Plates perforated with venturi-like orifices

Plates that are perforated with two or more venturi orifices that have "C.sub.d " discharge coefficient values that are greater than 1.0. The venturi orifices to be used can be made in an infinite number of tubes that have a converging entrance, a throat, and a diverging discharge. The plates are to be used to make improved devices to be used in fluid flow streams.

BACKGROUND 
1. Field of Invention 
This invention relates to devices used in fluid flow streams. Devices such 
as fluid distributor plates, filters, heat exchangers, valves, and flow 
metering plates. 
2. Description of Prior Art 
A variety of devices are used in fluid flow streams for filtering, 
controlling, exchanging heat, metering, and such. All such devices 
necessarily impede the flow to some extent. In forced flow streams such 
devices decrease pressure energy. Minimizing all such energy losses is 
desirable. 
The invention herein described relates to the manufacture of plates that 
are perforated with two or more venturi orifices. The venturi orifices are 
to have "C.sub.d " discharge coefficient values that are greater than 1.0. 
"C.sub.d " is the discharge coefficient that is used in the flow formula 
for nozzles and orifices. 
The flow formula referred to above and others are to be introduced 
hereinafter. Formulas are required to show that "C.sub.d " values greater 
than 1.0 have been implied by past patents that have been granted. 
Textbooks on fluid flow present the following Bernoulli Equation for 
steady, frictionless, incompressible flow: 
EQU P.sub.1 /.rho..sub.1 +v.sub.1.sup.2 /2g+z.sub.1 =P.sub.2 /.rho..sub.2 
+v.sub.2.sup.2 /2g+z.sub.2 
where 
P.sub.1 =initial pressure, lb per ft.sup.2 
.rho..sub.1 =initial specific weight, lb per ft.sup.3 
v.sub.1 =initial velocity, ft per sec 
g=32.2 ft per sec.sup.2 
z.sub.1 =initial elevation with reference to some base elevation, ft 
Any subsequent condition is P.sub.3, z.sub.3, etc. 
All terms of the Bernoulli Equation result in feet of the fluid. The first 
term is called pressure head. The second term is called velocity head. The 
last term is called potential head. 
Deriving formulas is simplified by making logical, practical, and 
acceptable assumptions. Assuming incompressible flow means that the 
specific weight does not change significantly over the range of conditions 
to be investigated. Thus, hereinafter, .rho..sub.1 =.rho..sub.2 
=.rho..sub.3 =.rho.. Likewise, assume that the centerline of all flow 
streams are level. Thus, z.sub.1 =z.sub.2 =z.sub.3. So that the potential 
head terms will be dropped from the Bernoulli Equation used hereinafter. 
Picture a still tank of some incompressible fluid with a perfect hole in 
its side at "h" feet below its surface. So that P.sub.1 =h.rho.. For the 
still tank v.sub.1 =0. Neglecting insignificant air pressure differences, 
P.sub.2 =0. Some of the fluid will emerge at a velocity of v.sub.2. 
So that 
EQU P.sub.1 /.rho.=v.sub.2.sup.2 /2g=h.rho./.rho.=h 
Resulting in 
EQU v.sub.2 =.sqroot.2gh 
If the area of the theoretically perfect jet stream described above is 
A.sub.2, ft.sup.2, the rate of discharge is exactly: 
EQU Q=A.sub.2 v.sub.2, ft.sup.3 per sec 
In this real world, the theoretically perfect is not possible. If a real 
nozzle were made in the tank wall as presumed above, the real discharge 
velocity would be in the range of 90% to 99% of the theoretical velocity. 
This introduces the concept of "C.sub.d " called the discharge 
coefficient. "C.sub.d " accounts for non-uniformity of velocity in the 
inlet and discharge, the rate of flow, fluid viscosity, and surface 
roughness. "C.sub.d " is preferably determined by actual measurement that 
is called calibration. So that the real rate of discharge is calculated by 
: 
EQU Q=C.sub.d A.sub.2 v.sub.2, ft.sup.3 per sec 
Therefore, for nozzles discharging from a large space or plenum chamber, 
the value of "C.sub.d " is usually measured to be in the range of 0.90 to 
0.99. Note that "C.sub.d " cannot be greater than 1.0 for nozzles. 
If a circular sharp edged orifice is made in the tank wall presumed above, 
the real discharge rate is measured to be much lower than the theoretical 
rate. The primary reason for the much lower rate is that the fluid flow 
stream emerging from the sharp edged orifice contracts in cross sectional 
area. A coefficient of contraction is therefore measured to account for 
the reduction of the area of the orifice to that of the smallest area. 
