Measuring and testing – Instrument proving or calibrating – Gas or liquid analyzer
Patent
1996-08-15
1998-07-07
Noland, Thomas P.
Measuring and testing
Instrument proving or calibrating
Gas or liquid analyzer
73 105, 73 407, 210640, G01M 320, G01F 2500
Patent
active
057772037
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION AND PRIOR ART
My invention is related to a method and a device for emission of small amounts of tracer gas to the surroundings in a controlled manner. The application primarily intended is in the so called passive tracer gas technique for ventilation measurements. However, there are other applications--for instance for production of calibration gases for analysing instruments, for studying flow patterns in chemical reactors or for studying spreading of contaminations.
Description of the Problem with Passive Tracer Gas Sources
A passive tracer gas source is a container emitting small amounts of gas to the air at a constant rate. In ventilation measurement, such tracer gas sources are placed in the premises together with samplers for the air. Analysis of the sampler then gives a value with respect to the concentration of tracer gas in the air. The ventilation in the premises can be calculated based upon the concentration. The technique itself is well established and has been used for thousands of ventilation measurements.
In a new variant of the technique, which I have proposed and developed, it is required that the rate of emission of tracer gas can be controlled and adapted to the size of rooms in the building, where the ventilation is to be determined. If this technique can be put into practice, it will involve a major improvement of the ventilation measurement technique. The new technique is called homogeneous emission technique and is internationally published by me.
Until about two years ago tracer gas sources for ventilation measurements were based on storage of the tracer substance in a container in a flowing form, said container being closed by means of a membrane which is permeable to the gas form tracer substance. It was also that type which I used at the beginning The greatest problem with this type of "permeation source" is that the rate of emission cannot be changed and the emission cannot be stopped. Another problem is that it takes X very long time (several weeks) before the rate of emission has been stabilized for a newly produced source. Therefore, I produced tracer gas sources based upon a different technique--capillary diffusion--a technique which I now exclusively use. Capillary diffusion sources are also a well-known technique. They are used for making gas mixtures having a known concentration for calibration of various analysing equipment for example. The rate of emission of the capillary source may be controlled by selecting the dimensions of the capillary in a suitable way. This type of source stabilizes the rate of emission momentarily. By closing off the capillary, one can also inhibit the emission.
However, it turned out that also the capillary source involves problems. One of the problems is that air in the container is expanded on temperature increase, whereby the air, which is saturated with tracer gas, is pressed out through the capillary and increases the rate of emission in an incontrollable manner if the source is subjected to temperature variations. Another problem is that the gas may condensate In the narrow capillary, which involves a drastic change of the rate of emission. The letter problem becomes particularly dramatic if one tries to control the rate of emission by changing the dimension of the capillary by pushing down a metal wire in it. Therefore, I have not been able to use the capillary sources as variable sources as I intended in the beginning.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and a device for emitting small amounts of gas from a substance in condensated form to the surroundings with controllable rate.
The invention which solved of the above mentioned problem involves placement of a membrane, which is permeable to the tracer gas but not to air, between the container having the tracer substance and the capillary. Thus, the capillary is not in direct communication with the space containing the tracer substance. The risk for temperature expansion as well as capillary condensation is elimi
REFERENCES:
patent: 3209579 (1965-10-01), Roberts
patent: 3516278 (1970-06-01), Klien et al.
patent: 3824836 (1974-07-01), Lyshkow
patent: 3854894 (1974-12-01), Kloss et al.
patent: 3968675 (1976-07-01), Briggs
patent: 4016743 (1977-04-01), Henderson et al.
patent: 4018077 (1977-04-01), Leach
patent: 4063446 (1977-12-01), Fuhrmann
patent: 4172378 (1979-10-01), Limp
patent: 4419882 (1983-12-01), Ishii et al.
patent: 4445364 (1984-05-01), Stieff et al.
patent: 4493207 (1985-01-01), Dempsey
patent: 4769122 (1988-09-01), Morrese et al.
patent: 4820648 (1989-04-01), Caprioli
patent: 4883597 (1989-11-01), Perlman
patent: 5085499 (1992-02-01), Griffin et al.
patent: 5199295 (1993-04-01), Mettes
H. Stymme et al, "A New Passive Tracer Gas Technique for Ventilation Measurements", Proceedings of 12th AIVC (Air Movement and Ventilation Control Within Buildings) Conference, 24-27 Sep. 1991, Ottawa, Canada, vol. 3, cover page and pp. 1-17.
"Permeation and Diffusion Devices-for the calibration of air monitoring equipment", Thermedics Inc., cover and back pages and pp. 5, 6, and 13-15. published by Dec. --1996.
H. Stymne et al, "Measuring Ventilation Rates in the Swedish Housing Stock", Building and Environment, vol. 29, No. 3, 1994, pp. 373-379.
"Electric Analytical Method" Patent Abstracts of JapanGep P1272, vol. 15, No. 435 Abs pub date Nov. 6, 1991 (3-181850).
Michaelson Peter L.
Noland Thomas P.
Pokotylo John C.
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