DESC:FIELD
The present disclosure relates to the field of steam generating systems and more specifically to an apparatus for controlling steamparameters.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Generally, the steam generation systems employ an apparatus having pressure reducing valves to reduce the pressure of the steam generated in order to attain a pre-desired pressure. In addition to reducing the output pressure of the steam, it is also essential to meter the flow rate of the steam through the steam generation system. To measure the flow rate of the steam, flow metering devices are positioned at the steam side. However, the functioning of the conventional flow metering devices is limited due to the high temperature, compressibility and density of the steam, and variation in the load and operating conditions.
Additionally, since the pressure reducing valve and the steam metering device along with the other components of the apparatus are positioned at different locations in a steam generation system, the construction of the system becomes bulky and complex. Further, use of additional components leads to an increase in the manufacturing and maintenance cost of the system.
There, is therefore, felt a need for an apparatus for controlling pressure, temperature and flow rate of steam.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide an apparatus for sensing pressure and temperature of steam
Another object of the present disclosure is to provide an apparatus that reduces the pressure of the steam to a pre-desired value.
Another object of the present disclosure is to provide an apparatus to control the temperature of outlet steam so as to maintain the external application temperature to a pre-desired value.
Another object of the present disclosure is to provide an apparatus to maintain level of process fluid in an application at a desired value.
Yet another object of the present disclosure is to provide an apparatus that accurately measures and controls flow rate of steam.
Another object of the present disclosure is to measure dryness fraction of steam entering control valve.
Still another object of the present disclosure is to provide an apparatus that singlehandedly performs the functions of a control valve and a flow meter, thus being cost-effective.
Another object of the present disclosure is to provide an apparatus that is simple in construction.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure discloses an apparatus for sensing pressure and temperature of steamflowing through a conduit for controlling the flow rate of the steam through the control valve. The apparatus comprises:
• a control valve positioned along the conduit 300 carrying thesteam
• a first pressure sensing unit positioned upstream of the control valve and a second pressure sensing unit positioned downstream of the control valve;
• a temperature sensing unit positioned downstream of the control valve; and
• a central processing unit comprising:
• an analyzing unit configured to receive sensed signals from the first pressure sensing unit, the second pressure sensing unit, the temperature sensing unit and the control valve;
• a computing unit to process information analyzed by the analyzing unit based on a programmable logic contained therein;
• a position sensing and controlling unit (125) configured to receive signals from the control valve (105) and the computing unit (135), the position sensing and controlling unit (125) configured to transmit signals to the control valve (105) to measure and compute steamparameters of flow rate and dryness fraction, and vary at least one dimension of an opening in the control valve (105) to vary flow through said control valve (105).
The central processing unit includes a display unit coupled to the computing unit to facilitate visualization of information.
The central processing unit includes a data transmission unit configured to transmit signals to a remote receiver and the data transmission unit coupled to the display unit.
In various embodiments, the central processing unit includes an external sensing unit configured to sense condition of an external process fluid in the form of pressure, temperature or fluid level.
The analyzing unit includes a memory and a controller with the memory configured to store a set value of a process parameter.
In an embodiment, the control valve is a proportional control valve configured to meter the quantity of thesteamaccording to a predetermined set of parameters.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
An apparatus for sensing pressure and temperature of asteam, of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 shows a schematic of the apparatus, in accordance with a first embodiment of the present disclosure;
Figure 2 shows a schematic of the apparatus, in accordance with a second embodiment of the present disclosure;
Figure 3 shows a schematic of a control valve of the apparatus, of Figure 1 and 2, in a closed position;
Figure 4 shows a schematic of the control valve of the apparatus, of Figure 1 and 2, in a partially closed position;
Figure 5 illustrates a schematic view of the control valve of the apparatus, of Figure 1 and 2, in a fully open position; and
Figure 6 shows a front view of the apparatus.
LIST OF REFERENCE NUMERALS USED IN DETAILED DESCRIPTION AND DRAWING
100, 200 – apparatus
105, 205 –control valve
105a, 205a – seat
105b, 105b – plug
110, 210 – first pressure sensing unit
115, 215 – second pressure sensing unit
120 – analyzing unit
125 – position sensing and controlling unit
130, 230 – temperature sensing unit
135, 235 – computing unit
140, 240 – display unit
145, 245 – data transmission unit
150 – external signal sensor
220 – third pressure sensing unit
225 –mechanical controller
300- conduit
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof.