This coefficient of contraction is usually measured to be in the range of 
0.61 to 0.72. There is a further loss measured that is called the 
coefficient of velocity to account for friction losses that reduce the 
velocity in the smallest area from the theoretical velocity. The 
coefficient of velocity is usually measured to be in the range of 0.95 to 
0.99. Thus, "C.sub.d " for circular sharp edged orifices is equal to the 
product of the coefficient of contraction and the coefficient of velocity. 
Note that "C.sub.d " cannot be greater than 1.0 for circular sharp edged 
orifices. 
Nozzles, orifices, and venturi tubes are installed into mostly round pipe 
lines and ducts to measure flow rates. Now the entrance velocity may be of 
some significant value. The flow in equals the flow out, i.e., Q.sub.1 
=Q.sub.2. So that: 
EQU Q.sub.1 =A.sub.1 v.sub.1 =A.sub.2 v.sub.2 =Q.sub.2 
Back to the Bernoulli Equation, but this time v.sub.1 =A.sub.2 v.sub.2 
/A.sub.1, and the outlet pressure P.sub.2 may now have some value. 
So that 
EQU P.sub.1 /.rho.+(A.sub.2 v.sub.2 /A.sub.1).sup.2 /2g=P.sub.2 
/.rho.+v.sub.2.sup.2 /2g 
Resulting in 
EQU (P.sub.1 -P.sub.2)/.rho.=v.sub.2.sup.2 /2g1-(A.sub.2 /A.sub.1).sup.2 ! 
Now the real rate of discharge is calculated by: 
##EQU1## 
Textbooks call the ratio of the throat diameter to the inlet diameter 
Beta. So that: 
EQU .beta.=d.sub.2 /d.sub.1 or .beta..sup.4 =(d.sub.2 /d.sub.1).sup.4 =(A.sub.2 
/A.sub.1).sup.2 
By substitution: 
##EQU2## 
Textbooks publish "C" flow coefficient values for orifices and nozzles 
where: 
##EQU3## 
"C" values for nozzles and orifices are reported above 1.0 when the value 
of Beta is large enough. "C" values are not to be confused with "C.sub.d " 
values. Nozzles, orifices, wire mesh screens, straight perforations, and 
such cannot have "C.sub.d " discharge coefficient values greater than 1.0. 
The diverging discharge sections of venturi tubes that are designed for 
flow measurement with minimum pressure drop are made to restore the 
discharge pressure as nearly as possible to the inlet pressure. Some 
overall "C.sub.d " values can be calculated for such metering tubes that 
are marketed. See FIG. 4 of U.S. Pat. No. 4,174,734, to Bradham, (1979). 
Note that the ALLEN FLOW TUBE is shown as losing about 2.9% of the 
differential pressure at a Beta=0.75. Since no other data is given, it 
will be assumed here that the said flow tube had a "C.sub.d "=0.98 for the 
inlet to throat portion. The overall "C.sub.d " will be based upon the 
state measurement where (P.sub.1 -P.sub.3)=0.029 (P.sub.1 -P.sub.2), where 
P.sub.3 is the outlet pressure. The overall "C.sub.d " value will be based 
upon the throat area A.sub.2 since that is the standard for nozzles and 
orifices. Therefore: 
##EQU4## 
Which reduces to 
EQU 0.98=C.sub.d .sqroot.0.029 
Resulting in 
EQU C.sub.d =5.75 
Likewise, from said FIG. 4, that for a LO-LOSS metering tube, that about 
3.05% is the differential pressure loss at Beta=0.75. 
This results in 
EQU 0.98=C.sub.d .sqroot.0.0305 
So that 
EQU C.sub.d =5.61 
Again, from said FIG. 4, that for a UNIVERSAL FLOW TUBE that about 3.45% is 
reported as the differential pressure loss at a Beta=0.75. 
