Apparatus and method for transient thermal infrared spectrometry of flowable enclosed materials

• US 5,191,215 A
• Filed: 08/23/1991
• Issued: 03/02/1993
• Est. Priority Date: 01/13/1989
• Status: Expired due to Term

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: McClelland, John F., Jones, Roger W.
• Primary Examiner(s): Hannaher, Constantine
• Application Number:
  US07/749,186
• Time in Patent Office: 557 Days
• Field of Search: 250/343, 250/341, 250/340, 250/339
• US Class Current: 250/341.6
• CPC Class Codes: G01J 5/601 using spectral scanning
• CPC Class Codes: G01N 2021/1714 Photothermal radiometry with measurement of emission
• CPC Class Codes: G01N 2021/1782 In-depth resolution
• CPC Class Codes: G01N 21/71 thermally excited
• CPC Class Codes: G01N 21/85 Investigating moving fluids or granular solids
• CPC Class Codes: G01N 25/72 Investigating presence of flaws

Abstract

A method and apparatus for enabling analysis of a flowable material enclosed in a transport system having an infrared transparent wall portion. A temperature differential is transiently generated between a thin surface layer portion of the material and a lower or deeper portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material, and the altered thermal infrared emission spectrum is detected through the infrared transparent portion of the transport system while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of emitted infrared radiation. The detection is effected prior to the temperature differential propagating into the lower or deeper portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation. By such detection, the detected altered thermal infrared emission spectrum is indicative of characteristics relating to molecular composition of the material.

Claims

1. A method for enabling analysis of a flowable material enclosed in a transport system, comprising the steps of:

transiently generating a temperature differential between a thin surface layer portion of the material and a lower portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material; and

detecting through an infrared transparent portion of the transport system the altered thermal infrared emission spectrum of the material while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of emitted infrared radiation, prior to the temperature differential propagating into the lower portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation, so that the detected altered thermal infrared emission spectrum is indicative of characteristics relating to molecular composition of the material.

2. A method according to claim 1, wherein the step of transiently generating a temperature differential includes applying energy to a surface region of the material adjacent to the infrared transparent portion of the transport system sufficient to cause transient heating in the thin surface layer portion of the material so as to enable transient thermal emission of infrared radiation from the thin surface layer portion.

3. A method according to claim 1, wherein the step of transiently generating a temperature differential includes applying energy to a surface region of the material adjacent to the infrared transparent portion of the transport system sufficient to cause transient cooling of the thin surface layer portion and superposition of the transmission spectrum of the cooled layer on the emission of infrared radiation from the lower portion of the material below the cooled layer and being at a higher temperature than the cooled layer.

4. A method according to claim 1, wherein the step of detecting through the infrared transparent portion of the transport system includes detecting substantially only the transient altered thermal infrared emission spectrum which is substantially free of self-absorption by the material of emission infrared radiation.

5. A method according to claim 1, wherein the step of applying energy to a surface region of the material includes applying one of heat and cold energy, one of pulsingly and continuously to the surface region of the material adjacent to the infrared transparent portion of the transport system.

6. A method according to claim 5, wherein the step of applying energy to the surface region of the material includes one of applying energy directly to the surface region of the material and indirectly through the infrared transparent portion of the transport system, the infrared transparent portion being a thermally transparent portion enabling transmission of the applied energy therethrough.

7. A method according to claim 1, wherein the material is one of a flowing material and a stationary material.

8. A method according to claim 7, wherein the flowable material is one of a liquid, gas, powder, pellets, and a melt.

9. A method according to claim 1, wherein the transport system includes at least one of a container and conduit for the flowable material and having the infrared transparent portion disposed as a window in a wall thereof, the step of detecting including utilizing a detector having a field of view of at least a portion of the window for detecting the transient altered thermal infrared emission spectrum of the material through the window.

10. A method according to claim 9, wherein the step of detecting includes providing a portion of the window facing the flowable material with a convex surface for enabling contact with the flowable material.

