Patent Description:
Existing technology in this field is believed to have significant limitations and shortcomings. For example, systems used to modify particle properties by vapor exposure require long sample paths (for cylindrical conduits) or cumbersome flow geometry (for rectangular conduits). The additional length and flow geometries increase the response time of these devices as well as increase particle deposition to the walls of the flow conduit.

<CIT> discloses an apparatus for increasing the size of gas-entrained particles in order to render the gas-entrained particles detectable by a particle detector, the apparatus comprising an evaporation chamber and a condenser configured so that vapour-laden gas from the evaporation chamber can flow into the condenser, and condensation of the vaporisable substance onto gas-entrained particles in the condenser takes place to increase the particle size.

<CIT> discloses a parallel passage fluid contactor structure for chemical reaction processes has one or more segments, where each segment has a plurality of substantially parallel fluid flow passages oriented in an axial direction; cell walls between each adjacent fluid flow passages and each cell wall has at least two opposite cell wall surfaces.

Furthermore, a summary of the state of the art is provided by <NPL>.

According to the present invention, there is provided a particle vapor reactor according to appended Claim <NUM>.

The present invention provides particle-vapor reactor (PVR) apparatus which is practical, reliable, accurate and efficient, and which are believed to constitute an improvement over the background technology.

The invention relates to an apparatus where the aerosol is introduced to the device using a cylindrical conduit that transitions to a rectangular conduit in a manner that limits flow separation. The properties of the conduit walls may be different than that of the aerosol for the purpose of modifying the gas properties within the aerosol. The sample aerosol occupies the entire cross section of the conduit or is sheathed by a gas having different properties than the aerosol. The aerosol sample exits the device from a rectangular conduit or the sample is transitioned to a cylindrical conduit. The conduit may be fabricated from porous material, a sintered polymer or metal, or using composite porous aluminum (such as METAPOR™). The invention may be used in a device where the number concentration (partial pressure) of a vapor is modified within an aerosol.

The invention may be used in a PVR where the partial pressure of a vapor is greater than the partial pressure of that vapor over a flat surface composed the vapor's condensed phase (Supersaturation). For particles larger than a critical diameter, the vapor molecules condense onto the particles resulting in an increase of the particle diameter by orders of magnitude. The enlarged droplet/particle entities are easily detected using common light scattering methods and with knowledge of the counting rate and aerosol flow, a particle concentration can be calculated. At sufficiently high supersaturation levels, the condensation process will initiate for particles which are too small to be detected using optical methods typically employed for single aerosol particle counting. For instance, supersaturation may be achieved via diabatic heat and mass transfer which is known within literature, for example by<NPL>.

The invention may be used in a PVR where the partial pressure of a vapor is less than the partial pressure of that vapor over a flat surface composed the vapor's condensed phase (Subsaturation). This device can be used to raise or lower the vapor pressure within an aerosol to study sorption related phenomena and or chemical reactions between particles and vapor molecules.

The present invention is believed to involve novel elements, combined in novel ways to yield more than predictable results. The problems solved by the invention were not fully recognized in the prior art.

The aspects, features, advantages, benefits and objects of the invention will become clear to those skilled in the art by reference to the following description, claims and drawings.

<FIG> shows a Condensation Particle Counter (CPC) <NUM> including a saturator <NUM> with a sample input end <NUM>, a condenser <NUM>, and an optical detector <NUM>. A fill pump <NUM> is connected to the saturator <NUM>. A fluid supply <NUM> (containing for example Butanol) is connected to the fill pump <NUM> and also communicatively to a drain pump <NUM>. The drain pump <NUM> is also connected to the saturator <NUM>. A sheath pump <NUM> is connected to the input end <NUM> and to a filter <NUM>. A transport pump <NUM> is connected to the optical detector <NUM>. A high/low flow valve <NUM> is communicatively connected to the optical detector <NUM>, transport pump <NUM>, input end <NUM> and sheath pump <NUM>.