Thus 
EQU 0.98=C.sub.d .sqroot.0.0345 
So 
EQU C.sub.d =5.28 
Likewise, from said FIG. 4, that a VENTURI-LONG FORM is reported as having 
about 11.25% differential pressure loss at a Beta=0.75. 
This results in 
EQU 0.98=C.sub.d .sqroot.0.1125 
So that 
EQU C.sub.d =2.92 
Lastly, from said FIG. 4, that a VENTURI-SHORT FORM is reported as having 
about 11.10% differential pressure loss at a Beta=0.75. 
Now 
EQU 0.98=C.sub.d .sqroot.0.1110 
So 
EQU C.sub.d =2.94 
OBJECTS AND ADVANTAGES 
Venturi tube metering devices are preferred for flow measurement over 
nozzles and orifices because they use less energy to measure the same 
flow. The reason for this improvement is that the diverging section of the 
venturi tube is designed to convert as much as possible of the fluid 
velocity energy that is leaving the venturi throat section back into 
pressure energy at the exit of the diverging section. 
The flow formulas and "C.sub.d " values presented in the previous section 
"Background--Description of Prior Art" can be used to show the relative 
magnitude of the potential energy savings involved in the use of a venturi 
tube in preference to a flow nozzle to measure flow. 
To make comparison easier, assume that "C.sub.d "=1.0 for a perfect flow 
nozzle and a "C.sub.d "=3.0 for a comparable venturi tube. Now, for the 
first and easiest comparison, start with all other conditions being equal, 
i.e., the discharge area of the nozzle is the same as the throat area of 
the venturi tube; the same Beta value is used; the same fluid is flowing; 
and that the pressure loss for the flow nozzle (P.sub.1 -P.sub.2) is the 
same as the overall pressure loss for the venturi tube (P.sub.1 -P.sub.3). 
The discharge rate for the venturi tube will calculate to be three (3) 
times the discharge rate for the flow nozzle because the "C.sub.d " value 
is three (3) times greater. 
Another informative comparison can be made for the venturi tube versus the 
flow nozzle by changing conditions so that the same discharge rate can be 
calculated for both. The easiest change to be envisioned in this regard is 
to assume that the area of the venturi throat is only one-third (1/3) the 
area of the flow nozzle discharge area. With all other conditions being 
equal as assumed previously, except that the "C.sub.d " value is three (3) 
times greater for the venturi tube, the discharge rates for both will 
calculate to be the same. Thus, for the same pressure loss, the venturi 
tube throat area need only be one-third (1/3) the discharge area of the 
flow nozzle. 
The relative magnitude of the potential energy savings can now be shown for 
the above venturi tube versus the flow nozzle comparison by changing the 
pressure loss terms while leaving all the other terms as equal. Now assume 
that the venturi tube pressure loss (P.sub.1 -P.sub.3) is only one-ninth 
(1/9) that of the flow nozzle pressure loss (P.sub.1 -P.sub.2). Note that 
the pressure loss term is under the square root symbol. The square root of 
one-ninth (1/9) is one third (1/3), i.e., .sqroot.1/9=1/3. So that with 
only one-ninth (1/9) of the flow nozzle pressure loss for the venturi 
tube, the discharge rates for both will calculate to be the same. Thus, a 
venturi tube will consume only one-ninth (1/9) the pressure energy that 
would be consumed by a comparable flow nozzle. This energy savings goes on 
day after day, amounting to considerable energy cost savings over the 
years. 
Now to compare the venturi tube performance to that of the sharp edged 
orifice that was presented in the previous section 
"Background--Description of Prior Art". As before, assume that the 
"C.sub.d " value for the venturi tube is equal to three (3). The very best 
"C.sub.d " value that can be calculated from the data given for a sharp 
edged orifice is: 
EQU C.sub.d =0.72.times.0.99=0.71 
Using the same logic as was used above for the venturi tube versus the flow 
nozzle, it develops that the venturi tube uses only one-eighteenth (1/18) 
of the energy used by the very best of the sharp edged orifices. 
Now the "C.sub.d " value for the worst of the sharp edged orifices that can 
be calculated from the data given previously is: 
EQU C.sub.d =0.61.times.0.95-0.58 
So, using the same logic as was used for the venturi tube versus the flow 
nozzle, it develops that the venturi tube uses only one-twenty seventh 
(1/27) of the energy used by the worst of the sharp edged orifices. 
