Carbon nanotube sensing system, carbon nanotube dew point hygrometer, method of use thereof and method of forming a carbon nanotube dew point hygrometer

• US 10,101,219 B2
• Filed: 02/26/2015
• Issued: 10/16/2018
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Cosa Xentaur, The Research Foundation for The State University of New York (State University of New York)
• Original Assignee: Cosa Xentaur, The Research Foundation for The State University of New York (State University of New York)
• Inventors: Samuilov, Vladimir, Ayres, John Lewis
• Primary Examiner(s): Huls, Natalie
• Assistant Examiner(s): Young, Monica S
• Application Number:
  US14/632,540
• Publication Number:
  US 20150233856A1
• Time in Patent Office: 1,328 Days
• Field of Search: 73 2905
• CPC Class Codes: G01K 13/00 Thermometers specially adapted for specific purposes
• CPC Class Codes: G01N 27/121 for determining moisture content, e.g. humidity, of the fluid moisture content of the tested material G01N27/048
• CPC Class Codes: G01N 27/127 comprising nanoparticles

Abstract

A system, a method of use, and a Carbon Nanotube (CNT) condensation sensor for determining a dew point and/or ice point is provided. For example, a sensing system may include a thermal device configured to generate heating or cooling to change a temperature of a surface, a temperature sensor for measuring the temperature of the surface, a controller configured to control the thermal device, a carbon nanotube (CNT) condensation sensor mounted on the surface having a moisture sensitive resistance and a processor configured to determine one or more parameters based on the moisture sensitive resistance of the CNT condensation sensor and the temperature measured by the temperature sensor. The one or more parameter can be used to determine the dew point and/or ice point. A method for forming a carbon nanotube (CNT) condensation sensor is also provided.

Claims

1. A system comprising:

a carbon nanotube (CNT) condensation sensor having a moisture sensitive resistance, where a current is supplied to the CNT condensation sensor from a current source and where a voltage across the CNT condensation sensor is detected;

a thermal device configured to generate heating or cooling to change a temperature of the CNT condensation sensor;

a temperature sensor for measuring a temperature of the CNT condensation sensor;

a controller configured to control the thermal device; and

a processor configured to determine one or more parameters based on the moisture sensitive resistance determined from the supplied current and the detected voltage of the CNT condensation sensor and the temperature measured by the temperature sensor, the temperature measured being a result of the controlled heating or cooling generated by the thermal device.

2. The system of claim 1, wherein the controller is configured to control a temperature scan rate of the thermal device.

3. The system of claim 2, wherein the temperature scan rate is between about 0.001°

C./sec and about 10°

C./sec.

4. The system of claim 2, wherein the temperature scan rate includes a fast temperature scan rate of between about 0.1 and about 10°

C./sec.

5. The system of claim 4, wherein the temperature scan rate includes a slow temperature scan rate of between about 0.001 and about 0.1°

C./sec.

6. The system of claim 5, wherein the controller is configured to switch between the fast temperature scan rate and the temperature slow scan rate.

7. The system of claim 1, wherein the thermal device is a multi-stage thermoelectric device.

8. The system of claim 1, further comprising a current source coupled to the temperature sensor and to the CNT condensation sensor;

and voltage detector configured to detect voltage across the temperature sensor and the CNT condensation sensor, the detected voltages being proportional to a resistance of the temperature sensor and the moisture sensitive resistance of the CNT condensation sensor.

9. The system of claim 1, wherein the processor is configured to determine the one or more parameters based on analyzing the moisture sensitive resistance over time.

10. The system of claim 9, wherein the one or more parameters being selected from a group consisting of maximum resistance point with respect to temperature, a first derivative of resistance with respect to temperature and a second derivative of resistance with respect to temperature.

11. The system of claim 10, wherein the processor is configured to determine a dew point based on at least one of the one or more parameters.

12. The system of claim 11, wherein when the dew point is greater than 0(°

C.), a T_inflection (°

C.) is the dew point, where T_inflection is a temperature where;

     1) the first derivative is a minimum,

     2) the first derivative is less than 0 for both T>

T_inflection and T<

T_inflection,

     3) the second derivative equals 0 and

     4) the second derivative is greater than 0 for surface temperatures T_surface (°

C.) above L_inflection (°

C.) and the second derivative is less than 0 for surface temperatures T_surface (°

C.) below T_inflection (°

C.).