<FIG> show a first embodiment of the Condensation Particle Counter (CPC) <NUM> of the invention. The CPC <NUM> includes a Particle-Vapor Reactor (PVR) <NUM>, an aerosol inlet <NUM>, a fluid supply section <NUM>, a heating section <NUM>, and an optical detection section <NUM>. In this embodiment, the CPC <NUM> includes sample sheathing functionality. The fluid supply section <NUM> includes a liquid supply <NUM>, a sheath inlet <NUM>, a transport outlet <NUM>, and a vent <NUM>. The PVR <NUM> amplifies the size of Nano-particles for optical detection in section <NUM>.

Referring also to <FIG>, in this embodiment of the invention, the PVR <NUM> has an elongated body of a predetermined length. The body wall defines an inner, longitudinally oriented fluid flow conduit or lumen which extends from an input end (shown disposed at the lower or bottom end in the drawings) and an outlet end (shown disposed at the upper or top end in the drawings). The PVR <NUM> conduit has a conditioner or saturator section <NUM> and a growth or condenser section <NUM>. The sections <NUM> and <NUM> are separated in this embodiment of the PVR <NUM> by a separator <NUM>. The separator <NUM> thermally and electrically insulates the conditioner and growth sections <NUM> and <NUM> from each other. Further, each section <NUM> and <NUM> are preferably constructed of separate but connected lateral members <NUM> A/B and <NUM> A/B.

In the CPC <NUM>, aerosol is introduced into the conditioner section <NUM> of the PVR <NUM> using a cylindrical conduit geometry <NUM> that transitions to a rectangular conduit geometry <NUM> (as best shown in <FIG>) in a manner that limits flow separation. The properties of the conduit walls differ than that of the aerosol for the purpose of modifying the gas properties within the aerosol. The conduit members 70A/B and 72A/B is preferably fabricated from porous material such as sintered polymer or metal, or using composite porous aluminum (Metapor ™). The sample aerosol is preferably sheathed by a gas having different properties than the aerosol. The aerosol sample exits the growth section <NUM> of the device <NUM> by transitioning from a rectangular conduit to a cylindrical conduit. In this embodiment, the number concentration (partial pressure) of a vapor is modified within an aerosol.

Although the aerosol is disclosed as being sheathed in this embodiment, it is within the purview of the invention may be unsheathed, and occupy the entire crossection of the conduit. An example of a CPC operating unsheathed is shown in <FIG>. Further, although the aerosol transitions from a rectangular geometry to a circular geometry upon exit, it is within the purview of the invention that it may exit at a rectangular geometry.

In one mode of use, the partial pressure of a vapor is greater than the partial pressure of that vapor over a flat surface composed the vapor's condensed phase (Supersaturation). For particles larger than a critical diameter, the vapor molecules condense onto the particles resulting in an increase of the particle diameter by orders of magnitude. The enlarged droplet/particle entities are easily detected using common light scattering methods via the detector section <NUM>. And, with for a given counting rate and aerosol flow rate, a particle concentration is calculated. At sufficiently high supersaturation levels, the condensation process will initiate for particles which are too small to be detected using optical methods typically employed for single aerosol particle counting. In this embodiment, supersaturation is achieved via known diabatic heat and mass transfer processes.

In another mode of use, the partial pressure of a vapor is less than the partial pressure of that vapor over a flat surface composed the vapor's condensed phase (Subsaturation). This embodiment of the particle-vapor reactor can be used to raise or lower the vapor pressure within an aerosol to study sorption related phenomena and or chemical reactions between particles and vapor molecules.

<FIG> shows a modification to the bottom end of the CPC <NUM>, forming an alternative embodiment, CPC <NUM>, whereby the CPC <NUM> operates in an unsheathed mode.

<FIG> is a photograph of an alternative embodiment of the PVR <NUM> including one half of a continuous wick section, wherein the conditioning and growth sections are unitary. This longitudinally unitary embodiment of the PVR <NUM> is preferably machined from porous aluminum, for example METAPOR™ porous aluminum.

