Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-12-08
2001-06-19
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S050000, C702S138000, C073S861000
Reexamination Certificate
active
06249748
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for determining a flow rate, and more particularly to an apparatus and a method for determining a flow rate of a fluid substance discharged from a reserving device.
BACKGROUND OF THE INVENTION
Conventionally, the process of a fluid substance discharged from a reservoir is controlled by a valve for providing the fluid substance at the specific time, and it is widely used in the industry. For example, a dust collector with a bag filter takes advantage of high pressure air discharged from a reservoir to clean the dust on a filter and then collect the dust in the bag. Most of valves applied in an automatic control system for driving an operating unit or in a reservoir for introducing the required air into every operating unit are electromagnetic valves.
As we know, the pressure and the temperature in the reservoir will change during the discharged process, and the properties of the fluid substance in the reservoir will also vary all the time. So, it is hard to measure the accurate flow rate of the fluid substance discharged from the reservoir.
In the commonly used flow meter in the industry, such as the orifice meter or the venturi meter, there is a difference in pressure between the upstream and downstream regions of the valve. In other words, these kinds of flow meters are just suitable for the fluid substance in a steady state, and the flow rate of the fluid substance is usually indicated by pressure differences between the upstream and downstream regions of the flow meter.
For convenience, the Instrument Society of American proposed a measurement for determining the flow rate (American National Standard). Referring to
FIG. 1
, a reservoir
11
is connected with a throttle
12
, a thermocouple
13
, and a flow meter
14
in series. Two pressure taps
15
,
16
are provided at the upstream and downstream regions of the valve
17
in the testing area
18
. The method for calculating the flow rate is to determine the difference in pressure at the pressure taps
15
,
16
. This equipment needs a great amount of the fluid substance to maintain a steady state during the discharged process, but it is hard for a factory to set up such a flow meter with a huge volume of the fluid substance. More importantly, the condition of a valve used in the discharged process, e.g. an electromagnetic valve, is usually in a dynamic state, rather than in a steady state (unless the pressure is low). However, it is not reasonable the flow rate of the fluid substance in a steady state is used to represent all the conditions of the fluid substance (including the dynamic state). So, it is tried by the applicant to deal with this problem encountered by the prior art.
SUMMARY OF THE INVENTION
Therefore, a major object of the present invention is to provide a method and an apparatus for determining a flow rate of a fluid substance discharged from a reserving device.
The apparatus according to the present invention includes an instantaneous sensor for measuring an instantaneous state parameter of the fluid substance stored in the reserving device and a data processor electrically connected with the instantaneous sensor for calculating the flow rate of the fluid substance according to the instantaneous state parameter.
In accordance with an aspect of the present invention, the reserving device includes a reservoir for storing the fluid substance, a controlling valve linked to the reservoir for adjusting the flow rate of the fluid substance, and a tube linked to the valve for transporting the fluid substance.
In accordance with another aspect of the present invention, the controlling valve further includes an adjustable valve connected to the reservoir for enabling/disabling the fluid substance to be discharged from the reservoir, and a controller electrically connected to the adjustable valve for controlling the adjustable valve.
In accordance with another aspect of the present invention, the adjustable valve is one selected from a group consisting of a ball valve, an electromagnetic valve, and a diaphragm valve.
In accordance with another aspect of the present invention, the instantaneous sensor is a thermocouple when the state parameter is the temperature of the fluid substance.
In accordance with another aspect of the present invention, the instantaneous sensor is a manometer when the state parameter is the pressure of the fluid substance.
In accordance with another aspect of the present invention, the data processor is a computer.
In accordance with another aspect of the present invention, the flow rate of the fluid substance is determined by an equation
m
.
=
-
ⅆ
m
r
,
t
ⅆ
t
=
-
1
γ
m
r
,
t
=
0
P
r
,
t
[
P
r
,
t
P
r
,
t
=
0
]
1
γ
ⅆ
P
r
,
t
ⅆ
t
where m is the flow rate of the fluid substance, m
r,t
is the mass of the fluid substance in the reserving device, m
r,t=0
is the initial mass of the fluid substance in the reserving device, P
r,t=0
is the initial pressure in the reserving device, P
r,t
is the pressure varying with time in the reserving device, and &ggr; is the specific heat ratio of the fluid substance.
In accordance with another aspect of the present invention, the flow rate of the fluid substance can also be determined by an equation
m
.
=
(
1
-
γ
)
m
r
,
t
=
0
[
T
r
,
t
T
r
,
t
=
0
]
(
2
-
γ
γ
-
1
)
ⅆ
T
r
,
t
ⅆ
t
where m is the flow rate of the fluid substance, m
r,t=0
is the initial mass of the fluid substance in the reserving device, T
r,t=0
is the initial temperature in the reserving device, T
r,t
is the temperature varying with time in the reserving device, and &ggr; is the specific heat ratio of the fluid substance.
In accordance with another aspect of the present invention, a method for determining a flow rate of a fluid substance discharged from a reserving device includes steps of (a) calculating an initial mass m
r,t=0
of the fluid substance in the reserving device, (b) defining a discharged time and then discharging the fluid substance from the reserving device, (c) measuring a pressure P
r,t
in the reserving device, (d) measuring a temperature T
r,t
in the reserving device, and (e) calculating the flow rate {dot over (m)} of the fluid substance.
In accordance with another aspect of the present invention, the step (a) further includes steps of measuring an initial pressure P
r,t=0
in the reserving device, measuring an initial temperature T
r,t=0
in the reserving device, and calculating the initial mass of the fluid substance by an equation PV=mRT.
REFERENCES:
patent: 4108574 (1978-08-01), Bartley et al.
patent: 4109524 (1978-08-01), Smith
patent: 4315523 (1982-02-01), Mahawili et al.
patent: 4633719 (1987-01-01), Vander Heyden
patent: 4669308 (1987-06-01), Jorritsma
patent: 5295083 (1994-03-01), Yano et al.
patent: 5526685 (1996-06-01), Davis
patent: 5966674 (1999-10-01), Crawford et al.
Alston & Bird LLP
Bui Bryan
National Science Council
Shah Kamini
LandOfFree
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