The energy savings of venturi tubes over wire mesh screens and sheets that 
are perforated with straight holes of whatever cross section, mostly fall 
within the range of the one-eighteenth (1/18) to one-twenty seventh (1/27) 
of the energy losses as presented above for the sharp edged orifices. 
Plates that are perforated with venturi orifices are to be preferred for 
their energy saving characteristic. 
Further objects and advantages of using plates that are perforated with 
venturi orifices to make improved devices to be used in fluid flow streams 
will become apparent from a consideration of the ensuing description and 
summary.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a longitudinal view of the basic venturi orifice having a 
converging entrance, a throat, and a diverging discharge. The preferred 
embodiment of the venturi orifice is proportioned similar to the standard, 
Herschel-type venturi meter. The ranges of the included angles and the 
ranges of the lengths of the parts are wider for the venturi orifices of 
the preferred embodiment than those usually employed in the standard, 
Herschel-type venturi meter because objectives other than flow measurement 
with the least pressure loss are considered as described in the section 
"Summary, Ramifications, and Scope" that follows. The inlet opening at the 
face 1 converges to a throat 2 that diverges to a discharge outlet at the 
face 3. The following section "Subscription Numerals" uses "1" for 
conditions at the inlet, "2" for conditions at the throat, and "3" for 
conditions at the discharge. Thus, "D.sub.1 " is the relative diameter of 
the inlet opening, "D.sub.2 " is the relative diameter of the throat, and 
"D.sub.3 " is the relative diameter of the outlet opening. 
FIG. 2a shows the conventional circular cross-sectional view that is 
presented in technical books. FIG. 2b shows a squarish cross-sectional 
view. FIG. 2c shows a triangular cross-sectional view. FIG. 2d shows an 
elliptical cross-sectional view. FIG. 2e shows a six-sided cross-sectional 
view. FIG. 2f shows a cross-section representing some other geometric 
construction. The cross-sectional view II--II is shown at various 
locations to show that the cross-section of venturi orifices of the 
preferred embodiment change any number of times from the inlet to the 
outlet as best suited for the application. 
FIG. 3a shows the conventional straight centerline for a venturi orifice 
that is presented in technical books. FIG. 3b shows a venturi orifice 
centerline that is a bent straight line. FIG. 3c shows a curved venturi 
orifice centerline. FIG. 3d shows a venturi centerline inclined at some 
angle other than 90.degree. to the plate surface. FIG. 3e shows a venturi 
orifice centerline that is partly straight and partly curved. 
FIG. 4a shows the cross-sectional view of a flat plate of uniform thickness 
that is perforated with venturi orifices. FIG. 4b shows the 
cross-sectional view of a plate of variable thickness that has been 
perforated with venturi orifices. 
FIG. 5a shows a plate perforated with venturi orifices that has the 
conventional flat and parallel surfaces that is presented in technical 
books. FIG. 5b shows a flat plate that has been bent. FIG. 5c shows a 
plate with a concave surface. FIG. 5d shows a plate with a convex surface. 
FIG. 5e shows a plate perforated with venturi orifices that has a variable 
surface. 
FIG. 6a shows a triangular layout of venturi orifices on the surface of 
plates to be perforated with venturi orifices. FIG. 6b shows a squarish 
layout. FIG. 6c shows a layout in a circular design. FIG. 6d shows a 
linear layout of venturi orifice centerlines on the surface of plates to 
be perforated with venturi orifices. FIG. 6e shows a non-linear layout. 
FIG. 6f shows a layout of venturi orifice centerlines on the surface of 
plates to be perforated that is of some chaotic form. 
SUBSCRIPTION NUMERALS 
The subscription numerals presented in the section "Background--Description 
of Prior Art" is to be the same throughout this patent application. The 
subscription "1" is used for conditions at the inlet of whatever. The 
subscription "2" is used for conditions at the discharge of flow nozzles, 
or at orifice openings, or at the throat of venturi tubes or venturi 
orifices. The subscription "3" is used for conditions at the discharge of 
venturi tubes or venturi orifices. 