<FIG> show computational fluid mechanics results for the CPC and PVR of <FIG>. <FIG> shows the saturation ratio within a sheathed PVR fluid section. In this model, the sheath and aerosol flows are each <NUM><NUM>/min. <FIG> show path lines of the aerosol flow within the sheathed device.

A second embodiment of the CPC <NUM><NUM> is shown in <FIG>. The CPC <NUM> includes a PVR <NUM>, an aerosol inlet <NUM>, a fluid supply section <NUM>, a heating section <NUM>, and an optical detection section <NUM>. In this embodiment, the CPC <NUM> includes sample sheathing functionality. The fluid supply section <NUM> preferably includes liquid supply, a sheath inlet, a transport outlet and a vent ingress/egress means. Such means may be associated with pumps. The PVR <NUM> functions include amplifying the size of Nano-particles for optical detection in section <NUM>.

Referring also to <FIG>, in this embodiment of the invention, the PVR <NUM> also has an elongated body of a predetermined length. The body wall defines an inner, longitudinally oriented fluid flow conduit which extends from an input end (shown disposed at the lower or bottom end in the drawings) and an outlet end (shown disposed at the upper or top end in the drawings). The PVR <NUM> conduit has a saturator or saturation section <NUM> and a 110condensor section <NUM>. The sections <NUM> and <NUM> are separated laterally in this embodiment of the PVR by a separator <NUM>. The separator <NUM> thermally and electrically insulates the conditioner and growth sections <NUM> and <NUM> from each other. Further, each section <NUM> and <NUM> is preferably constructed of separate but connected lateral members <NUM> A/B and <NUM> A/B divided along their longitudinal axis.

The CPC <NUM> and PVR <NUM> function as follows. An analyte is continuously aspirated into a cylindrical conduit AI where a portion of the analyte near the conduit walls acting as a transport flow is axisymmetrically aspirated from the conduit at ST. The remaining analyte passes through a sample conduit at SC. The transport flow is filtered to remove particles and a prescribed volumetric rate is axisymmetrically reintroduced around the sample conduit as a sheath flow at SM. The sheath flowrate is nominally equivalent to the transport flowrate. Optionally, a flow valve (for example, a flow rate valve <NUM> as shown in <FIG>) may used to optionally operate the system <NUM> at a transport flowrate above the sheath flowrate.

The sheathed sample exits a cylindrical conduit at SS and enters the saturator section <NUM> a region at TR where the cross section of the conduit transitions from circular to obround. Starting at this transition, the conduit is fabricated from a material that supplies a liquid film at the wall surface such as a porous metal, felt, membrane, or porous plastic WI and W11. The liquid is preferably provided by a push/pull pumping system where a communicatively connected liquid supply pump (not shown) injects liquid from a supply bottle or the like (not shown) to the base of the porous section at BI and a communicatively connected drain pump (not shown) removes the liquid at BE and returns it to the supply bottle. The drain rate is greater than the supply rate which ensures that a minimal volume of liquid is present in the system. Liquid is also confirmed by monitoring the increased conductivity between F1 and the outer metal surface of the porous conduit when liquid is present. The liquid at the surface maintains a saturated vapor pressure that diffuses into the sheathed sample flow while simultaneously the temperature of the flow is modulated to the wall temperature. The wall temperature is controlled using heaters <NUM> installed at H1 and H2. The saturator section <NUM> is sufficiently long so that the vapor pressure and temperature of sheathed sample flow reach design conditions. For the device described herein the design conditions are a Log Mean Temperature Difference (LMTD) <<NUM>% and a Saturation Ratio (S = Vapor pressure / Saturated Vapor Pressure) > <NUM>.

