Device for counting particles

Abstract

A device for condensing vapor on condensation nuclei, especially for a particle counter, includes an inlet, via which a gas stream carrying particles as condensation nuclei enters into a feed channel; with a saturation channel. An evaporation unit extends over at least a part of the saturation channel. In the evaporation unit a working liquid can be evaporated in the saturation channel. An outlet leads to a measuring unit. At least one flow passage is provided from the feed channel towards the saturation channel. The at least one flow channel is directed at an angle greater than 90 in relation to a direction in which the feed channel extends.

Claims

1. A device for condensing vapor on condensation nuclei for a particle counter, the device comprising: a feed channel with an inlet, via which a gas stream carrying particles as condensation nuclei enters the feed channel; a saturation channel; an evaporation unit, which extends at least over part of a length of the saturation channel, in which evaporation unit a working liquid can be evaporated in the saturation channel; an outlet, which leads to a measuring unit; a plurality of flow passages from the feed channel towards the saturation channel, the flow passages being distributed uniformly over a circumference of the feed channel, the flow passages being directed at an angle greater than 90 in relation to a feed channel direction corresponding to a direction in which the feed channel extends, the flow passages having a direction component contrariwise a direction in which the feed channel extends, the flow passages being directed at an angle greater than 90 in relation to a flow direction of the saturation channel.

2. A device in accordance with claim 1, wherein the feed channel and the saturation channel are arranged concentrically to one another.

3. A device in accordance with claim 1, wherein: the saturation channel of the evaporation unit is configured in the form of a jacket as a ring channel; the saturation channel is defined radially inwardly by a guide body and radially outwardly by the inner wall of the evaporation unit.

4. A device in accordance with claim 1, wherein the flow passages are directed in relation to the feed channel direction at an angle of up to 180.

5. A device in accordance with claim 1, wherein: a radial flow diameter of flow passages is smaller than a flow diameter of the feed channel; or a radial flow diameter of the flow passages is smaller than a flow diameter of the saturation channel; or a radial flow diameter of the flow passages is smaller than a flow diameter of the feed channel and the radial flow diameter of the flow passages is smaller than a flow diameter of the saturation channel.

6. A device in accordance with claim 1, wherein the at as flow passages in the evaporation unit is configured as a hole in a guide body.

7. A device in accordance with claim 6, wherein the feed channel passes at least partly through the guide body.

8. A device in accordance with claim 1, wherein the evaporation unit has an upper evaporation unit inlet and a lower evaporation unit outlet for feeding and removing the working liquid, the evaporation unit inlet being arranged axially above the evaporation unit outlet.

9. A device in accordance with claim 1, wherein the saturation channel has a homogeneous temperature between 28 C. and 40 C. in case of butyl alcohol as the working liquid and a temperature between 45 C. and 60 C. in case of water as the working liquid.

10. A device in accordance with claim 1, further comprising a condensation unit with a condensation channel.

11. A device in accordance with claim 10, wherein the condensation channel has a homogeneous temperature between 5 C. and 25 C. in case of butyl alcohol as the working liquid and a temperature between 15 C. and 30 C. in case of water as the working liquid.

12. A device in accordance with claim 10, further comprising first nozzle unit provided axially between the evaporation unit and the condensation unit, wherein an inlet opening of the first nozzle unit corresponds to an outlet end of the saturation channel of the evaporation unit and an outlet opening of the first nozzle unit is coaxial to the outlet end of the saturation channel.

13. A device in accordance with claim 12, wherein a cross-sectional area of the outlet opening of the first nozzle unit is smaller than a cross-sectional area of the inlet opening of the first nozzle unit.

14. A device in accordance with claim 12, further comprising another nozzle unit provided axially between the condensation unit and the outlet, wherein a cross-sectional area of an outlet opening of the second nozzle unit is smaller than a cross-sectional area of an inlet opening of the another nozzle unit.

15. A device in accordance with claim 10, wherein the condensation channel is cooled by a cooling device.

16. A particle-measuring device comprising a device for condensing vapor on condensation nuclei, the device comprising: a feed channel with an inlet, via which a gas stream carrying particles as condensation nuclei enters the feed channel; a saturation channel; an evaporation unit, which extends at least over part of a length of the saturation channel, in which evaporation unit a working liquid can be evaporated in the saturation channel; an outlet, which leads to a measuring unit; a plurality of flow passages from the feed channel towards the saturation channel, the flow passages being distributed uniformly over a circumference of the feed channel, the flow passages being directed at an angle greater than 90 in relation to a feed channel direction corresponding to a direction in which the feed channel extends, the flow passages having a direction component contrariwise a direction in which the feed channel extends, the flow passages being directed at an angle greater than 90 in relation to a flow direction of the saturation channel.

