FIELD OF INVENTION
The present invention relates to Orifice device to control liquid flow in Boiler
tubes/Pipes to control, the upstream and downstream of the Orifice device
having zone of flow regularization and tapping port. More particularly, the
invention relates to a process of configurating an improved orifice-based f1owmeasuring
device for measurement of low-liquid flow boiler tube. The invention
further relates to an improved orifice-based device for measuring a low-liquid
flow in a boiler tube.
BACKGROUND OF THE INVENTION
An orifice meter is a conduit, and acts as a flow-barrier to create a pressure
drop. An hour glass is one form of an orifice. A nozzle, venturi or thin sharp
edged orifice can be used for flow restriction. In order to use any of these
devices for measurement it is necessary to empirically calibrate them. The
calibration consists of passing a known flow volume through the meter and
record the readings in order to provide a 'standard' for measuring of any f1owvolume.
Due to the ease of duplication and the simple construction, the thin
sharp edged orifice is adopted as a standard device and extensive calibration
work is done. Thus, the thin edged orifice is widely accepted as a standard
meansof measuring fluids.
Indian Standard IS 14615 (Part 1): 1999 and ISO 5167-1: 1991 (Reaffirmed in
the year 2004) provides that any Orifice device can only be used within specified
limits of tube/pipe size and Reynolds number. Thus, the provision of ISO 5167
restricts the use of a thin-edged orifice device for tube/pipe sizes less than 50
mm or more than 1200 mm or for tube/pipe having liquid flow below Reynolds
numbers 3150.
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US-publication 2004/0209212 discloses a low gas flow in-line orifice assembly
adapted for use with a gas-fuelded. The orifice assembly comprises an elongate
body formed about a longitudinal axis with a first end and a spaced end. A bore
is defined within and extends in the lengthwise direction of the body. The body
of the orifice assembly is constructed and arranged to be removably placed in
fluid communication with a gas supply line feeding the device. But such a device
has limitation for measurement of liquid flow below a particular Reynolds
number.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to propose a process of configurating
an improved orifice-based flow-measuring device for measurement of low-liquid
flow inside the boiler tube, in which a location for placing the device upstream
and downstream of the flow is determined.
Another object of the invention is to propose a process of configurating an
improved orifice-based flow-measuring device for measurement of low-liquid flow
inside the boiler tube, in which the liquid flow constitutes a flow with low
Reynoldsnumber.
A still another object of the invention is to propose a process of configurating an
improved orifice-based flow-measuring device for measurement of low-liquid flow
inside the boiler tube, in which the flow regularization length of the upstream
and downstream flow in respect of the Orifice device is determined.
Yet another object of the invention is to propose an improved orifice-based
device for measuring of low-liquid flow inside the boiler tube, in which the device
is validated by numerical simulation of several low-liquid flow.
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A further object of the invention is to propose an improved orifice-based device
for measuring of low-liquid flow inside the boiler tube, which is enabled to
provide an accurate value of massflow rate of the low fluid flow.
BRIEF DESCRIPTION QF THE ACCOMPANYING DRAWINGS
Figure 1 - Shows a flow regularization zone for low liquid (less Reynolds number)
flow measurement with Orifice device controlling flow in a boiler tube according
to the invention.
Figure 2 - Shows a pressure sensing (tapping) location in the upstream and
downstream for placement of the orifice device according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, firstly a numerical simulation of low liquid flow is
implemented to generate a geometry of an Orifice plate and build a mesh of an
improved low flow orifice device. The liquid flow is further simulated at different
flow parameters by using the improved low flow orifice device, and the resultant
data is validated with physical modeling;
Figure 1 schematically shows and overall length of a flow regularization zone in a
boiler tube for low liquid (less Reynolds number) flow measurement. A hole size
of the Orifice device (1), and a length of the flow regularization zone of the
downstream flow (2) and the upstream flow (3) are determined based on an
analysis of fluid flow in a typical tube/pipe of diameter less than 50 mm or more
than 1200 mm.
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The determined flow regularization zone is introduced on an orifice device, and
whose cross sectional diameter (D) should be 0.45 to 0.60 times of the inlet
tube/pipe diameter (4) of the orifice device (1), the length of the flow
regularization zone at the downstream (2) should be 7.5 to 8.0 times of the inlet
tube/pipe diameter (4) of the orifice device, and the length of the flow
regularization zone at the upstream (3) should be 4.0 to 6.0 times of the inlet
tube/pipe diameter (4) of the orifice device.
Figure 2 shows a pressure sensing (tapping) location at the downstream (3) and
upstream (4) of the orifice device (1). The location of the vena-contracta (5) is
determined based on analysis of fluid flow pattern in a typical tube/pipe. The
diameter of the vena-contracta (5) should be less than that of the orifice device
(1). The pressure sensing (tapping) location of the upstream (4) of the orifice
device should be within the vena-contracta (5). The method of determination of
vena-contracta location should be less or greater than the 0 and 0/2 as
mentioned in the standards.
WE CLAIM
1. A method of measurement of low-liquid flow passing, through an orifice
device in a boiler tube having diameter having diameter below 50 mm or
above 1200 mm, the liquid flow maintaining a Reynolds number below
3150, the method comprising the step of:
- locating a pressure sensor-zone for disposing a measuring device, the
location in respect of the upstream flow (3) and the downstream flow (2)
being determined based on a numerical simulation of the liquid flow below
the Reynold's number of 3150, selecting a location of the vena-contracta
(5) between within the cross-sectional diameter (D) of the liquid flow, the
diameter of the vena-contracta (5) being less than that of the orifice
device; and
- determining a flow-regularization zone in the boiler tube (14) whose
cross-sectional diameter being 0.45 to 0.60 times that of the tube, and
the length of flow-regularization zone being 7.50 to 8.00 times that of the
tube at the downstream (2) of the orifice device (1), and 4.0 to 6.0 times
that of the tube at the upstream (3) of the orifice device (1).
2. An improved orifice-based device in a boiler tube for measuring liquid flow
with Reynold number below 3150, the tube having diameter less than 50
mm, or more than 1200 mm, the device comprising an orifice plate having
at least one hole (1) characterized in that the hole size of the orifice plate
is determined based on a numerical simulation of low liquid flow to create
a geometry corresponding to the diameter of the tube, and Reynold
number of the liquid flow; configurating a mesh of the device based on
the evolved simulation data; further simulating the liquid flow at different
flow parameters; and validating the resultant data with physical modeling.