Following the saturator section, the sheathed sample enters the condenser section <NUM> where the conduit walls are maintained at a prescribed temperature. The saturator and condenser conduits are separated by a short conduit fabricated from a thermally insulating and static dissipative material at SP. As the sheathed sample traverses the condenser section <NUM> the temperature and vapor pressure of the flow modulates to the match the wall conditions. The wall temperature in the condenser section <NUM> is controlled using thermoelectrics devices installed at T1 and T2. Supersaturation is achieved by exploiting the Lewis number (Le) for the system (Le = ratio of thermal diffusivity to vapor diffusivity). For systems where Le > <NUM> the condenser walls are held at a lower temperature than the bulk temperature of the flow. This results in the temperature of the flow decreasing at a faster rate than the vapor pressure. The resulting ratio of the actual vapor pressure to the saturated vapor pressure calculated from the gas temperature is referred to as the Saturation ratio (S). The supersaturated vapor will then condense onto sufficiently large particles within the sheathed sample flow. The system is designed such that following supersaturation, the total condensed vapor onto the particles is controlled by reducing the residence time of the particles in this region. Controlling the amount of condensed vapor will reduce modulation of the temperature and vapor pressure caused by high particle concentrations.

Near the exit of the condenser section <NUM> the conduit transitions from an obround to circular shape at TE. The transition back to cylindrical flow at SE is done to facilitate focusing the sample stream at nozzle N1. The flow then enters an optical detection device OP where the sample passes through a region with incident electromagnetic radiation that is scattered by the presence of a sufficiently large object (in this case, a particle with condensed vapor). The scattered radiation is detected by a sensor and is registered as a detected particle by the device.

<FIG> shows detailed drawings of the porous sections <NUM> A and B, and <NUM> A and B. For the device described herein the condenser <NUM> conduit is fabricated using a porous metal (Metapor™). In the saturator section <NUM> a porous plastic sheet (Fritware from SP Scienceware) W11 is inserted into the porous metal housing to provide a higher pore density for supplying liquid at the surface. The angles of the transition regions are designed so that flow separation does not occur.

<FIG> is a graph shows a plot of the temperature and vapor pressure as a function of axial position for an obround (PP) versus circular (Circ) saturator cross section. For the comparisons in <FIG>, the conduit velocity was fixed at <NUM>/s, sheathed sample flowrate was set a <NUM><NUM>/sec and the aspect ratio (obround width to height) was set to <NUM>. The plots clearly show the advantage gained in the shorter overall length in the obround device for equivalent plug flow velocities. For the device described herein, the saturator section is designed so that the flow reaches a bulk mean saturation ratio of <NUM> with the center of the flow being below the mean and the flow near the walls being above it. The purpose of this is to provide a uniform peak supersaturation across the flow conduit which facilitates a sharper detection cutoff as a function of size. This practice also applies for the circular conduit.

<FIG> is a graph showing a plot of the temperature and vapor pressure as a function of axial position for the condenser section.

<FIG> and <FIG> show computational fluid mechanics results (contours of saturation ratio S) for the saturation ratio within a sheathed PVR fluid section. In this model, the sheath and aerosol flows are each <NUM><NUM>/min.

<FIG> shows computational fluid mechanics results (contours of vapor pressure in Pa) for the vapor pressure.

<FIG> shows path lines of the aerosol flow within the sheathed device.

<FIG> shows a modification to the bottom end of the CPC <NUM><NUM>, forming an alternative embodiment of the CPC <NUM>, whereby the CPC <NUM> operates in an unsheathed mode.

Claim 1:
A particle vapor reactor (<NUM>) comprising a reactor body with a fluid flow conduit having an inlet end and an outlet end, the cross-section of the conduit having a circular geometry at the inlet end, a rectangular geometry at a midsection and a circular geometry at its outlet end,
characterized in that
said circular geometry at the inlet end transitions from circular to obround, and wherein said circular geometry at the outlet end transitions from obround to circular,
wherein the fluid flow conduit has a saturator section (<NUM>) disposed towards the inlet end and a condenser section (<NUM>) disposed towards the outlet end, and
wherein the conduit is elongated and constructed of two lateral half portions (120A, 120B, 122A, 122B), the lateral half portions (120A, 120B, 122A, 122B) being joined along the longitudinal axis of the reactor (<NUM>).