Two-phase steam measurement system

• US 7,231,835 B2
• Filed: 02/01/2006
• Issued: 06/19/2007
• Est. Priority Date: 05/05/2003
• Status: Expired due to Term

• Current Assignee: Schneider Electric Systems USA, Inc. (Schneider Electric SE)
• Original Assignee: Invensys Systems Incorporated (Invensys PLC)
• Inventors: Mattar, Wade M., Dutton, Robert E.
• Primary Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US11/344,046
• Publication Number:
  US 20060123923A1
• Time in Patent Office: 503 Days
• Field of Search: 738/610.4, 738/610.6
• US Class Current: 73/861.354
• CPC Class Codes: G01F 1/74 Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
• CPC Class Codes: G01F 1/8468 vibrating measuring conduits
• CPC Class Codes: G01F 15/024 involving digital counting
• CPC Class Codes: G01F 15/046 involving digital counting
• CPC Class Codes: G01F 15/08 Air or gas separators in combination with liquid meters; Liquid separators in combination with gas-meters
• CPC Class Codes: G01N 9/002 using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis G01N9/34 takes precedence

Abstract

A steam measurement system includes a Coriolis flowmeter associated with a vibratable flowtube to receive a flow of wet steam. A first sensor is associated with the flowtube to relay information about a motion of the flowtube by way of a first sensor signal. A second sensor determines a property of the flow and relays the property by way of a second sensor signal. A computing device receives the first and second sensor signals and is configured to calculate a steam quality of the flow from the first and second sensor signals. The computing device also may calculate the total heat energy flow rate of the flow. Other implementations may include a full or partial separator to separate the flow of wet steam into a substantially gas flow and a substantially liquid flow and a second Coriolis meter.

Claims

1. A steam measurement system comprising:

a Coriolis flowtube to receive a flow of wet steam, wherein a bulk density of the flow is determined based on a motion of the Coriolis flowtube;

a sensor to determine a property of the flow of wet steam; and

a computing device configured to calculate a steam quality of the flow from the bulk density and the property.

2. The steam measurement system of claim 1 wherein the property is a temperature of the flow and the sensor is a temperature sensor.

3. The steam measurement system of claim 2 wherein the temperature sensor is connected to the outside of the flowtube.

4. The steam measurement system of claim 2 wherein the temperature sensor is inserted into the flow of wet steam.

5. The steam measurement system of claim 1 wherein the property is a pressure of the flow and the sensor is a pressure sensor.

6. The steam measurement system of claim 1 wherein, to calculate the steam quality, the computing device is configured to calculate a density of a vapor phase of the flow from the property and to calculate a density of a liquid phase of the flow from the property.

7. The steam measurement system of claim 6 wherein the computing device includes a memory storing a steam table, the computing device configured to use the steam table to calculate the density of the vapor phase from the property and the density of the liquid phase from the property.

8. The steam measurement system of claim 6 wherein, to calculate the steam quality, the computing device is configured to use the bulk density, the density of the liquid phase, and the density of the gas phase to solve the following equation for the steam quality

9. The steam measurement system of claim 1 wherein the computing device comprises a Coriolis transmitter.

10. The steam measurement system of claim 1 wherein the computing device comprises a flow computer.

11. A method comprising:

passing a flow of wet steam through a vibrating flowtube associated with a Coriolis flowmeter, wherein the Coriolis flowmeter determines the bulk density of the flow of wet steam;

obtaining a temperature or a pressure of the flow of wet steam; and

calculating a steam quality of the flow from the bulk density and the temperature or pressure.

12. The method of claim 11 wherein obtaining a temperature or a pressure of the flow of wet steam comprises obtaining the temperature of the flow of wet steam.

13. The method of claim 12 wherein obtaining the temperature of the flow of wet steam comprises connecting a temperature sensor to the outside of the flowtube.

14. The method of claim 12 wherein obtaining the temperature of the flow of wet steam comprises inserting a temperature sensor into the flow of wet steam.

15. The method of claim 11 wherein obtaining a temperature or a pressure of the flow of wet steam comprises obtaining the pressure of the flow of wet steam.

16. The method of claim 11 wherein calculating the steam quality comprises:

calculating a density of a vapor phase of the flow from the temperature or pressure; and

calculating a density of a liquid phase of the flow from the temperature or pressure.

17. The method of claim 16 wherein calculating the density of the vapor phase of the flow or calculating the density of the liquid phase of the flow from the temperature or pressure comprises:

storing a steam table; and

using the steam table to calculate the density of the vapor phase of the flow or calculate the density of the liquid phase of the flow from the temperature or pressure.

18. The method of claim 16 wherein calculating the steam quality comprises solving the following equation for the steam quality x: