Flowmeter fluid composition and temperature correction

• US 5,237,523 A
• Filed: 07/25/1990
• Issued: 08/17/1993
• Est. Priority Date: 07/25/1990
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Bonne, Ulrich, Kubisiak, David
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US07/558,034
• Time in Patent Office: 1,119 Days
• Field of Search: 364/571.01-571.05, 364/571.07, 364/510, 364/556, 364/564, 364/863, 73/861.01-861.03, 73/204.18, 73/204.19, 374/1, 374/29, 374/40, 374/43, 374/44
• US Class Current: 702/100
• CPC Class Codes: G01F 1/68 by using thermal effects
• CPC Class Codes: G01F 1/696 Circuits therefor, e.g. constant-current flow meters
• CPC Class Codes: G01F 1/6965 comprising means to store calibration data for flow signal calculation or correction
• CPC Class Codes: G01F 15/04 of gases to be measured
• CPC Class Codes: G01F 25/15 specially adapted for gas meters G01F25/11 - G01F25/14, G01F25/17 take precedence

Abstract

A method for correcting the flow measurement of a gaseous or liquid fluid of interest for changes in the composition and temperature of that fluid in a flowmeter of the hot element type is disclosed in which an uncorrected flow value signal for the fluid of interest in relation to a hot element sensor output is corrected by applying a first correction factor to the output based on certain unique physical parameters of the fluid of interest which nominally include thermal conductivity, k, specific heat, c_p, and temperature, T, obtaining an uncorrected flow measurement value from the corrected output and obtaining the corrected flow measurement by applying a second correction factor to the uncorrected flow measurement value based on the certain unique physical parameters.

Claims

1. A method of obtaining a signal indicative of fluid flow rate (V_C) which is corrected for variations in specific heat (C_pe), thermal conductivity (K_e) and temperature (T_e) utilizing an output (G) of a first dynamic microbridge exposed to the fluid, comprising the step of:

(A) measuring C_pe, K_e and T_e using the G output of said first dynamic microbridge;

(B) calculating a gauge correction value (C_G) as a first function of C_pe, K_e and T_e ;

(C) calculating a flow correction value (C_V) as a second function of C_pe, K_e and T_e ;

(D) producing a corrected gauge output (G_C) as a function of G and C_G ;

(E) calculating an uncorrected flow value (V) as a function of G_C ; and

(F) producing a corrected fluid flow output signal (V_C) as a function of (V) and C_V.

2. The method of claim 1 wherein the gauge correction factor is determined according to a relationship selected from:

##EQU3## and the volumetric correction factor (C_V) is determined according to a relationship selected from;

##EQU4## Where;

n₁ through n₆, A_i, B_i, m_i, C_i,

D_i, q_i and r_i =constants determined by the calibration process, and

k_co, c_pco and T_c =thermal conductivity, specific heat and temperature of the calibration gas.

3. The method of claim 1 wherein c_pe, k_e and T_e are determined by a second microbridge in relatively static communication with said fluid of interest.

4. The method of claim 2 wherein c_pe, k_e and T_e are determined by a second microbridge in relatively static communication with said fluid of interest.

5. The method of claim 2 wherein the gauge correction factor is determined according to the relationship:

space="preserve" listing-type="equation">C.sub.G =(k/.sub.e /k.sub.co).sup.n1 (c.sub.pe /c.sub.pco).sup.n2 (T.sub.e /T.sub.c).sup.n3

and the volumetric correction factor C_V is determined according to the relationship;

space="preserve" listing-type="equation">C.sub.V =(k/.sub.e /k.sub.co).sup.n4 (c.sub.pe /c.sub.pco).sup.n5 (T.sub.e /T.sub.c).sup.n6

and n₁ through n₆, respectively, are approximately equal to;

-0.015331

-0.060124

7. The method of claim 3 Wherein the gauge correction factor is determined according to the relationship:

space="preserve" listing-type="equation">C.sub.G =(k/.sub.e /k.sub.co).sup.n1 (c.sub.pe /c.sub.pco).sup.n2 (T.sub.e /T.sub.c).sup.n3

and the volumetric correction factor C_V, is determined according to the relationship;

space="preserve" listing-type="equation">C.sub.V =(k/.sub.e /k.sub.co).sup.n4 (c.sub.pe /c.sub.pco).sup.n5 (T.sub.e /T.sub.c).sup.n6

and n₁ through n₆, respectively, are approximately equal to;

-0.015331

-0.060124

0.387617

-0.85033

0.9845898

0.027236

8. The method of claim 2 wherein said C_G determined in step (C) is determined according to a known relationship among variables selected from the group consisting of specific heat (c_pe), the differential of specific heat with respect to temperature (dc_pe /dT), thermal conductivity (k_e), the differential of thermal conductivity with respect to temperature (dK_e /dT), density, viscosity, speed of sound, optical absorption or diffusibility.

