Condensation apparatus

Abstract

The invention provides 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 ( 2 ) and a condenser ( 7 ); the apparatus is 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 size of the particles so that they are capable of being detected by a particle detector.

1 . 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;
 a condenser in fluid communication with the evaporation chamber and having an outlet for connection to a particle detector; 
 a heating element and a porous support each of which is disposed within the evaporation chamber, the porous support carrying thereon a vaporisable substance and the heating element being heatable to vaporise the vaporisable substance to form vapour within the evaporation chamber; wherein the heating element is in direct contact with the porous support; 
 a first inlet for admitting a stream of carrier gas into the evaporation chamber to carry vapour through to the condenser; 
 a second inlet which is downstream of the porous support and through which a stream of sample gas containing gas-entrained particles can be introduced; 
 the apparatus being configured so that condensation of the vaporisable substance onto the gas-entrained particles in the sample gas takes place in the condenser to increase the size of the particles so that they are capable of being detected by a particle detector. 
   
     
     
         2 . An apparatus according to  claim 1  wherein the porous support surrounds the heating element. 
     
     
         3 . An apparatus according to  claim 1  wherein a temperature sensor is disposed within the evaporation chamber. 
     
     
         4 . An apparatus according to  claim 1  wherein the heating element comprises a rod portion and the porous support surrounds the said rod portion. 
     
     
         5 . An apparatus according to  claim 4  wherein the porous support is formed from a porous fabric and comprises a sleeve that fits over the rod portion of the heating element. 
     
     
         6 . An apparatus according to  claim 5  wherein the rod portion of the heating element has a hollow interior within which is disposed a heater wire or heater probe and optionally a thermocouple. 
     
     
         7 . An apparatus according to  claim 6  wherein a thermally conductive filler is used to hold the heater wire or heater probe and the thermocouple (when present) in place. 
     
     
         8 . An apparatus according to  claim 1  wherein the vaporisable substance is selected from dimethyl phthalate, dioctyl phthalate and dimethylsulphoxide. 
     
     
         9 . A condenser configured to be used with an apparatus for increasing the size of gas-entrained particles in order to render the gas-entrained particles detectable by a particle detector;
 the condenser being connectable to said apparatus such that it is in fluid communication with an outlet of an evaporation chamber of the apparatus; and   the condenser having an outlet for connection to the particle detector;   wherein the condenser has a surface area to volume ratio which is greater than the surface area to volume ratio of a cylinder; and the condenser comprises:
 a condenser body having an inlet, an outlet and a hollow interior which has an internal length, an internal width and an internal height; 
 an inlet flow distributor tube connected to the inlet of the condenser body and extending across the internal width of the condenser body; and 
 an outlet flow distributor tube connected to the outlet of the condenser body and extending across the internal width of the condenser body; 
 the internal height of the condenser body being less than a corresponding internal height of each of the inlet and outlet flow distributor tubes; 
 the inlet and outlet flow distributor tubes each being provided in the walls thereof with one or more slots or holes communicating with the hollow interior of the condenser body so as to provide a flow path from the inlet flow distributor tube through the hollow interior of the condenser and into the outlet flow distributor tube. 
   
     
     
         10 . A condenser according to  claim 9  wherein the internal cross sectional area of each flow distributor tube is greater than the internal cross sectional area (internal width×internal height) of the condenser body. 
     
     
         11 . A condenser according to  claim 10  wherein the ratio of the internal cross sectional area of each flow distributor tube to the internal cross sectional area (internal width×internal height) of the condenser body is greater than 1.1 
     
     
         12 . A condenser according to  claim 12  wherein the said ratio is greater than 2. 
     
     
         13 . A condenser according to  claim 9  wherein the walls of the flow distributor tubes with elongate narrow slots that open into the hollow interior of the condenser body and the ratio of the internal height of the container body to the widths of the slots is greater than 1.1. 
     
     
         14 . A condenser according to  claim 9  wherein and the ratio of the internal height of the container body to the widths of the slots is more than 2. 
     
     
         15 . A condenser according to  claim 14  wherein and the ratio of the internal height of the container body to the widths of the slots is greater than 3. 
     
     
         16 . A condenser configured to be used with an apparatus for increasing the size of gas-entrained particles in order to render the gas-entrained particles detectable by a particle detector;
 the condenser in use being in fluid communication with an outlet of an evaporation chamber of the apparatus;   the condenser having an outlet for connection to the particle detector;   wherein the condenser is provided with means for removing condensed substance from the interior walls of the condenser; the said means for removing condensed substance comprising one or more drainage ducts extending along all of part of its length, the drainage ducts being separated from the interior of the condenser by a permeable wall or membrane through which liquid condensate can pass, the drainage ducts having one or more outlets connectable to a pump to extract liquid condensate from the ducts.   
     
     
         17 . A condenser according to  claim 16  wherein the ducts are formed by partitioning the interior of the condenser over at least part of its length by means of one or more longitudinally extending permeable walls or membranes. 
     
     
         18 . A condenser according to  claim 17  wherein the permeable walls or membranes are provided with capillaries that draw condensate from the interior of the condenser into the drainage ducts. 
     
     
         19 . A condenser according to  claim 18  wherein the walls or membranes are formed from (a) a ceramic or stainless steel filter material having a capillary size of <0.1 mm; or (b) a porous material.