Method and apparatus for determining a concentration of aerosol particles in a carrier gas

A method for determining a concentration of aerosol particles in a carrier gas, comprising the steps:

• a) provision of an aerosol which has aerosol particles in a carrier gas comprising at least one condensable component;
• b) introduction of at least part of the aerosol into a chamber of a pressure-rated vessel, wherein the chamber is delimited by at least one wall, wherein the at least one wall adjoining the chamber is set to a temperature which is above a saturation temperature of at least one condensable component;
• c) subsequent removal of part of the aerosol from the chamber as a result of which a decrease in pressure in the chamber occurs, as a result of which the at least one condensable component condenses at least partly on the aerosol particles;
• and
• d) determination of a concentration of aerosol particles in the carrier gas during removal of the part of the aerosol from the chamber,
• wherein the wall adjoining the chamber is set to a temperature below a freezing temperature of the at least one condensable component, as a result of which a proportion of previously liquid aerosol particles freezes during step b) and a proportion of frozen aerosol particles is obtained thereby.

An apparatus for determining a concentration of aerosol particles in a carrier gas, comprising

• a pressure-rated vessel for accommodating an aerosol which comprises aerosol particles in a carrier gas comprising at least one condensable component, wherein the vessel has at least one chamber for accommodating the aerosol, an inlet into the chamber and an outlet from the chamber and the chamber is delimited by at least one wall, wherein the at least one wall adjoining the chamber can be set to a temperature which is above a saturation temperature of the at least one condensable component and the chamber has a length fin the flow direction of the aerosol and a ratio of the length f to a maximum diameter d of the chamber perpendicular to the flow direction is such that 5>f/d>0.2
• a pump apparatus for taking part of the aerosol off from the chamber, wherein the pump apparatus has a pump conduit which is installed at the outlet from the chamber;
• a measurement device for determining a concentration of the aerosol particles in the carrier gas, wherein the measurement device is installed in the pump conduit at the outlet from the chamber;
• and
• a control unit for controlling the concentration of the at least one condensable component in the aerosol, the temperature of the at least one wall adjoining the chamber, the removal of the aerosol from the chamber and the measurement device.