Determination of fluid parameters

Patent metadata

Field	Value
Publication number	US-11226300-B2
Application number	US-201515555433-A
Country	US
Kind code	B2
Filing date	Mar 5, 2015
Priority date	Mar 5, 2015
Publication date	Jan 18, 2022
Grant date	Jan 18, 2022

Abstract

A method for determining fluid parameters, such as a heat capacity cPρ, a calorific value Hp, a methane number MN, and/or a Wobbe index WI, of an unknown fluid (g). An unknown flow (55) of the fluid (g) is set in a sensor device (10), the sensor device (10) comprising a thermal flow sensor (1) and a pressure sensor device (15) for measuring at least one temperature value T1, T2, a further parameter, and differential pressure value Δρ over a flow restrictor (14). Using these measurement parameters T1, T2, Δρ and calibration data, the calorific value Hp, and/or the Wobbe index WI, or parameters indicative thereof, of an unknown fluid (g) are calculated. The invention also relates to such a sensor device (10) and to a computer program product for carrying out such a method.

First claim

The invention claimed is:

1. A method for determining a characteristic parameter of a fluid, said fluid flowing in a fluid flow through a sensor device, the sensor device comprising:
a thermal flow sensor device with a heater element and at least one temperature sensor,
a flow restrictor arranged between first and second positions in said fluid flow, and
a pressure sensor device for determining a pressure difference in the fluid between said first and second positions,
the method comprising:
(i) establishing the fluid flow with an unknown value through said sensor device with at least part of the fluid overflowing said thermal flow sensor;
(ii) activating the heating element of said thermal flow sensor and measuring at least one first temperature with said at least one temperature sensor and at least one second temperature;
(iii) measuring first and second absolute pressures in the fluid at the first and second positions, respectively, or
measuring a differential pressure in the fluid between the first and second positions with said pressure sensor device; and
(iv) determining from the measured first and second temperatures and calibration data a heat conductivity of said fluid of the fluid;
(v) determining from the measured first and second temperatures, the measured pressure value(s) and calibration data a microscopic force of the fluid;
(vi) determining from said heat conductivity and microscopic force said characteristic parameter of the fluid with correlation functions, the characteristic parameter being selected from the group consisting of the heat capacity, the calorific value and a parameter indicative thereof, the methane number, and the Wobbe index and a parameter indicative thereof.

2. The method according to claim 1 , wherein the thermal flow sensor device comprises first and second temperature sensors for determining the first and second temperatures, wherein the heater element is arranged between said first and second temperature sensors.

3. The method according to claim 2 , wherein the microscopic force is determined by rescaling at least part of the relevant calibration data prior to interpolation or wherein the measurement of the fluid is performed at several fluid flow values and the determined fluid parameter averaged.

4. The method according to claim 1 , wherein the calibration data comprises first calibration data and second calibration data, the first and second calibration data comprising first and second temperatures and the pressure value(s) for at least one calibration fluid, wherein the first and second calibration data is stored in at least one lookup table, and wherein said heat conductivity and said microscopic force are determined by interpolation of the respective calibration data.

5. The method according to claim 4 , wherein the first calibration data comprise the heat conductivity of the at least one calibration fluid and the second calibration data comprise the microscopic force of the at least one calibration fluid.

6. The method according to claim 1 , wherein the correlation functions are based on a quadratic Ansatz.

7. The method according to claim 1 , further comprising:
(vii) determining a volume flow of the fluid flow of the fluid from the heat capacity and the heat conductivity determined previously.

8. The method according to claim 7 , further comprising:
(viii) determining an energy transfer per time unit from the volume flow and the calorific value of the fluid.

9. The method according to claim 1 , further comprising:
(ix) outputting the heat capacity, the calorific value, the Wobbe index, the methane number, an energy transfer determined from the volume fluid and the calorific value of the fluid, or a parameter indicative of any one thereof.

10. The method according to claim 1 , wherein the fluid or the at least one calibration fluid is a burnable gas or a mixture thereof, or a natural gas or a mixture thereof.

11. The method according to claim 1 , wherein first calibration data and second calibration data comprise first and second temperatures and the pressure value(s) for at two calibration fluids, wherein the first and second calibration data is stored in at least one lookup table, and wherein said heat conductivity and said microscopic force are determined by interpolation of the respective calibration data.

12. A sensor device for measuring a characteristic parameter selected from the group consisting of a heat capacity, a calorific value, a methane number, and a Wobbe index of a fluid, or a parameter indicative of any one thereof, the sensor device comprising:
a flow channel for the fluid, the flow channel having an inlet and an outlet for the fluid,
a thermal flow sensor device with a heater element and two temperature sensors and the heater element arranged therebetween,
a flow restrictor arranged between first and second positions in said flow channel,
at least one pressure sensor device for determining a pressure difference in the fluid between said first and second positions,
and a digital control circuit comprising a memory,
wherein the digital control circuit is configured to carry out a method comprising:
(i) establishing the fluid flow with an unknown value through said sensor device with at least part of the fluid overflowing said thermal flow sensor;
(ii) activating the heating element of said thermal flow sensor and measuring at least one first temperature with said at least one temperature sensor and at least one second temperature;
(iii) measuring first and second absolute pressures in the fluid at the first and second positions, respectively, or measuring a differential pressure in the fluid between the first and second positions with said pressure sensor device; and
(iv) determining from the measured first and second temperatures and calibration data a heat conductivity of said fluid of the fluid;
(v) determining from the measured first and second temperatures, the measured pressure value(s) and calibration data a microscopic force of the fluid;
(vi) determining from said heat conductivity and microscopic force said characteristic parameter of the fluid with correlation functions, the characteristic parameter being selected from the group consisting of the heat capacity, the calorific value and a parameter indicative thereof, the methane number, and the Wobbe index and a parameter indicative thereof.

13. The sensor device according to claim 12 , wherein a memory is configured to store first and second calibration data, and wherein the digital control circuit is configured to retrieve the first and second calibration data from said memory and to determine the characteristic parameter.

14. The sensor device according to the claim 12 , wherein the thermal flow sensor device is a CMOS flow sensor device.

15. The sensor device according to claim 13 , wherein the correlations functions are stored in said memory.

16. The sensor device according to claim 13 , wherein the digital control circuit is configured to determine the heat capacity, the calorific value or the parameter indicative thereof, the methane number or the parameter indicative thereof, or a Wobbe index or the parameter indicative thereof, of the fluid with said correlation functions.

17. A non-transitory computer usable memory medium having a computer readable program code embodied therein for execution by a digital control circuit of a sensor device, said sensor device comprising:
a flow channel for the fluid, the flow channel having an inlet and an outlet for the fluid,
a thermal flow sensor device with a heater element a

Assignees

• Sensirion Ag

Inventors

• Hornung Mark
• Rüegg Andreas

Classifications

• G01N33/225

  Gaseous fuels, e.g. natural gas · CPC title

• G01N25/005 Primary

  by investigating specific heat · CPC title

• G01N25/20 Primary

  by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity (calorimeters per se G01K) · CPC title