TEMPERATURE DIFFERENTIAL FLUID SENSOR

Abstract

A fluid detecting device for detecting the presence of a substance in a fluid in an area comprising: a heating element arranged in said area, a first thermal sensor arranged adjacent to said heating element adapted to detect a temperature (T1) at said heating element, wherein said heating element is coated with a hydrophobic sorbent adapted to adsorb a substance present in said fluid in said area. The invention further relates to a method for detecting the presence of a substance in a fluid in an area.

Claims

1. A fluid detecting device for detecting the presence of a substance in a fluid in an area comprising: a heating element arranged in said area, and a first thermal sensor arranged adjacent to said heating element (4) adapted to detect a temperature (T1) at said heating element, wherein said heating element is coated with a hydrophobic sorbent adapted to adsorb a substance present in said fluid in said area.

2. The fluid detecting device according to claim 1, further comprising: a second thermal sensor adapted to detect a second temperature (T2) at said heating element, said second thermal sensor being arranged adjacent to and on an opposite side of said thermal element in relation to said first thermal sensor.

3. The fluid detecting device according to claim 2, further comprising: a second heating element arranged in said area at a predetermined distance from said heating element, and a third thermal sensor arranged adjacent to said second heating element, said third thermal sensor adapted to detect a third temperature (T3) at said second heating element.

4. The fluid detecting device according to claim 3, further comprising: a fourth thermal sensor adapted to detect a fourth temperature (T4) at said second heating element, said fourth thermal sensor being arranged adjacent to and on an opposite side of said second heating element in relation to said third thermal sensor.

5. The fluid detecting device according to claim 2, wherein said area is a section of a flow channel, said first thermal sensor being arranged upstream of said thermal element, and said second thermal sensor being arranged downstream of said thermal element.

6. The fluid detecting device according to claim 4, wherein said area is a section of a flow channel, said third thermal sensor being arranged upstream of said second heating element, and said fourth thermal sensor being arranged downstream of said second heating element.

7. The fluid detecting device according to claim 1, wherein said hydrophobic sorbent is carbon or a molecular sieve with pores.

8. The fluid detecting device according to claim 1, wherein said sorbent is a nanostructure based on carbon having hydrophobic properties.

9. The fluid detecting device according to claim 1, wherein said substance is a hydrocarbon.

10. The fluid detecting device according to claim 1, wherein said substance is benzene.

11. The fluid detecting device according to claim 1, wherein said sorbent is gold.

12. The fluid detecting device according to claim 1, wherein said substance is mercury.

13. A method for detecting the presence of a substance in a fluid in an area, comprising: measuring a temperature of said fluid at a first point of time (T1-1) by means of a thermal sensor arranged in said area, providing heat by means of a heating element arranged adjacent to said thermal sensor, said heating element being coated with a hydrophobic sorbent adapted to adsorb a substance present in said fluid, measuring said temperature of said fluid at a second point of time (T1-2) by means of said thermal sensor, and determining the potential presence of said substance based on the temperature difference in temperature between said first point of time (T1-1) and said second point of time (T1-2), and a known input of power provided to said heating element.

14. The method for detecting the presence of a substance according to claim 13, wherein said step of providing heat comprises raising the temperature of said heating element to the vaporization temperature of said substance.

15. Use of the fluid detecting device according to claim 1, for detecting a potential leak of a substance into a gas mask.

16. Use of the fluid detecting device according to claim 1, for detecting a substance in a gas outlet or inlet to a facility intended for breathing humans or animals.

17. Use of the fluid detecting device according to claim 1, for detecting a substance in a liquid, said device further comprising evacuation means to, at least temporary, evacuate said liquid from said area to operate said fluid detecting device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above objects, as well as additional objects, features and advantages of the present invention, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, when taken in conjunction with the accompanying drawings, wherein:

[0028] FIG. 1a is a schematic view of a simple fluid detecting device according to the invention having only one thermal sensor.

[0029] FIG. 1b is a schematic view of a simple fluid detecting device according to the invention having two thermal sensors.

[0030] FIG. 2 is a schematic view of a fluid detecting device according to the invention intended to be placed in a gas flow.

[0031] FIG. 3 is a schematic view of a fluid detecting device according to the invention intended to be placed in a gas flow having a second thermal sensor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0032] FIG. 1a is a schematic view of a simple fluid detecting device 1 according to the invention having a heating element 4 that is coated with a hydrophobic sorbent 3. A thermal sensor 5 is placed adjacent the heating element. The simple fluid detecting device may be placed on a wall of a room to detect a gaseous substance that is adsorbed by the hydrophobic sorbent. The substance may by e.g. benzene (or another hydrocarbon) if the hydrophobic sorbent is a carbon based nano-structure or mercury is the hydrophobic sorbent is made of gold.

