Flowmeter fluid composition correction

• US 4,961,348 A
• Filed: 12/16/1988
• Issued: 10/09/1990
• Est. Priority Date: 12/16/1988
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Bonne, Ulrich
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US07/285,897
• Time in Patent Office: 662 Days
• Field of Search: 73/204.18, 73/204.25, 73/204.26, 73/204.27, 73/204.19, 73/861.02, 364/510
• US Class Current: 73/861.02
• CPC Class Codes: G01F 1/68 by using thermal effects
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/6965 comprising means to store calibration data for flow signal calculation or correction
• CPC Class Codes: G01F 1/86 Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
• CPC Class Codes: G01F 15/043 using electrical means

Abstract

A method for correcting the flow measurement of a gaseous fluid of interest for changes in the composition of that fluid in a flowmeter of the microanemometer class is disclosed in which an uncorrected flow value signal for the fluid of interest in relation to a microanemometer sensor output is corrected by applying a correction factor to the flow value signal based on certain unique physical parameters of the fluid of interest which nominally include thermal conductivity, k, specific heat, c_p, and density, q.

Claims

1. A method for compensating the flow measurement of a gaseous fluid of interest for changes in the composition of that fluid in a flowmeter of the microbridge class having a first dynamic microbridge exposed to the flow and producing a flow-related output signal, comprising the steps of:

obtaining an on-going, uncorrected nulled microbridge sensor output (S_o) for the fluid of interest;

obtaining an on-going, uncorrected nulled mass flow value (M_o) or volumetric flow value (V_o) for the fluid of interest in relation to the microbridge sensor output;

obtaining the specific heat (c_p) thermal conductivity (k) and density (q); and

applying a correction factor normalized with reference to a particular gas to the flowrate signal to obtain the corrected mass flow value (M_o *) or volumetric flow (V_o *) and sensor output S_o * according to a relationship selected from;

space="preserve" listing-type="equation">M.sub.o */M.sub.o =(k/k.sub.o).sup.X.sbsp.1 (c.sub.p c.sub.po).sup.X.sbsp.2

7. The method of claim 1 wherein the relationship is selected from:

space="preserve" listing-type="equation">M.sub.o */M.sub.o =(k/k.sub.o).sup.X.sbsp.1 (c.sub.p c.sub.po ).sup.X.sbsp.2 (q/q.sub.o).sup.X.sbsp.3

or

space="preserve" listing-type="equation">V.sub.o */V.sub.o =(k/k.sub.o).sup.z.sbsp.1 (c.sub.p c.sub.po ).sup.z.sbsp.2 (q/q.sub.o).sup.z.sbsp.3

and

S_o */S_o =1.

9. The method of claim 1 wherein k and c_p are determined by a second microbridge means in relatively static communication with the fluid of interest.

10. The method of claim 1 wherein the correction factors are normalized with respect to CH₄.

11. The method of claim 1 wherein the steps of obtaining correction factors are applied to a plurality of gases.

13. The method of claim 7 wherein the correction factors are normalized with respect to CH₄.

15. The method of claim 9 further comprising monitoring the density (g) of the fluid of interest.

16. The method of claim 9 wherein k and c_p are determined by a second microbridge means in relatively static communication with the fluid of interest.

17. The method of claim 10 wherein k and c_p are determined by a second microbridge in relatively static communication with the fluid of interest.

18. The method of claim 9 wherein the steps of obtaining correction factors are applied to a plurality of gasses.

22. The method of claim 13 wherein the relationship is selected from:

space="preserve" listing-type="equation">M.sub.o */M.sub.o =(k/k.sub.o).sup.X.sbsp.1 (c.sub.p c.sub.po ).sup.X.sbsp.2

or

space="preserve" listing-type="equation">V.sub.o */V.sub.o =(k/k.sub.o).sup.z.sbsp.1 (c.sub.p c.sub.po ).sup.z.sbsp.2

and

space="preserve" listing-type="equation">S.sub.o */S.sub.o =1 .

23. The method of claim 17 wherein k and c_p are determined by a second microbridge means in relatively static communication with the fluid of interest.

24. The method of claim 16 wherein the correction factors are normalized with respect to CH₄.

25. The method of claim 16 wherein the steps of obtaining correction factors are applied to a plurality of gases.

2. or

View Dependent Claims (8)

8. The method of claim 2 wherein k and c_p are determined by a second microbridge means in relatively static communication with the fluid of interest.

3. or

View Dependent Claims (19)

19. The method of claim 3 wherein said plurality of gases include CH₄, CO₂, O₂ air, C₃ H₈, Ar and He.

4. or

5. and

6. or

View Dependent Claims (12)

12. The method of claim 6 wherein said plurality of gases include CH₄, CO₂, O₂ air, C₃ H₈, Ar and He.

14. A method for compensating the flow measurement of gaseous fluid of interest for changes in the composition of that fluid in a flowmeter having a first dynamic microbridge exposed to the flow and producing a flow-related output signal, comprising the steps of:

obtaining an on-going, uncorrected, nulled dynamic microbridge sensor output for the fluid of interest;

obtaining an on-going, uncorrected nulled mass flow value or volumetric flow value for the fluid of interest in relation to the dynamic microbridge sensor output;

obtaining the specific heat (c_p) and thermal conductivity (k) of the fluid of interest; and

applying an on-going, time-variable correction factor to the flow value normalized with respect to a particular reference gas to obtain the corrected mass flow value or volumetric flow valve and sensor output according to a known relationship, among values of specific heat (c_p) and thermal conductivity (k) normalized with respect to the reference gas.

20. The method of claim 14 wherein the correction factors are normalized with respect to CH₄.

26. The method of claim 20 wherein said plurality of gases include CH₄, CO₂, O₂ air, C₃ H₈, Ar and He.

21. A method for compensating the flow measurement of a gaseous fluid of interest for changes in the composition of that fluid in a flowmeter having a first dynamic microbridge exposed to the flow and producing a flow-related output signal, comprising the steps of:

obtaining an on-going, uncorrected nulled microbridge sensor output (S_o) for the fluid of interest;

obtaining an on-going, uncorrected nulled mass flow value (M_o) or volumetric flow value (V_o) for the fluid of interest in relation to the microbridge sensor output;

obtaining the specific heat (c_p) and thermal conductivity (k); and

applying a correction factor normalized with respect to a particular reference gas to the flowrate valve to obtain the corrected mass flow value (M_o *) or volumetric flow (V_o *) and sensor output S_o * according to a relationship selected from;

space="preserve" listing-type="equation">M.sub.o */M.sub.o =(k/k.sub.o).sup.x.sbsp.1.(c.sub.p /c.sub.po).sup.x.sbsp.2

space="preserve" listing-type="equation">V.sub.o */V.sub.o =(k/K.sub.o).sup.z.sbsp.1.(c.sub.p /c.sub.po).sup.z.sbsp.2

and

space="preserve" listing-type="equation">S.sub.o */S.sub.o =1

space="preserve" listing-type="equation">S.sub.o */S o=(k/k.sub.o).sup.y.sbsp.1.(c.sub.p /c.sub.po).sup.y.sbsp.2

Where;

M*=corrected mass flow

S*=corrected output (sensor)

V*=corrected volumetric flow

k/ko=normalized thermal conductivity

c_p /c_po =normalized specific heat

o=refers to the base or reference gas

x₁, x₂, or y₁, y₂ or z₁, and z₂ =are exponents.

27. The method of claim 21 wherein the correction factors are normalized with respect to CH.