Thermal transient anemometer

• US 4,848,147 A
• Filed: 07/10/1987
• Issued: 07/18/1989
• Est. Priority Date: 07/10/1987
• Status: Expired due to Fees

• Current Assignee: James L. Bailey, Josip Vresk
• Original Assignee: James L. Bailey, Josip Vresk
• Inventors: Bailey, James L., Vresk, Josip
• Primary Examiner(s): Goldsten, Herbert
• Application Number:
  US07/072,104
• Time in Patent Office: 739 Days
• Field of Search: 73/204, 73/204.17, 73/204.24
• US Class Current: 73/204.17
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/6888 Thermoelectric elements, e.g. thermocouples, thermopiles
• CPC Class Codes: G01F 1/6986 with pulsed heating, e.g. dynamic methods
• CPC Class Codes: G01P 5/10 by measuring thermal variables

Abstract

A thermal transient anemometer having a thermocouple probe which is utilized to measure the change in temperature over a period of time to provide a measure of fluid flow velocity. The thermocouple probe is located in the fluid flow path and pulsed to heat or cool the probe. The cooling of the heated probe or the heating of the cooled probe from the fluid flow over a period of time is measured to determine the fluid flow velocity. The probe is desired to be locally heated near the tip to increase the efficiency of devices incorporating the probe.

Claims

1. A method of measuring fluid flow velocity, comprising:

providing a thermocouple probe means for measuring the temperature of a fluid in a fluid flow path;

inserting said probe means into said fluid flow path and measuring the temperature of said fluid;

applying at least one power pulse to said probe means to provide arbitrary initial probe conditions and arbitrary temperature differential between said probe means and said fluid;

delaying for a predetermined period after said power pulse to allow the initial probe conditions to become negligible and measuring the temperature of said probe means a first time,

measuring the temperature of said probe means at a second time, following said first time;

an

correlating said temperature measurements of the fluid and probe to provide a measure of the fluid flow velocity.

2. The method as defined in claim 1 including providing said temperature differential by heating said probe means.

3. The method as defined in claim 2 including heating said probe means by electrical resistance heating.

4. The method as defined in claim 2 including providing said probe means with a thermocouple junction adjacent a free end or tip of said probe means and only heating a local area of said probe means adjacent said tip.

5. The method as defined in claim 1 including providing said temperature differential by cooling said probe means.

6. The method as defined in claim 5 including cooling said probe means by Peltier cooling.

7. The method as defined in claim 5 including providing said probe means with a thermocouple junction adjacent a free end or tip of said probe means and only cooling a local area of said probe means adjacent said tip.

8. The method as defined in claim 1 including correlating said temperature measurements includes calculating at least one parameter related to the coefficient of thermal exchange and the temperature of said fluid.

9. The method as defined in claim 1 wherein said applied power pulse is formed of an arbitrary magnitude and arbitrary time period.

10. The method as defined in claim 1 including forming said probe means as a sheath type thermocouple probe having a grounded probe tip, a pair of different electrical resistance calibration wires, forming a Seebeck junction adjacent said tip from said pair of wires and connected to said tip by a high electrical resistance wire.

11. The method as defined in claim 1 including forming said probe means as a sheath type thermocouple probe having a probe tip, a pair of calibration wires, a first of said wires grounded to said tip and a second of said wires having a low electrical resistance connected adjacent said tip to a high electrical resistance wire portion forming a Seebeck junction and said wire portion connected to said tip.

12. The method as defined in claim 1 including forming said probe means as a sheath type thermocouple probe having a grounded probe tip formed of high electrical resistance material and a pair of low electrical resistance calibration wires connected to said tip.

13. The method as define in claim 1 including forming said probe means as an ungrounded sheath type thermocouple probe having a tip and a pair of low electrical resistance calibration wires connected adjacent said tip by a third wire of a high electrical resistance.

14. The method as defined in claim 1 including forming said probe means as a grounded sheath type thermocouple probe having a tip formed of high electrical resistance material, a pair of calibration wires and a third wire of low electrical resistance all grounded to said tip.

15. The method as defined in claim 1 including forming said probe means as a grounded sheath type thermocouple probe having a tip, a pair of calibration wires grounded to said tip and a third wire of low electrical resistance connected adjacent said tip by a wire portion of high electrical resistance to form a Seebeck junction and said wire portion connected to said tip.

16. An apparatus for measuring fluid flow velocity, comprising:

thermocouple probe means for measuring the temperature of a fluid in a fluid flow path when said probe means is inserted into said fluid flow path;

means for applying at least one power pulse to said probe means to provide arbitrary probe conditions and an arbitrary temperature differential between said probe means and said fluid;

means for delaying for a predetermined period of time after said power pulse to allow the initial probe conditions to become negligible and, for measuring the temperature of said probe means a first time, and at a second time following said first time; and

means for correlating said temperature measurements of the fluid and the probe to provide a measure of the fluid flow velocity.

17. The apparatus as define in claim 16 including means for heating said probe means to provide said temperature differential.

18. The apparatus as defined in claim 17 wherein said heating means include means for heating said probe means by electrical resistance heating.

19. The apparatus as defined in claim 17 wherein said probe means include a thermocouple junction adjacent a free end or tip of said probe means and said means for heating include means for only heating a local area of said probe means adjacent said tip.

20. The apparatus as defined in claim 16 including means for cooling said probe means to provide said temperature differential.

21. The apparatus as defined in claim 20 wherein said cooling means include means for cooling said probe means by Peltier cooling.

22. The apparatus as defined in claim 20 wherein said probe means include a thermocouple junction adjacent a free end or tip of said probe means and said means for cooling include means for only cooling a local area of said probe means adjacent said tip.

23. The apparatus as defined in claim 16 wherein said correlating means include means for calculating at least one parameter related to the coefficient of thermal exchange and the temperature of said fluid.

24. The apparatus as defined in claim 16 wherein said applied power pulse is formed of arbitrary magnitude and arbitrary time period.

25. The apparatus as defined in claim 16 including said probe means formed as a sheath type thermocouple probe having a grounded probe tip, a pair of different electrical resistance calibration wires, a Seebeck junction formed adjacent said tip from said pair of wires an connected to said tip by a high electrical resistance wire.

26. The apparatus as defined in claim 16 including said probe means formed as a sheath type thermocouple probe having a probe tip, a pair of calibration wires, a first of said wires grounded to said tip and a second of said wires having a low electrical resistance connected adjacent said tip to a high electrical resistance wire portion to form a Seebeck junction and said wire portion connected to said tip.

27. The apparatus as defined in claim 16 including said probe means formed as a sheath type thermocouple probe having a grounded probe tip formed of high electrical resistance material and a pair of low electrical resistance calibration wires connected to said tip.

28. The apparatus as defined in claim 16 including said prob means formed as an ungrounded sheath type thermocouple probe having a tip and a pair of low electrical resistance calibration wires connected adjacent said tip by a third wire of a high electrical resistance.

29. The apparatus as define in claim 16 including said probe means formed as a grounded sheath type thermocouple probe having a tip formed of high electrical resistance material, a pair of calibration wires and a third wire of low electrical resistance all grounded to said tip.

30. The apparatus as defined in claim 16 including said probe means formed as a grounded sheath type thermocouple probe having a tip, a pair of calibration wires grounded to said tip and a third wire of low electrical resistance connected adjacent said tip by a wire portion of high electrical resistance to form a Seebeck junction and said wire portion connected to said tip.