13. The system of claim 11, wherein when the dew point is less than 0(°

C.), the dew point is determined based on a frost point, T_frost, when no T_inflection is detected, where T_frost=T_ice, where T_ice a temperature where;

     1) the first derivative is less than 0 for T_surface (°

C.)>

T_ice (°

C.),

     2) the first derivative is greater than 0 for T (°

C.)<

T_ice (°

C.),

     3) the first derivative is equal to 0 at T_ice (°

C.) or T) or the first derivative is undefined at T_ice (°

C.),

     4) conditions 1-3 resulting in a maximum extremum or “

peak”

in the R_cnt (ohms) versus T_surface (°

C.) curve where T_surface (°

C.) equals T_ice (°

C.), and

     5) immediately following T_ice (°

C.), as the surface temperature is further decreased, a magnitude of the moisture sensitive resistance R_CNT drops off abruptly in magnitude providing a characteristic icing signature.

14. A method comprising:

controlling a temperature of a carbon nanotube (CNT) condensation sensor, the temperature is controlled to start at a maximum temperature, the maximum temperature being higher than an expected dew point, the controlling the temperature including decreasing the temperature at a controllable scan rate;

supplying a current to the CNT condensation sensor from a current source;

detecting, continuously a voltage across the CNT condensation sensor over time;

detecting, continuously a voltage across a temperature sensor over time, the temperature sensor disposed near the CNT condensation sensor;

calculating moisture sensitive resistance of the CNT condensation sensor from the continuously detected voltage across the CNT condensation sensor and the supplied current; and

determining one or more parameters based on the moisture sensitive resistance and the temperature.

15. The method of claim 14, wherein the one or more parameters being selected from a group consisting of maximum resistance point with respect to temperature, a first derivative of resistance with respect to temperature and a second derivative of resistance with respect to temperature.

16. The method of claim 15, further comprising:

determining an ice point temperature T_ice based the one or more parameters.

17. The method of claim 16, wherein the decrease in the temperature of the surface is stopped at the T_ice.

18. The method of claim 17, wherein the controlling of the temperature of a surface, further including increasing the temperature of the surface to the maximum temperature when the T_ice is reached.

19. The method of claim 16, wherein the T_ice is where:

1) the first derivative is less than 0 for T_surface (°

C.)>

T_ice (°

C.),

     2) the first derivative is greater than 0 for T (°

C.)<

T_ice (°

C.),

     3) the first derivative is equal to 0 at T_ice (°

C.) or the first derivative is undefined at T_ice (°

C.),

     4) conditions 1-3 resulting in a maximum extremum or “

peak”

in the R_cnt (ohms) versus T_surface (°

C.) curve where T_surface (°

C.) equals T_ice (°

C.), and

     5) immediately following T_ice (°

C.), as the surface temperature is further decreased, a magnitude of the moisture sensitive resistance R_CNT drops off abruptly in magnitude providing a characteristic icing signature.

20. The method of claim 16, further comprising:

detecting an inflection point temperature T_inflection based the one or more parameters.

21. The method of claim 20, wherein T_inflection is a temperature where:

1) the first derivative is a minimum,

     2) the first derivative is less than 0 for both T>

T_inflection, inflection and T<

T_inflection,

     3) the second derivative equals 0 and

     4) the second derivative is greater than 0 for surface temperatures T_surface (°

C.) above T_inflection (°

C.) and the second derivative is less than 0 for surface temperatures T_surface (°

C.) below T_inflection (°

C.).

22. The method of claim 21, further comprising:

determining a dew point temperature T_dew.

23. The method of claim 22, wherein when T_inflection is greater than 0, T_dew=T_inflection.

24. The method of claim 22, wherein when T_inflection is less than 0, T_dew is determined based on a frost point T_frost.

25. The method of claim 21, wherein the method detects the T_dew of polar molecules in a gas mixture.

26. The method of claim 25, wherein the gas mixture includes components selected from a group consisting of oxygen (O₂), nitrogen (N₂), hydrogen (H₂), carbon dioxide (CO₂), and hydrocarbon molecules such as methane (CH₄), ethane (C₂H₆), propane (C₃H₈), and butane (C₄H₁₀).

27. The method of claim 25, wherein the polar molecules are selected from a group consisting of water and ammonia.

28. The method of claim 21, wherein the method detects the T_dew of a target polar molecule in a background gas stream consisting of nonpolar molecules and polar molecules in which the dew point of the background polar molecules is lower than the dew point of the target polar molecule.