This study summarizes a fundamental investigation of flow through an array of silicon micromachined rectangular slots. The purpose of the study is to evaluate the effect of entrance pressure, flow area, orifice thickness, slot length, and slot width of the orifice on flow rate. These orifices were fabricated using a simple frontside through wafer DRIE process on a 385 μm thick wafer and wafer bonding to create thicker orifices. The dies were then packaged as part of a TO8 can and flow tested. To complement the results of this experimental work, two simple flow models were developed to predict the effect of geometrical and entrance conditions on the flow rate. These models were based on macroscale assumptions that were not necessarily true in the case of thin orifices. One relationship was based on Pouiselle flow which assumes fully developed flow conditions. Calculation of the entry length required for fully developed flow indicate that in the low Reynolds Number regime (32-550) evaluated, the entry flow development requires 2-8 times the thickness of the thickest orifices used for this study. Therefore, calculations of orifice flow based on a Pouiselle model are an overestimate of the actual measured flow rates. Another model examined typical orifice relationships using head loss at the entrance and exit of the slots did not accurately capture the particular flow rates since it overestimated the expansion or constriction losses. A series of experiments where the pressure was varied between 75 and 1000 Pa were performed. A comparison of the Pouiselle flow solution with experimental results was made which showed that the Pouiselle flow model overpredicts the flow rates and more specifically, the effect of width on the flow rates. The results of these tests were used to develop a transfer function which describes the dependence of flow rate on orifice width, thickness, length, and inlet pressure.

1.
Turner
S. E.
,
Lam
L. C.
,
Faghri
M.
, and
Gregory
O. J.
,
2004
, “
Experimental Investigation of Gas Flow in Microchannels
,”
Journal of Heat Transfer
,
126
, pp.
753
763
.
2.
Guo
Z.-Y.
and
Li
Z.-X.
,
2003
, “
Size Effect on Microscale Single-Phase Flow and Heat Transfer
,”
International Journal of Heat and Mass Transfer
,
46
, pp.
149
159
.
3.
Papautsky, I., Ameel, T., and Frazier, A. B., 2001, “A review of Laminar Single-Phase flow in Microchannels,” Proceedings of the 2001 ASME IMECE, November 11–16, 2001, New York.
4.
Alexeenko
A. A.
,
Gimelshein
S. F.
, and
Levin
D. A.
,
2005
, “
Reconsideration of Low Reynolds Number Flow-Through Constriction Microchannels Using the DSMC Method
,”
Journal of Microelectromechanical Systems
,
14
, No.
4
, pp.
847
56
.
5.
Lee
W. Y.
,
Wong
M.
, and
Zohar
Y.
,
2002
, “
Pressure Loss in Constriction Microchannels
,”
Journal of Microelectromechanical Systems
,
11
, No.
3
, pp.
236
44
.
6.
Lee
W. Y.
,
Wong
M.
, and
Zohar
Y.
,
2002
, “
Microchannels in Series Connected Via a Constriction/Expansion Section
,”
Journal of Fluid Mechanics
, No.
459
, pp.
187
206
.
7.
Munson, B.R., Young, D.F., and Okiishi, T.H., Fundamentals of Fluid Mechanics, John Wiley & Sons, Inc., New York.
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