DESCRIPTION 
The inlet area, A.sub.1, of a venturi orifice will always be greater than 
its throat area, A.sub.2. The outlet area, A.sub.3, of a venturi orifice 
will always be greater than its throat area, A.sub.2. The inlet area, 
A.sub.1, may be smaller than the outlet area, A.sub.3, the same as 
A.sub.3, or it may be greater than A.sub.3. 
In normal service, the outlet pressure, P.sub.3, will always be less than 
than the inlet pressure, P.sub.1. 
The outlet velocity, v.sub.3, of most venturi orifices to be used will be 
less than the throat velocity, v.sub.2. However, for some special 
applications, the outlet velocity, v.sub.3, could be designed to be 
greater than the throat velocity, v.sub.2. 
The centerlines of the venturi orifices can be straight, bent, curved, 
inclined, spiralled, or any combination of these. 
The cross-sectional area of the venturi orifices to be used can be of any 
geometrical construction that can be made using straight lines, circles, 
ellipses, polygons, or segments. 
The cross-sectional area can change any number of times from the inlet to 
the outlet. 
The venturi orifices to be used have no passage or passages to the throat 
section. 
The plates to be perforated with venturi orifices can be of uniform 
thickness or of variable thickness. Said plates can be flat, concave, 
convex, rounded, or of any surface that is best suited to the application. 
The layout of the venturi orifice centerlines can be of any regular or 
irregular design from triangular, square, circular, linear, non-linear, or 
of any chaotic form. 
OPERATION 
Valves of various shapes and sizes will be designed using the plates 
perforated with venturi orifices with shields that veil or unveil the 
number of venturi orifices that are exposed to the fluid to be controlled. 
SUMMARY, RAMIFICATIONS, AND SCOPE 
The "C.sub.d " values that were derived in the section 
"Background--Description of Prior Art" are not exact and lack much in 
scientific explanation. However, the tendency of form for the venturi 
orifices will be towards those forms that indicate the higher "C.sub.d " 
values. Obviously, the shorter forms can be produced in thinner plates, 
but no form is ruled out. 
Further advantage in this regard can be made by assuming that a desired 
venturi orifice of a certain required length with a straight centerline, 
such a venturi orifice could be made in a thinner plate if the centerline 
was inclined at some angle other than being perpendicular to the surfaces 
of the plate. 
Obviously, from the section "Background--Description of Prior Art" that 
"C.sub.d " values greater than 3.0 can be expected which would further 
enhance the energy savings for venturi orifices over the other devices now 
marketed. However, "C.sub.d " values less than 3.0 should be anticipated 
for the very small venturi orifices. Likewise, however, it should also be 
anticipated that the "C.sub.d " values for the smaller openings of the 
other devices will decrease as well. So that the relative energy saving 
estimates made in the section "Objects and Advantages" will still prevail. 
The diverging discharge sections of venturi tubes that are made for flow 
measurement with minimum pressure loss are designed to restore the outlet 
pressure, P.sub.3, as nearly as possible to the inlet pressure, P.sub.1. 
Such is not the case for the venturi orifices that are intended herein. 
The venturi orifices to be used will be designed to have the higher 
"C.sub.d " discharge coefficient values for whatever application. For 
example, to design a venturi orifice to be installed in the tank wall 
introduced in the section "Background--Description of Prior Art", to 
restore the outlet pressure, P.sub.3, to nearly that of the inlet 
pressure, P.sub.1, would be wasteful because the outlet pressure energy 
would just be lost at the discharge. A greater discharge rate would be 
obtained by designing the above venturi orifice for a discharge pressure 
P.sub.3 =0. 
The outlet pressure, P.sub.3, for the venturi orifices to be used will only 
be designed to be greater than the inlet pressure, P.sub.1, for those 
cases and times when reversed flow may be desired as for the backwashing 
of strainers and filters. Obviously, whenever P.sub.3 =P.sub.1 that there 
will be no flow. 
There is no reason for the cross-sectional area of venturi orifices to be 
limited to circles. Actual measurement of "C.sub.d " values for 
cross-sections of other geometrical constructions may be less but may 
prove to be more advantageous for packing, the materials of construction, 
or whatever. 