17. A device for condensing vapor on condensation nuclei for a particle counter, the device comprising: a feed channel with an inlet, wherein a gas stream carrying particles as condensation nuclei enters the feed channel via the inlet; a saturation channel; an evaporation unit for evaporating a working liquid in the saturation channel, the evaporation unit extending at least over part of a length of the saturation channel; an outlet leading to a measuring unit; a plurality of flow passages in fluid communication with the feed channel and the saturation channel, the flow passages being located between the feed channel and the saturation channel, the flow passages being directed at an angle greater than 90 in relation to a feed channel direction corresponding to a direction in which the feed channel extends, the flow passages being directed at an angle greater than 90 in relation to a flow direction of the saturation channel.

18. A device in accordance with claim 17, wherein the flow passages are distributed uniformly over a circumference of the feed channel, the feed channel extending in a feed channel direction, each of the flow passages extending in a flow passage direction, wherein at least a portion of the flow passage direction is opposite the feed channel direction, the evaporation unit being parallel to the feed channel.

19. A device in accordance with claim 17, wherein an inlet of each of the flow passages is adjacent to an outlet of the feed channel and an outlet of each of the flow passages is located adjacent to the saturation channel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic sectional view through a device according to the present invention; and

(3) FIG. 2 is a cross sectional view through the configuration shown in FIG. 1 at the axial level of a section axis A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) Referring to the drawings, FIG. 1 shows in a sectional view a device 10 according to the present invention for condensation, which may be part of a particle counter (not shown), which has a measuring unit (not shown) in addition to the device 10. In particular, a particle counter, which detects small particles of an aerosol, which act as condensation nuclei, may be arranged downstream of the device 10.

(5) The device 10 has an inlet 11, a connection unit 12, an evaporation unit 13, a first nozzle unit 14, a condensation unit 15, a second nozzle unit 16, and an outlet 17 for the particle flow.

(6) Directions will be described below in a cylindrical coordinate system, whose axial direction corresponds to the longitudinal axis L of the essentially cylindrically symmetrical device 10. The direction in which the longitudinal axis L extends from the inlet 11 to the outlet 17 is called here the axial direction. The axial direction is indicated in FIG. 1 with an arrow at the upper end of the longitudinal axis L. The radial extension is at right angles to the longitudinal axis L; the circumferential extension is at right angles to both above-mentioned directions. The longitudinal axis L is usually at right angles.

(7) The connection unit 12 closes the device 10 downwardly in the axial direction. The inlet 11 of the saturator 13 is coaxial to the longitudinal axis L in the connection unit 12 and opens into a feed channel 18, which is configured as a coaxial hole in the connection unit 12.

(8) The connection unit 12 is connected to the evaporation unit 13. On the axial upper end face, the connection unit 12 has a coaxial guide body 19, which protrudes into the inner space of the evaporation unit 13 coaxially in the direction of the longitudinal axis L. The feed channel 18 passes coaxially through the guide body 19, whose radial dimension approximately corresponds to twice the diameter of the cross section of the feed channel 18. The feed channel 18 protrudes into the guide body 19 about one third of the axial length thereof. This area represents a connection area 34 of the guide body 19, and the rest of the area of the guide body 19 up to its axially upper end is called the deflection area 20.

(9) Distributed in the circumferential direction, four flow passages 24 located at spaced locations from one another in the circumferential direction are formed by cylindrical holes in the guide body 19 at mutually equal radial directions from the longitudinal axis L. These extend here each with an elongated coaxial extension component in relation to the direction of the longitudinal axis L at an angle of about 150 and are directed radially outwardly and axially (opposite the direction of the longitudinal axis L) downwardly. The ends of the flow passages 24 point to a bottom 25 on the axial underside of the evaporation unit 13. Instead of the four flow passages 24, any desired number of flow passages 24 is conceivable. The flow passages 24 open into a cylinder jacket-shaped saturation channel 31, which coaxially surrounds the guide body 19 and is surrounded radially outwardly by an inner wall 26 of the evaporation unit 13 as well as downstream by the wall of the first nozzle unit 14, which is arranged at a radially spaced location from the guide body 19.

