High temperature humidity determining device and process

• US 5,005,410 A
• Filed: 12/20/1989
• Issued: 04/09/1991
• Est. Priority Date: 12/20/1989
• Status: Expired due to Fees

• Current Assignee: Kellogg Company
• Original Assignee: Kellogg Company
• Inventors: Webster, Jeffrey, Richey, Stephen, Tuttup, Robert
• Primary Examiner(s): MYRACLE, JERRY
• Application Number:
  US07/453,915
• Time in Patent Office: 475 Days
• Field of Search: 73/335, 73/336, 73/336.5, 73/338
• US Class Current: 73/335.02
• CPC Class Codes: G01N 25/56 by investigating moisture content
• CPC Class Codes: G01N 33/0016 by regulating a physical variable, e.g. pressure or temperature

Abstract

A high temperature humidity determining device which measures the moisture content of gas streams with temperatures as high as, but not limited to 600° F. The device uses a solid state, thin film polymer type relative humidity/temperature sensor and electronic barometer to measure the properties of the gas stream. The unit does not require laboratory quality oxygen, ice water, distilled water or any other cleaning fluids. In order to avoid damage to the sensor, a sample is cooled to below about 300° F. prior to sampling. This is done by pumping the sample air through a thermostatically controlled sample conduit, and into a positively pressurized and thermostatically controlled sample chamber. A microprocessor calculates the humidity ratio and dew point of the sample or other moist air properties, and delivers data to a visual process indicator, as well as to any other desired output.

Claims

1. A high temperature humidity determining device comprising:

an insulated sample chamber;

means for inducing a heated air sample from a region whose humidity is to be measured to flow into said insulated sample chamber, said inducing means including a sample conduit connected to said region and having at least a cool down portion, whereby the heated air sample is cooled before reaching said insulated sample chamber;

heating means for controlling the temperature of said heated air sample such that said heated air sample always remains above the dew point thereof in said insulated sample chamber and said inducing means;

sensing means for sensing at least the temperature and relative humidity of the air sample in said insulated sample chamber; and

means for determining a humidity parameter of the air sample based upon at least the sensed temperature and relative humidity.

2. The device of claim 1 wherein said inducing means includes a pump connected between said sample conduit and said insulated sample chamber, whereby said insulated sample chamber is positively pressurized by said air sample pumped by said pump.

3. The device of claim 2 wherein said sample conduit includes a flexible portion connected between a rigid cool down portion and said pump.

4. The device of claim 3 wherein said heating means comprises heating elements in said conduit, a conduit temperature sensor and an automatic control device comprising means for controlling actuation of said heating elements based upon the sensed temperature from said conduit temperature sensor. sensor.

5. The device of claim 4 wherein said heating means further comprises heating elements in said heating chamber and a sample chamber temperature sensor, and wherein said automatic control device further comprises means for controlling actuation of said heating elements in said insulated sample chamber based upon the sensed temperature from said sample chamber temperature sensor.

6. The device of claim 5 wherein said automatic control device comprises means having PID control algorithms about a set point for the air sample temperature.

7. The device of claim 2 including an air exhaust in said insulated sample chamber.

8. The device of claim 1 wherein said heating means comprises heating elements in said heating chamber and a sample chamber temperature sensor, and wherein said automatic control device comprises means for controlling actuation of said heating elements in said insulated sample chamber based upon the sensed temperature from said sample chamber temperature sensor.

9. The device of claim 1 wherein said sensing means further comprise means for sensing the absolute air pressure in said insulated sample chamber, and wherein said determining means comprise means for determining the humidity parameter of the air sample based upon the sensed temperature, relative humidity and absolute pressure.

10. The device of claim 9 wherein said humidity parameter is one of the humidity ratio and the dew point temperature of the air sample and wherein said determining means comprise a digital processor programmed to calculate the humidity ratio of the sample air.

11. The device of claim 10 including humidity parameter display means connected to said digital processor for displaying at least one of the calculated humidity ratio and the calculated dew point temperature.

12. The device of claim 1 wherein said insulated sample chamber is formed from Mycalex.

13. The device of claim 1 wherein said relative humidity and temperature sensors are together comprised by a thin film polymer type humidity/temperature sensor.

14. The device of claim 1 including an air tight quick disconnect connector between said sample conduit and said sampling pump.

15. The device of claim 1 including a case containing at least said insulated chamber, said inducing means, said heating means and said determining means, whereby said humidity determining device is portable.

16. A process for determining a humidity parameter of a heated air sample having a temperature greater than 300°

F. and a dew point temperature as high as 210°

F., comprising the steps of;

cooling the air sample to a temperature range above the dew point temperature of the sample and below about 300°

F.;

maintaining the air sample temperature in said range;

continuously flowing the air sample into an insulated sample chamber at positive pressure;

sensing at least the temperature and relative humidity of the air sample maintained in said range by use of a thin film polymer type humidity/temperature sensor; and

calculating the humidity parameter based upon at least the sensed temperature and relative humidity.

17. The process of claim 16 including the steps of sensing the absolute pressure of the air sample and calculating the humidity parameter based upon the sensed temperature, relative humidity and absolute pressure.

18. The process of claim 17 wherein said humidity parameter is one of the humidity ratio and the dew point temperature of the air sample.

19. The process of claim 16 wherein said temperature range is selected such that the sensed relative humidity is greater than 10%.

20. The process of claim 16 including the step of displaying the calculated humidity parameter.

21. The process of claim 16 including the step of continuously flowing the air sample into a sample chamber at a controlled flow rate.

22. The process of claim 16, wherein said heated air sample has a temperature of at least 600°

F.

23. An apparatus for determining a humidity parameter of a heated air sample having a temperature greater than 300°

F., comprising;

means for cooling the air sample to a temperature range above the dew point temperature of the sample and below about 300°

F.;

means for maintaining the air sample temperature in said range;

means for continuously flowing the air sample into an insulated sample chamber at positive pressure;

means for sensing at least the temperature and relative humidity of the air sample maintained in said range by use of a thin film polymer type humidity/temperature sensor; and

means for calculating the humidity parameter based upon at least the sensed temperature and relative humidity.

24. A portable and self-contained, high temperature humidity determining device comprising:

a case;

an insulated sample chamber having an exhaust and being fixed in said case;

a diaphragm type air pump fixed in said case and operatively connected to said sample chamber for pumping air into said sample chamber, whereby a flow of heated sample air in said sample chamber is positively pressurized;

thermostatically controlled heating elements in said sample chamber for maintaining air in said sample chamber at a predetermined temperature;

an airtight sample conduit having one end connected via a quick disconnect to said pump and another end connectable to a region whose humidity is to be measured, whereby heated air from said region is pumped to said sample chamber, said another end of said sample conduit comprising a rigid cool down portion comprising a high heat conductive material, heat trace means, and insulation whereby a temperature of air from said region may drop to near said predetermined temperature, said another end of said sample conduit comprising a flexible portion, said sample conduit being thermostatically heated whereby the air may be maintained at near said predetermined temperature;

thin film polymer type relative humidity and temperature sensors in said sample chamber;

an absolute pressure sensor mounted to said chamber;

a programmable computer fixed in said case and being operatively connected to said sensors, said computer including means for calculating at least the humidity ratio and the dew point of the air in said sample chamber based on signals from said sensors; and

electronic display means in said case and operatively connected to said computer for displaying at least said calculated dew point and humidity ratio.

25. The device of claim 24, wherein said sample chamber is formed of Mycalex.