11. A method according to claim 9, wherein the material is a flowing material and is positioned in the wall of the transport system so that the moving material moves in parallel to an extent of the window.

12. A method according to claim 9, wherein the material is a moving material and the window is positioned in the wall of the transport system so as to extend transversely to an initial moving direction of the moving material so that the moving material impinges on and is deflected from the window.

13. A method according to claim 1, further comprising the step of determining characteristics relating to the molecular composition of the flowable material in accordance with the detected transient altered thermal emission.

14. An apparatus for enabling analysis of a flowable material enclosed in a transport system, comprising:

an infrared transparent member provided in a wall of the transport system;

means for transiently generating a temperature differential between a thin surface layer portion of the material and a lower portion of the material sufficient to alter the thermal infrared emission spectrum of the material from the black-body thermal infrared emission spectrum of the material; and

means for detecting through the infrared transparent portion of the transport system the altered thermal infrared emission spectrum of the material while the altered thermal infrared emission spectrum is sufficiently free of self-absorption by the material of emitted infrared radiation, prior to the temperature differential propagating into the lower portion of the material to an extent such that the altered thermal infrared emission spectrum is no longer sufficiently free of self-absorption by the material of emitted infrared radiation, so that the detected altered thermal infrared emission spectrum is indicative of characteristics relating to molecular composition of the material.

15. An apparatus according to claim 14, wherein means for transiently generating a temperature differential includes means for applying energy to a surface region of the material adjacent to the infrared transparent portion of the transport system sufficient to cause transient heating in the thin surface layer portion of the material so as to enable transient thermal emission of infrared radiation from the thin surface layer portion.

16. An apparatus according to claim 14, wherein the means for transiently generating a temperature differential includes means for applying energy to a surface region of the material adjacent to the infrared transparent portion of the transport system sufficient to cause transient cooling of the thin surface layer portion and superposition of the transmission spectrum of the cooled layer on the emission of infrared radiation from the lower portion of the material below the cooled layer and being at a higher temperature than the cooled layer.

17. An apparatus according to claim 14, wherein the means for detecting through the infrared transparent portion of the transport system includes means for detecting substantially only the transient altered thermal infrared emission spectrum which is substantially free of self-absorption by the material of emission infrared radiation.

18. An apparatus according to claim 14, wherein the means for applying energy to a surface region of the material includes means for applying one of heat and cold energy, one of pulsingly and continuously to the surface region of the material adjacent to the infrared transparent portion of the transport system.

19. An apparatus according to claim 18, wherein the means for applying energy to the surface region of the material includes one of applying energy directly to the surface region of the material and indirectly through the infrared transparent portion of the transport system, the infrared transparent portion being a thermally transparent portion enabling transmission of the applied energy therethrough.

20. An apparatus according to claim 14, wherein the material is one of a flowing material and a stationary material.

21. An apparatus according to claim 20, wherein the flowable material is one of a liquid, gas, powder, pellets, and a melt.

22. An apparatus according to claim 14, wherein the transport system includes at least one of a container and conduit for the flowable material and having the infrared transparent portion disposed as a window in a wall thereof, the means for detecting including a detector having a field of view of at least a portion of the window for detecting the transient altered thermal infrared emission spectrum of the material through the window.

23. An apparatus according to claim 22, wherein a portion of the window facing the flowable material with a convex surface for enabling contact with the flowable material.

24. An apparatus according to claim 22, wherein the material is a flowing material and is positioned in the wall of the transport system so that the moving material moves in parallel to an extent of the window.

25. An apparatus according to claim 22, wherein the material is a moving material and the window is positioned in the wall of the transport system so as to extend transversely to an initial moving direction of the moving material so that the moving material impinges on and is deflected from the window.

26. An apparatus according to claim 14, further comprising the means for determining characteristics relating to the molecular composition of the flowable material in accordance with the detected transient altered thermal emission.