The numerical results are compared with the empirical formula and experimental measurements from the literature. Furthermore, the effects of the Reynolds number and pipe rotation on the jet impingement cooling performance are also investigated.

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