(10) The axial top side of the deflection area 20 of the guide body 19 has the shape of a pointed cone. The wall of the first nozzle unit 14 follows the conical deflection area 20 at a radially spaced location. The ring-shaped saturation channel 31 thus passes over first into a cylindrical condensation channel 33 into the condensation unit 15 over the tip of the deflection area 20. The outlet 17, which is further extended in cross section, in the second nozzle unit 16 is connected to the condensation channel 33.

(11) An evaporation part 28 is provided on the radial inner side of the inner wall 26 of the evaporation unit 13 over the entire circumference thereof. This evaporation part is shown only very schematically. The evaporation part 28 is preferably configured with a helical, upwardly open liquid channel for receiving the liquid to be evaporated, as this is described in DE 10 2005 001 992 A1/EP 1 681 549 A2, whose disclosure is made fully the disclosure content of the present disclosure. The evaporation part 28 may have, in principle, another configuration known from the state of the art, especially as this is described as the state of the art in the documents cited or in the methods described in the documents cited.

(12) An inlet 30 is located axially above the evaporation part 28, and an outlet 27 for the liquid to be evaporated is located axially above. The radial inner wall 26 of the evaporation unit 13 is perforated by an outlet 27 leading radially outward at the axial level of the bottom 25. The outlet 27 is configured as a cylindrical hole on the left-hand side of the section of the evaporation unit 13 shown in FIG. 1. Both the inlet 30 and the outlet 27 are located at the same location on the circumference. Both the inlet 30 and the outlet 27 are part of a pumping circuit for transporting the working liquid to be evaporated, which circuit is not shown in greater detail here (reference is thus likewise made to DE 10 2005 001 992 A1/EP 1 681 549 A2).

(13) A jacket-like saturation channel 31 is formed by the radial intermediate space between the evaporation part 28, the outlet 27 and the inlet 30, on the one hand, and the guide body 19 arranged coaxially inside, on the other hand. The saturation channel 31 is defined radially inwardly by the inner wall of the guide body 19 and radially outwardly by an inner wall 29 of the evaporation unit 13 and the evaporation part 28. The radial cross section of saturation channel 31 is larger than the radial cross section of the flow passages 24 and of the feed channel 18.

(14) The saturation channel 31 is heated homogeneously to a temperature between 28 C. and 40 C. by the evaporation part 28 in case of butyl alcohol being used as the working liquid.

(15) As was mentioned, the saturation channel 31 opens in the axial direction at the upper end of the evaporation unit 13 into the channel of the first nozzle unit 14. The first nozzle unit 14 is connected to the evaporation unit 13. In the area of the first nozzle unit 14, the saturation channel 31 points radially inward, in addition to its basically axial extension, so that the channel assumes a circular cross section at the outlet opening 32 of the first nozzle unit 14 and passes over, via an outlet opening of the first nozzle unit 14, into the cylindrical, coaxial condensation channel 33 of the condensation unit 15.

(16) The condensation channel 33 of the condensation unit 15 can be cooled by cooling elements (not shown) to a homogeneous temperature between 5 C. and 25 C. The radial cross section of the condensation channel 33 is constant in the area of the condensation unit 15.

(17) The condensation unit 15 is joined axially upwardly by the second nozzle unit 16, whose axially centered channel has an axially upwardly tapering radial cross section, which finally leads to the outlet 17 of the device 10.

(18) The inlet 30 for the liquid to be evaporated to the evaporation element is used to feed the working liquid to be evaporated, for example, butyl alcohol. The working liquid is at first liquid and is fed into the evaporation unit through the inlet 30 on the axial top side of the evaporation unit 13. The working liquid then enters the area of the evaporation part 28 and flows downward through this or along same, depending on the configuration, at the evaporation part 28 as a consequence of gravity. The working liquid evaporates due to the temperature effect of the heating element, so that at least part of the working liquid enters the area of the saturation channel 31 in the gaseous phase. A non-evaporated portion of the working liquid flows vertically or axially farther downward, reaching the bottom 25 of the evaporation unit 13, where the outlet for the non-evaporated evaporation liquid returns the non-evaporated portion of the working liquid to the pumping circuit and a liquid portion corresponding to the evaporated portion is added to it. It is thus avoided that the non-evaporated portion of the working liquid remains on the bottom 25 of the evaporation unit 13.