A good example for changing the cross-section of venturi orifices is the 
case for plates perforated with them to serve as strainers or filters. The 
throat area, A.sub.2, to be used will be governed mostly by the size of 
the solid particles to be strained or filtered. Desire for the lowest 
pressure drop leads to maximizing the number of venturi orifices into each 
unit of surface area. One of the more logical of inlet or discharge 
cross-sections to use would be a hexagon. 
Another practical example for changing the cross-sectional area would be 
layout designs for heat exchangers. A linear lineup of the venturi orifice 
centerlines might best serve the heat exchange surface to be used at the 
discharge. For this purpose, one of the more logical cross-sections to use 
would be rectangular to permit closer spacing of the orifice centerlines. 
Plates perforated with venturi orifices will be used to make fluid 
distributor plates. Fluid distributor plates are the bottoms of containers 
of fluid beds through which passes some or all of the fluids that fluidize 
the solid particles of the fluid bed. The layout of the venturi orifice 
centerlines will be designed to best serve the fluid bed being supported 
and fluidized. 
One practical example is for a layout of venturi orifices to pass gases 
into a fluid bed designed to have bubbles of gases that rise through the 
solid particles, usually growing in size as they rise, and burst at the 
top of such bubbling fluid beds. The center to center distance of such gas 
entry ports is set to avoid premature bubble growth by merger of bubbles 
that are being created above adjacent ports. Therefore, the usual practice 
is to maximize the number of ports in each unit of surface while 
maintaining the set center to center spacing. Thus, the usual practice is 
to use a triangular pattern, whereby the centers of three (3) adjacent 
ports are the vertices of an equilateral triangle whose sides are the 
length of the set distance. 
Most fluid beds have some heat exchange surface immersed in them for 
temperature control. Now, where some heat exchange surface is placed above 
a fluid distributor plate, the layout of the venturi orifices might be 
linear, spiralled, or of some other pattern that is best suited to the 
design. The layout of the venturi orifices in the spaces between the heat 
exchanger layout could be of any geometric design. Thus, the layout can be 
of any regular, irregular, or of any chaotic pattern. 
Fluid beds are used to serve many useful purposes. Fluid bed heat 
exchangers use fluidized solid particles to increase heat transfer. Fluid 
bed combustors are used to burn fuels. Fluid bed reactors are used to 
obtain more complete chemical reactions between solids and fluids. Many 
fluid beds are used to mix solids. Fluid bed conveyors are built to move 
solid particles in a fluidized state. Some fluid beds are made of solid 
particles that melt onto or chemically react with the surface of an 
immersed object to effect a coating such as plastic coated trays or 
frames. Fluid distributor plates will be designed to best serve whatever 
kind of fluid bed that is to be contained in whatever kind of container. 
Thus, the plates perforated with venturi orifices can be of uniform or of 
variable thickness and can be flat, concave, rounded, or of any surface 
that is best suited to the application. 
Patented venturi meters for flow measurement have a passage or passages to 
the throat section to measure the pressure there. Patented flow 
restricting devices have a passage or passages to the throat section to 
measure or use the pressure there. The venturi orifices to be used have no 
passage or passages to the throat section. 
The venturi orifices to be used are not like any jet pump, carburetor, 
aspirator, or ejector, in that no attempt is made to conduct a fluid into 
the throat section. 
So called "cavitating venturies" are marketed as flow limiting devices. 
These devices reduce the throat pressure to the point where the flowing 
liquid flashes into a gas. Thus, the flow rate is limited by the pressure 
and properties of the fluid. The venturi orifices to be used will always 
be designed to avoid flashing or cavitation. 
So called "critical flow nozzles" or "sonic chokes" are marketed to limit 
flow by having critical flow occur. Critical flow occurs at sonic 
velocity. Sonic velocity is the speed of sound in the fluid at some 
specific condition. In all applications, critical flow is to be avoided in 
the venturi orifices to be used. 
Although the description above contains many specificities, these should 
not be construed as limiting the scope of the invention. For example, some 
fluid beds now in service use pipes with drilled holes that are installed 
just above a solid flat bottom to introduce the gases for fluidizing the 
solid particles. Now, instead of drilled holes, these gas supply pipes 
could be made using venturi orifices. Such gas supply pipes are to be 
considered as fluid distributor plates even though they really do not 
support the fluid bed. 
Thus the scope of the invention should be determined by the appended claims 
and their legal equivalents, rather than by the examples given.