Entrance and Exit Losses for Developing Flow in Parallel Plate Channels

Webb, Ralph L.

doi:10.1080/01457630600904650

Cited by 13 publications

(4 citation statements)

References 3 publications

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“…In the entrance region a stronger pressure drop is evident, in particular for the highest flow rates. As discussed by Webb [2], this behavior can be explained by the further decrease of static pressure due to the recirculation of the fluid close to the wall of the duct in the sudden contraction of the passage area (vena contracta).…”

Section: Resultsmentioning

confidence: 90%

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Experimental Investigation of the Fluid Dynamics of a Finned Heat Sink under Operating Conditions

Casano¹,

Collins²,

Piva³

2014

JECTC

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An experimental study has been made of the fluid dynamics performance of electronic equipment designed to cool a heat sink in the form of a finned duct. The apparatus consists of a channel of rectangular section containing the finned duct. A forced airflow is driven by three fans placed in parallel in the inlet and in the outlet sections of the channel. In order to investigate a full range of flow rates, different sets of fans were used in the inlet section. Measurements were made of static pressures at different channel positions by pressure taps connected to a micro manometer, and of the flow rate by a Venturi meter. The experimental working conditions of the active fans were consistent with the manufacturers’ characteristic curves. Values of the local friction coefficient compared well with published correlations. The experimental working points agreed very well with the theoretical curve of the pressure drop and the hydraulic diameter was demonstrated to be of the appropriate size for this fluid dynamics problem

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Section: Resultsmentioning

confidence: 90%

“…Since in these applications the length of the heat sink is never of particular importance, the inlet and outlet regions tend to become significant relative to the total length of the duct. This situation has been discussed in depth by Webb [2].…”

Section: Introductionmentioning

confidence: 96%

Experimental Investigation of the Fluid Dynamics of a Finned Heat Sink under Operating Conditions

Casano¹,

Collins²,

Piva³

2014

JECTC

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“…Entrance effects due to hydrodynamic and thermal development are very effective in short microchannels and significantly affect the pressure drop and heat transfer coefficient values. Webb [3] stated that for short channels, the portion of pressure drop due to the entrance and exit losses may be as high as 30% of the total pressure drop in the device. Ali et al [4] experimentally investigated the single phase heat transfer and pressure drop in the rectangular microchannel in which the surface was coated with copper nanowires by electrochemical synthesis technique.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Single-Phase Heat Transfer on Scalable Nanostructured Microchannels

Behera¹,

Mohanty²,

Ghosh³

et al. 2018

World Congress on Mechanical, Chemical, and Material Engineering

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In this paper, the thermal performance of nanostructured (CuO nanostructures) copper multiple parallel microchannels for single-phase flow is studied. The test section consists of 6 parallel channels and each channel is 350 µm wide and 605 µm deep with an aspect ratio of 1.729. Microchannels are covered on the top surface with an acrylic sheet. A cartridge heater is inserted at the bottom of the microchannels for supplying the desired heat flux and the position of the heater is determined numerically. Deionized water (DI) is used as the working fluid in the experiment. Single-phase pressure drop and heat transfer coefficient in multiple nanostructured microchannels are measured. A maximum enhancement of ~21% in Nusselt number is reported without any observable increase in pressure drop upon the incorporation of nanostructured in microchannels. The current study could provide a suitable low-cost framework for investigating the potential of nanostructures in further enhancement of single phase heat transfer coefficients in microchannel geometry.

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“…However, in PC or server applications, the small fin spacing will cause significant pressure loss in the entrance or exit of heat sink due to contraction and expansion. In coping with the entrance and exit losses for developing flow in parallel plate channels, Kays and London [25] and Webb [54] had proposed correlations for inlet K i and outlet K o loss coefficients for parallel plate channels. Notice that inclusion of the entrance and exit loss for accurate estimation of the flow impedance is essential since the size of the air-cooled heat sink is normally small.…”

Section: Augmentation Via Materials Savingmentioning

confidence: 99%

A Quick Overview of Compact Air-Cooled Heat Sinks Applicable for Electronic Cooling—Recent Progress

Wang

2017

Inventions

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Abstract:This study provides an overview regarding enhancement of an air-cooled heat sink applicable for electronic cooling subject to cross-flow forced convection. Some novel designs and associated problems in air-cooled heat sinks are discussed, including the drawback of adding surfaces, utilization of porous surfaces such as metal foam or carbon foam, problems and suitable applicable range of highly interrupted surfaces (louver or slit) and longitudinal vortex generator. Though the metal foam may accommodate significant surface area, it is comparatively ineffective for air-cooling application due to its much lower fin efficiency, and this shortcoming can be improved by integrating with solid fin. For highly dense fin spacing (e.g., <1.0 mm), cannelure or grooved surface may be a better choice, and fin structure with periodic contraction and expansion may not be suitable for it introduces additional pressure drop penalty. The partial bypass concept, which manipulates a larger temperature difference at the trailing part of heat sink, can be implemented to significantly reduce the pressure drop. Through some certain niche operation, t the thermal resistance of the partial bypass heat sink may be superior to the conventional heat sink. The trapezoid fin surface featuring easier manufacturing and a smaller weight is shown to have competitive performance against traditional rectangular fin geometry. The IPFM (Interleaved Parallelogram Fin Module) design which combines two different geometrical fins with the odd number fins being rectangular shape, and parallelogram shape in even fin numbers, shows 8%-12% less surface than conventional design but still offers a lower thermal resistance than the conventional rectangular heat sink in lower flowrate operation. The cross-cut design shows appreciable improvements as compared to the conventional plate fin design especially in high velocity regime and the single cross-cut heat sinks are superior to multiple cross-cut heat sinks.

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Entrance and Exit Losses for Developing Flow in Parallel Plate Channels

Cited by 13 publications

References 3 publications

Experimental Investigation of the Fluid Dynamics of a Finned Heat Sink under Operating Conditions

Experimental Investigation of the Fluid Dynamics of a Finned Heat Sink under Operating Conditions

Experimental Investigation of Single-Phase Heat Transfer on Scalable Nanostructured Microchannels

A Quick Overview of Compact Air-Cooled Heat Sinks Applicable for Electronic Cooling—Recent Progress

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