(19) FIG. 2 shows a section through a section plane A of FIG. 1 at the axial level of the connection area 34 of the guide body 19. This shows the four flow passages 24 arranged on the circumference. The flow passages are separated from one another in space. Arranged radially between the flow passages 24 and the feed channel 18, the connection area 34 of the guide body 19 is located between the flow passages 24, and the deflection area 20 of the guide body 19 is located radially between the flow passages 24 and the saturation channel 31 in the section plane shown FIG. 2. Further, the cylinder jacket-like configuration of the evaporation part 28 can be seen in FIG. 2 next to the cylinder jacket-like saturation channel 31.

(20) The shape of the cross section of the flow passages 24 shown in FIG. 2 is slightly elliptical, but other configurations, for example, a polygonal cross section, or a cross section varying over the extension direction, are also conceivable.

(21) The procedure employed in the device 10 according to the present invention shall be illustrated below with the use of a gas stream carrying particles:

(22) The particles may be particles with diameters of up to and greater than 1 nm, but especially nanoparticles, i.e., with a spatial dimension of about 1 nm to 100 nm. A gas stream containing the particles, i.e., an aerosol, is introduced into the feed channel via the inlet 11 on the axial underside of the device, and it flows in the direction in which the longitudinal axis L extends, here axially upward. At the of the feed channel 18 the flow reaches the guide body 19 in the evaporation unit 13 and is guided into the four flow passages 24 as a consequence of the pressure generated by the flow. The direction of flow of the gas stream changes by an angle greater than 90, here by 150, as a consequence of the described configuration of the flow passages 24, especially in relation to the feed channel 18.

(23) The aerosol flow is again deflected at the respective end of the flow passages by more than 90 (here at an angle of 150) and it enters the saturation channel 31. At least at this point, the flow is not a laminar flow any longer because of the twofold considerable change in direction (as it may still have been in the feed channel 18) but a turbulent flow, which is not, however, a pronounced turbulent flow and can be called a soft turbulent flow.

(24) A laminar flow of a fluid is characterized in the sense of the present invention in that the fluid (here gas or aerosol) moves in imaginary layers without the layers mixing with one another. By contrast, a turbulent flow has turbulences called turbulent flows and thus contains flow areas that are not directed parallel to the main motion or flow, and separation of flow lines takes place as well. In particular, a turbulently flowing fluid has a rather substantial percentage of flow directions not directed along the flow direction.

(25) As was described, molecules of the working liquid are present in the gaseous phase in the saturation channel 31. The turbulent gas stream moves upward with a main motion direction axially in the saturation channel 31 and is mixed with the gaseous portion of the working liquid as a consequence of the turbulent flows. The degree and the velocity of the mixing with the working liquid are greatly increased compared to a laminar flow as a consequence of the turbulent flows of the gas stream.

(26) Farther axially upward in the flow direction, the saturation channel 31 opens into the channel of the first nozzle unit 14. The channel of the first nozzle unit 14 is configured such that it has a radially inwardly directed component in relation to the longitudinal axis L, so that the channel of the first nozzle unit 14 passes over into the cylindrical coaxial condensation channel 33 of the condensation unit 15 in the area of the outlet opening 32.

(27) The condensation channel 33 is cooled by cooling elements (not shown) of the condensation unit 15 to a temperature between 5 C. and 25 C. This leads to condensation of the evaporated molecules of the working liquid. The particles of the gas stream act as condensation nuclei. As a consequence of the condensation, molecules of the working fluid are deposited on the particles of the gas stream and increase the effective spatial diameter. The now cooled flow enters, as was described, through the outlet of the condensation unit 15 into the second nozzle unit 16, whose radial cross section tapers upward in the axial direction, so that the velocity of the gas stream increases until the gas stream is fed through the outlet 17 of the device 10 to the connected measuring unit (not shown).

(28) Due to the velocity profile of the flow, there is an extensive homogenous mixing with the evaporated portion of the working liquid. The effective spatial dimension of the particles in the flow increases due to the condensation. This change in size is essential for the later detectability of the particles. This change in size is improved by the turbulent flows of the gas stream compared to a laminar flow, as was stated, to a considerable extent.

(29) The lower detection limit for the diameter of the particles to be detected is affected, among other things, by the temperature difference between the temperature of the evaporation element 13 and the temperature of the condensation element 15. Particles with a diameter beginning from 4 nm can be detected at a maximum temperature difference of about 35 C. between the evaporation zone and the condensation zone, but it is also possible, in particular, to configure detections of particle diameters of, e.g., 7 nm, 23 nm, etc., and especially 23 nm to 30 nm. The detectable diameter of the particles becomes smaller due to condensation due to greater temperature differences between the evaporation unit and the condensation unit than in case of smaller temperature differences.

(30) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.