A preferred embodiment of an apparatus for controlling pressure or temperature or flow rate of steam, of the present disclosure will now be described in detail with reference to Figures 1-6.
The apparatus for controlling pressure or temperature or flow rate of steam100 (hereinafter referred to as the apparatus “100”) is configured to reduce the input pressure of the steam passing there through to a desired value and calculate the flow rate of the steam based on parameters such as input pressure and output pressure of the steam, percentage required for the passage of steam.
In accordance with a first embodiment, as illustrated in Figure 1, the apparatus 100 includes a control valve 105 positioned along a conduit (300), a plurality of sensing units 110,115,130 and a central processing unit 200. The plurality of sensing units 110,115,130 are positioned at a location that is upstream or downstream of the control valve 105. At least a first pressure sensing unit 110 is positioned upstream of the control valve 105, and at least a second pressure sensing unit 115 is positioned downstream of the control valve 105. A central processing unit 200 is mounted on the control valve 105 and configured to receive signals from the plurality of sensing units (110,115,130). The central processing unit 200 processes the received signals from the plurality of sensing units (110,115,130) and devises a response based on a programmable logic. The central processing unit 200 further includes an analyzing unit 120, a position sensing and controlling unit 125, a temperature sensing unit 130, a computing unit 135, 235, a display unit 140,240, data transmission unit 145 and an external sensing unit 150.
The control valve 105 is defined by a seat 105A and a plug 105B. The plug 105B is configured to be displaced upwardly from the seat 105A. In an embodiment, the control valve 105 is a pressure reducing valve.
Steam enters the control valve 105 at a pressure P1, which is sensed by the first pressure sensing unit 110. Based on the sensed pressure P1, the first pressure sensing unit 110 generates a first sensed signal which is received by the computing unit 135. The pressure P2 of the steam flowing out of the control valve 105 is sensed by the second pressure sensing unit 115. Based on the sensed pressure P2, the second pressure sensing unit 115 generates a second sensed signal which is received by the analyzing unit 120 and the computing unit 135.
The analyzing unit 120 includes a memory (not specifically shown in figures) and a controller (not specifically shown in figures). The memory is configured to store a pre-desired value of the pressure P2 as a set value. The controller is configured to cooperate with the memory to receive the set value of the pressure P2. The controller is further configured to receive the second sensed signal, and compare it with the set value of the pressure P2 to compute a pressure differential. Based on the pressure differential, the controller generates a command signal.
The position sensing and controlling unit 125 is configured to receive the command signal. The position sensing and controlling unit 125 is further configured to control the actuation of the control valve 105 based on the command signal.
More specifically, if the pressure P2 is less than the set value of pressure P2, the position sensing and controlling unit 125 will generate a control signal to open the control valve 105. The area of opening herein expressed as percentage of opening depends on the amount of pressure that needs to be reduced for attaining the set value of pressure P2. On the other hand, if the pressure P2 is more than the set value of pressure P2, the position sensing and controlling unit 125 will cause the control valve 105 to close. This loop continues till the pressure P2 sensed by the second pressure sensing unit 115 becomes equivalent to the set value of pressure P2. The position sensing and controlling unit 125 is further configured to transmit a third sensed signal based on the percentage opening of the control valve 105.
The percentage opening of the control valve 105 based on the pressure P2 at the outlet of the control valve 105 is illustrated in Figure 3 through Figure 5. When the apparatus is not in operation, the control valve 105 remains fully closed, because of which the percentage opening of the control valve 105 is 0% (as seen in Figure 3). When the pressure P2 is less than the set value pressure P2, the plug 105B is upwardly displaced by the position sensing and controlling unit 125 to open the control valve 105, either partially (when pressure P2 is slightly less than the set value of pressure P2) as illustrated in Figure 4 or fully (when pressure P2 is less than the set value of pressure P2) as illustrated in Figure 5. Upward displacement of the plug 105B facilitates the formation of an annular portion to let out the steam, thereby increasing the pressure of the steam. The annular portion varies with respect to the upward displacement of the plug 105B. Since, the configuration of the seat 105A and the plug 105B is already known, the area of the opening of the control valve 105 i.e., the area of the annular portion can be calculated with the help of empirical formulae.