9. The method of claim 2 wherein said step (C) of determining C_G is omitted and C_G is set equal to unity.

11. The method of claim 9 wherein the gauge correction factor is determined according to a relationship selected from:

##EQU5## and the mass correction factor (C_M) is determined according to a relationship selected from;

##EQU6## Where;

n₁ through n₆, A_i, B_i, m_i, C_i, D_i, q_i and r_i =constants determined by the calibration process, and

k_co, c_pco and T_c =thermal conductivity, specific heat and temperature of the calibration gas.

12. The method of claim 9 wherein c_pe, k_e and T_e are determined by a second microbridge in relatively static communication with said fluid of interest.

6. 387617

-0.85033

0.9845898

0.027236

10. A method of obtaining a signal indicative of the mass fluid flow rate (M_C) which is corrected for variations in specific heat (C_pe), thermal conductivity (K_e) and temperature (T_e) utilizing an output (G) of a first dynamic microbridge exposed to the fluid, comprising the steps of:

(A) measuring C_pe, K_e and T_e using said G output of said first dynamic microbridge;

(B) calculating a gauge correction value (C_G) as a first function of C_pe, K_e and T_e ;

(C) calculating a mass flow correction value (C_M) as a second function of C_pe, K_e and T_e ;

(D) producing a corrected gauge output (G_C) as a function of G and C_G ;

(E) calculating an uncorrected mass flow value (M) as a function of G_C ;

(F) producing a corrected mass flow output signal (M_C) as a function of (M) and C_M.

13. The method of claim 10 wherein c_pe, k_e and T_e are determined by a second microbridge in relatively static communication with said fluid of interest.

14. The method of claim 10 wherein said C_G determined in step (C) is determined according to a known relationship among variables selected from the group consisting of specific heat (c_pe), the differential of specific heat with respect to temperature (dc_pe /dT), thermal conductivity (k_e), the differential of thermal conductivity with respect to temperature (dk_e /dT), density, viscosity, speed of sound, optical absorption or diffusibility.

15. The method of claim 10 wherein said step (C) of determining C_G is omitted and C_G is set equal to unity.

17. The method of claim 15 wherein the gauge correction factor is determined according to a relationship selected from:

##EQU7## and the energy correction factor (C_E) is determined according to a relationship selected from;

##EQU8## Where;

n₁ through n₆, A_i, B_i, m_i, C_i, D_i, q_i and r_i =constants determined by the calibration process, and

k_co, c_pco and T_c =thermal conductivity, specific heat and temperature of the calibration gas.

18. The method of claim 15 wherein c_pe, k_e and T_e are determined by a second microbridge in relatively static communication with said fluid of interest.

16. A method of obtaining a signal indicative of the mass fluid flow rate (E_C) which is corrected for variations in specific heat (C_pe), thermal conductivity (K_e) and temperature (T_e) utilizing and output (G) of a first dynamic microbridge exposed to the fluid, comprising the steps of:

(A) measuring C_pe, K_e and T_e using the G output of said first dynamic microbridge;

(B) calculating a gauge correction value (C_G) as a first function of C_pe, K_e and T_e ;

(C) calculating a energy flow correction value (C_E) as a second function of C_pe, K_e and T_e ;

(D) producing a corrected gauge output (G_C) as a function of G and C_G ;

(E) calculating an uncorrected energy flow value (E) as a function of G_C ; and

(F) producing a corrected energy flow output signal (E_C) as a function of (E) and C_E.

19. The method of claim 16 wherein c_pe, k_e and T_e are determined by a second microbridge in relatively static communication with said fluid of interest.

20. The method of claim 16 wherein said C_G determined in step (C) is determined according to a known relationship among variables selected from the group consisting of specific heat (c_pe), the differential of specific heat with respect to temperature (dc_pe /dT), thermal conductivity (k_e), the differential of thermal conductivity with respect to temperature (dk_e /dT), density, viscosity, speed of sound, optical absorption or diffusibility.

21. The method of claim 16 wherein said step (C) of determining C_G is omitted and C_G is set equal to unity.