[0033] The hydrophobic sorbent coating 3 is adapted to adsorb a substance. At intervals the heating element is actuated and the temperature T1 of the heating element 4 and thus also the temperature of the hydrophobic sorbent 7 is raised. The air surrounding the heating element is naturally also raised via heat conduction from the hydrophobic sorbent. If a substance is adsorbed and present in the hydrophobic sorbent, the substance will absorb some of the heat from the heating element and the temperature measured by the thermal element will be slightly lower. If the temperature of the heating element is raised above the evaporation temperature of the adsorbed substance, the substance will be evaporated, a process requiring a lot of energy, thus leaving less energy for heating the air surrounding the heating element. The temperature elevation measured by the thermal sensor will thus be lower if the substance is present in the hydrophobic sorbent. The temperature elevation at the thermal sensor will thus be dependent on how much heat is adsorbed by the substance and will thereby be dependent of the amount of the substance present in the hydrophobic sorbent. Detection of the substance may thus be achieved. The sensor may further be connected to a warning device, as e.g. a light or a buzzer, to warn people in the area around the sensor that the substance is present. If the substance is benzene, it is hazardous to people and they should thus leave the area or room where the sensor is located.

[0034] FIG. 1b shows a schematic view of the simple fluid detecting device 1 shown in FIG. 1a with a second thermal sensor 6, where the second thermal sensor is placed further away from the heating element than the first heating element 5. The second thermal sensor 6 will measure the ambient temperature while the first thermal sensor 5 will measure a temperature that is affected by the heating element 4. With this configuration it is possible to measure continuously to probe for a substance. If the temperature decreases at the first thermal sensor 5 but not at the second thermal sensor 6 some amount of the substance has been adsorbed and evaporated from the hydrophobic sorbent 7.

[0035] FIG. 2 shows a second configuration of the fluid detecting device 1 of FIG. 1b placed on a wall where the second thermal sensor 6 instead is placed at the same distance from the heating element 4 as first thermal sensor 5 but on the other side of the heating element 4. As heated air from the heating element normally will move upwards, the second thermal sensor 6 will measure the ambient temperature, while the first thermal sensor 5 will measure the temperature that is affected by the heating element 4 and by any substance adsorbed by the hydrophobic sorbent 7.

[0036] FIG. 3 shows a fluid detecting device 1 placed on the wall 3 of a flow channel 2 in which air is flowing in the direction of the arrow 8. If a substance that is possible to be adsorbed by the hydrophobic sorbent is present in the air the substance will be adsorbed. A first thermal sensor 5 measures the temperature downstream of a heating element. The heating element 4 may at intervals be actuated to raise the temperature of the heating element 4 and the hydrophobic sorbent 7. If substance is present in the hydrophobic sorbent 7, energy will be absorbed by the substance and the temperature T1 measured at the first thermal sensor 5 will be lower than if the substance is not present in the hydrophobic sorbent 7. If the temperature is raised so that the temperature at the hydrophobic sorbent 7 is above the evaporation temperature of the substance, substantially more energy will be required and the temperature at the first thermal sensor will be even lower compared to if no substance is present at the hydrophobic sorbent 7. The second thermal sensor 6, placed upstream the heating element 4, measures the ambient temperature T2 in the gas flow in the flow channel 2 that may be used for determining difference between T1 and T2 and compare it to a calibration. In that way an estimation of the concentration of the substance present in the gas flow 8 may be made.

[0037] FIG. 4 shows a fluid detecting device 1 placed on the wall 3 of a flow channel 2 in which air is flowing in the direction of the arrow 8 as the one in FIG. 3 but further comprising a third thermal sensor 9, a second heating element 8, and a fourth thermal sensor 10. The three additional components 8, 9, 10, together form a mass flow meter able to measure the mass flow of the gas flowing through the flow channel 2. When the gas flow is known, the concentration of any substance present in the gas may be calculated from the temperature T1 measured at the first thermal sensor 5 of the fluid detecting device, where the temperature T1 will be affected by the heating element in proportion to the amount of substance adsorbed to the hydrophobic sorbent, if any.

[0038] It is understood that other variations in the present invention are contemplated and in some instances, some features of the invention can be employed without a corresponding use of other features. E.g., as also described above, the fluid detecting device could be used in liquids by placing the fluid detecting device in an area where the liquid could be temporary removed when the heating element is operated for detecting adsorbed substance in the sorbent coating. Accordingly, it is appropriate that the appended claims be construed broadly in a manner consistent with the scope of the invention.