The temperature sensing unit 130 is configured to sense the temperature of the steam after it is released from the control valve 105 i.e. downstream of the control valve 105. The temperature sensing unit 130 is further configured to generate a fourth sensed signal which is received by the computing unit 135.
Based on the first sensed signal, the second signal, the third sensed signal and the fourth signal, the computing unit 135 is configured to compute the flow rate of the steam passing through the control valve 105.
In an embodiment, the pressure P1, the pressure P2, the percentage opening of the control valve 105, the temperature and the computed value of the flow rate of the steam is displayed by a display unit 140 coupled to the computing unit 135. In another embodiment, the display unit 140 is coupled with a data transmission unit 145 configured to transmit the pressure P1, the pressure P2, the percentage opening of the control valve 105, the temperature and the computed value of the flow rate of the steam to a remote device selected from the group of cloud, laptop, a mobile device, a desktop, a personal digital assistant, a palmtop, a tablet and the like, having communication capabilities.
In an embodiment, the controller is a PID controller.
In accordance with a second embodiment, as illustrated in Figure 2, the apparatus 200 includes a control valve 205 connected with a first pressure sensing unit 210, a second pressure sensing unit 215, a third pressure sensing unit 220, a mechanical controller 225, a temperature sensing unit 230, and computing unit 235.
The control valve 205 is defined by a seat 205A, a plug 205B and an actuator (not specifically shown in figures). The plug 205B is configured to be displaced upwardly from the seat 205A. In an embodiment, the control valve 205 is a pressure reducing valve.
Steam enters the control valve 205 at a pressure P1 which is sensed by the first pressure sensing unit 210. Based on the sensed pressure P1, the first pressure sensing unit 210 generates a first sensed signal. The pressure P2 of the steam flowing out of the control valve 205 is sensed by the second pressure sensing unit 215. Based on the sensed pressure P2, the second pressure sensing unit 215 generates a second sensed signal. The pressure P2 of the steam is also sent as a feedback to the mechanical controller 225 which is coupled to the third pressure sensing unit 220. The mechanical controller 225 is configured to exert pressure P3 on the actuator of the control valve 205. The third pressure sensing unit 220 is configured to generate a third sensed signal based on the pressure P3.
The temperature sensing unit 230 is configured to sense the temperature of the steam after it is released from the control valve 205. The temperature sensing unit 230 is further configured to generate a fourth sensed signal which is received by the computing unit 235.
The first sensed signal, the second sensed signal, the third sensed signal and the fourth sensed signal are received by the computing unit 235. Based on the third sensed signal corresponding to pressure P3, the percentage opening of the control valve 205, is calculated by the computing unit 235. Coupling the value of percentage opening with the first sensed signal, the second signal, and the fourth signal, the computing unit 235 computes the flow rate of the steam passing through the control valve 205.
In an embodiment, the pressure P1, the pressure P2, the percentage opening of the control valve 205, the temperature and the computed value of the flow rate of the steam is displayed by a display unit 240 coupled to the computing unit 235. In another embodiment, the display unit 240 is coupled with a data transmission unit 245 configured to transmit the pressure P1, the pressure P2, the percentage opening of the control valve 205, the temperature and the computed value of the flow rate of the steam to a remote device selected from the group of cloud, laptop, a mobile device, a desktop, a personal digital assistant, a palmtop, a tablet and the like, having communication capabilities.
The computing units 135, 235 include a processor which is configured to execute a command signal based on a set of rules to calculate the flow rate of the steam. The pressures P1 and P2 are measured on absolute scale. The logic corresponding to the rules are as follows:
(a) Logic 1
This method obtains Pcritical from a range that varies from (0.5*P1) to (0.6* P1) for calculating the flow rate of the steam.
a) Case 1: P2>Pcritical, wherein flow rate is directly proportional to (P1-P2) and percentage opening of control valve 105, 205;
• P1 and P2 are sensed by pressure sensing units 110, 115, 210, 215 to generate a first sensed signal and a second sensed signal; and
• Percentage opening of the control valve 105, 205 is calculated from the diameter of the plug 105B, 205B and the seat 105A, 205A of the control valve 105, 205, and the upward displacement of the plug 105B, 205B from the seat 105A, 205A;
b) Case 2: P2<=Pcritical, wherein flow rate is directly proportional to P1 and area of opening of control valve 105, 205
• P1 is sensed by pressure sensing units 110, 210 to generate a first sensed signal; and
• Percentage opening of the control valve 105, 205 is calculated from the diameter of the plug 105B, 205B and the seat 105A, 205A of the control valve 105, 205, and the upward displacement of the plug 105B, 205B from the seat 105A, 205A.
