Flow restrictor and system for delivering a flow of liquid...

Details Flow restrictor and system for delivering a flow of liquid... Flow restrictor and system for delivering a flow of liquid...

2004-09-04

2008-10-07

Bastianelli, John (Department: 3753)

Pipes and tubular conduits

With flow regulators and/or baffles

Restrictors

C251S118000, C604S246000

Reexamination Certificate

active

07431052

ABSTRACT:
The present invention relates to apparatus for delivering a controlled or restricted flow of liquid and limiting bubble fragmentation at the inlet. This is achieved in flow restrictor with a flow channel having over most of its length a substantially constant, minimum hydraulic diameter D=4A/W wherein A is the minimum local cross-sectional area of the channel and W is the minimum local wetting perimeter of the channel, by smoothly widening the channel at its inlet such that:at distances z from the inlet face with 0<z<z1, the channel has a hydraulic diameter Dz≧k*D wherein k≧1.3;at distances z from the inlet face with z1<z<z2, the channel has a hydraulic diameter Dzwith k*D≧Dz≧D; andat distances z from the inlet face with z2<z, the channel has a hydraulic diameter Dzwith Dz≦1.02D, except possibly for a similar widening of the channel at the outlet. It has been found that widening the flow channel at the inlet, such that its diameter increases smoothly and gradually, and preferably by a factor of at least 1.3 over a length of at least 3 channel diameters, significantly reduces the tendency towards bubble fragmentation in microcapillary flow restrictors, and also substantially increases the yield of devices which operate well.

REFERENCES:
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Article entitled “The clogging pressure of large bubbles in microchannel contractions” by M. Jensen et al., Mikroelektronik Centret (MIC), Technical University of Denmark, Jun. 7, 2003, pp. 1-22.
Article entitled “Quasi-static Motion of Bubbles in Microchannel Contractions” by M. Jensen et al., Mikroelektronik Centret (MIC), Technical University of Denmark, undated, pp. 1-4.
Article entitled “A capillary suction probe for bubble size measurement” by M. Barigou et al., Measurement Science & Technology, Apr. 2, 1991, No. 4, Bristol, GB, pp. 318-326.

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