(b) Logic 2
• Kv is defined as the flow rate in cubic meters per hour [m3/h] of water at a temperature of 16º Celsius with a pressure drop of 1 bar across control valve 105, 205;
• The control valve 105 is calibrated on a test rig by passing water at 16º Celsius and adjusting the flow such that pressure drop across unit is 1 bar. The flow rate is measured by an already calibrated flow meter. Thus Kv of the control valve 105 in a fully open condition is calculated;
• The Kv value with respect to the different positions of the opening of the control valve 105is calculated by same method as described above;
• The values of Kv at different positions of the opening of the control valve 105 and the density of steam at various pressures are fed in computing unit135;
• The opening of the control valve 105 is measured by position sensing and controlling unit125;
• The pressure values P1 and P2 are sensed by the pressure sensing units 110, 115to generate a first sensed signal and a second sensed signal; and
• From the first sensed signal and the second sensed signal, percentage opening of the control valve 105, Kv and the density of steam, the flow rate is determined.
(c) Logic 3
This method is applicable only for the second embodiment, wherein the mechanical controller 225 is employed.
• The pressure P3 inside mechanical controller 225 is sensed by the third pressure sensing unit 220;
• By measuring P3, the upward displacement of the plug 205B from seat 205A is computed, and used for computing the percentage opening of control valve 205.
• The flow rate is thereafter determined as described in Logic 1 and Logic 2.
The above methods are used to accurately compute low flow rates as well as high flow rates of the steam.
The present disclosure envisages a process for pressure reduction and steam metering.
In an embodiment, the external sensing unit 150 is a temperature sensor which facilitates controlling of the temperature of the steam downstream of the control valve 105,205 as required by the application. The external sensing unit 150 is configured to sense temperature of an external process and generates a fifth sensed signal fed to the analyzing unit 120.The analyzing unit 120 is configured to store a preset value of temperature as defined by a user. This preset value of the temperature is stored in the memory of the analyzer unit 120. The analyzing unit 120 compares the temperature sensed by the external sensing unit 150 with the preset value and a differential temperature value is computed. A command signal is then generated in response to this temperature differential. The position sensing and controlling unit 125 receives this command signal and is configured to control actuation of the control valve 105.Based on the first sensed signal, the second signal, the third sensed signal and the fourth signal, the computing unit 135 is configured to compute the flow rate of the steam passing through the control valve 105.
In another embodiment, the external sensing unit 150 is a process fluid level sensor which facilitates controlling of the process fluid leveling application. The external sensing unit 150 is configured to sense process fluid level of an external process and generate a fifth sensed signal fed to the analyzing unit 120. The analyzing unit 120 is configured to store a preset value of level as defined by a user. This preset value of the level is stored in the memory of the analyzer unit 120. The analyzing unit 120 compares the process fluid level sensed by the external sensing unit 150 with the preset value and a differential fluid level value is computed. A command signal is then generated in response to this process fluid level differential. The position sensing and controlling unit 125 receives this command signal and is configured to control actuation of the control valve 105. Based on the first sensed signal, the second signal, the third sensed signal and the fourth signal, the computing unit 135 is configured to compute the flow rate of the steam passing through the control valve 105.
In yet another embodiment, the apparatus 100 is configured to measure the dryness fraction of steam entering the control valve 105.The computing unit 135,235 calculates the saturation temperature at condition P2.Based on the comparison between the sensed temperature T2 is greater than the calculated saturation temperature of P2 then apparatus 100 can measure dryness fraction.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
Logic 4: Measurement of dryness fraction of steam
The dryness fraction of steam ‘x1’ entering the control valve is to be determined when the steam exiting the control valve is superheated. The first pressure sensor ‘P1’ measures the pressure of steam entering the control valve. From ‘P1’, the specific enthalpy of steam entering the control valve ‘h1’ is
h1 = hf1 + x1 * (hg1 – hf1)
where hf1 = enthalpy of saturated liquid at pressure ‘P1’ &
hg1 = enthalpy of saturated steam at pressure ‘P1’
Both hf1 and hg1 values can be determined once the pressure ‘P1’ is known.
The second pressure sensor P2 and temperature sensor T2 measures the pressure and temperature of steam exiting the control valve respectively.
If T2 > Tsat2, then enthalpy of steam ‘h2’ existing the control valve is
h2 = hg2 + Cp * (T2 – Tsat2)
where hg2 = enthalpy of saturate steam at pressure ‘P2’
Tsat2 = saturated steam temperature at pressure ‘P2’ *
Cp = specific heat of steam at pressure ‘P2’
Cp, Tsat2 and hg2 can be determined once the pressure ‘P2’ is known
The expansion of steam through control valve is isenthalpic and hence h1 and h2 will be equal
h1 = h2
hf1 + x1 * (hg1 – hf1 ) = hg2 + Cp * (T2 – Tsat2)
P1, P2 and T2 are measured and hf1, hg1, hg2, Cp and Tsat2 are determined from P1 and P2. From this, the only unknown parameter dryness fraction ‘x1’ can be determined.
TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an apparatus for sensing pressure and temperature of a steamthat:
• efficiently reduces pressure of the steam to a desired value;
• accurately meters the flow of the steam;
• that is simple in construction; and
• is cost-effective.
The foregoing description of the specific embodiments so fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, step, or group of elements, steps, but not the exclusion of any other element, step, or group of elements, or steps.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM:
1. An apparatus (100) for sensing pressure and temperature of steam flowing through a conduit (300) and thereby controlling the flow rate there through, said apparatus (100) comprising:
• a control valve (105) positioned along said conduit(300) carrying said steam;
• at least a first pressure sensing unit (110) positioned upstream of said control valve (105) and at least a second pressure sensing unit (115) positioned downstream of said control valve (105);
• a temperature sensing unit (130) positioned downstream of said control valve (105);
• a central processing unit (200) comprising:
o an analyzing unit (120) configured to receive sensed signals from said first pressure sensing unit (110), said second pressure sensing unit (115), said temperature sensing unit (130);
o a computing unit (135) to process information analyzed by said analyzing unit (120) based on a programmable logic contained therein configured to receive signals from said analyzing unit (120) to compute steam parameters of flow rate based on parameters sensed by said first pressure sensing unit (110), said second pressure sensing unit (115)and percentage opening of the control valve (105) and to compute dryness fraction based on parameters sensed by said first pressure sensing unit (110), said second pressure sensing unit (115) and said temperature sensing unit (130);
o a position sensing and controlling unit (125)configured to receive sensed signals from said first pressure sensing unit (110), said second pressure sensing unit (115), said temperature sensing unit (130)to control the actuation of the control valve 105.
2. The apparatus (100) as claimed in claim 1, wherein said central processing unit (200) includes a display unit (140,240) coupled to said computing unit (135) to facilitate visualization of information.
3. The apparatus (100) as claimed in claim 1, wherein said central processing unit (200) includes a data transmission unit (145) configured to transmit signals to a remote receiver; said data transmission unit (145) coupled to said display unit (140,240).
4. The apparatus (100) as claimed in claim 1, wherein said central processing unit (200) includes an external sensing unit (150) configured to sense condition of an external process fluid.
5. The apparatus (100) as claimed in claim 4, wherein said external sensing unit (150) is configured to sense pressure of an external process fluid.
6. The apparatus (100) as claimed in claim 4, wherein said external sensing unit (150) is configured to sense temperature of an external process fluid.
7. The apparatus (100) as claimed in claim 4, wherein said external sensing unit (150) is configured to sense level of an external process fluid.
8. The apparatus (100) as claimed in claim 1, wherein said analyzing unit (120) includes a memory and a controller (not shown in any figures), said memory configured to store a set value of a process parameter.
9. The apparatus (100) as claimed in claim 1, wherein said control valve (105) is a proportional control valve, said control valve (105) configured to vary the flow of steam according to a predetermined set of pressure or temperature parameters.
10. The apparatus (100) as claimed in claim 1, wherein said control valve (105) is a proportional control valve, said control valve (105) configured to vary the flow of steam according to a predetermined set of pressure or temperature parameters.