Document ID: chunk:federal_register_of_legislation:F2024L00446:reg:16:p55
Version: federal_register_of_legislation:F2024L00446
Segment Type: reg
Provision Reference: reg 16 (pt 55/108)
Character Range: 1039200–1042204

The density of the air ρa shall be calculated using the following equation:
              pb is the total atmospheric pressure, kPa;
                   Ta is the air temperature in the balance environment, Kelvin (K);
                   Mmix is the molar mass of air in a balanced environment, 28.836 g mol-1;
                   R is the molar gas constant, 8.3144 J mol-1 K-1.
              4.3. PN measurement equipment
              4.3.1. Specification
              4.3.1.1. System overview
              4.3.1.1.1. The particle sampling system shall consist of a probe or sampling point extracting a sample from a homogenously mixed flow in a dilution system, a volatile particle remover (VPR) upstream of a particle number counter (PNC) and suitable transfer tubing. See Figure A5/14.
              4.3.1.1.2. It is recommended that a particle size pre-classifier (PCF) (e.g. cyclone, impactor, etc.) be located prior to the inlet of the VPR. The PCF 50 per cent cut point particle diameter shall be between 2.5 µm and 10 µm at the volumetric flow rate selected for particle sampling. The PCF shall allow at least 99 per cent of the mass concentration of 1 µm particles entering the PCF to pass through the exit of the PCF at the volumetric flow rate selected for particle sampling.
              A sample probe acting as an appropriate size-classification device, such as that shown in Figure A5/11, is an acceptable alternative to the use of a PCF.
              4.3.1.2. General requirements
              4.3.1.2.1. The particle sampling point shall be located within a dilution system. In the case that a double dilution system is used, the particle sampling point shall be located within the primary dilution system.
              4.3.1.2.1.1. The sampling probe tip or PSP, and the PTT, together comprise the particle transfer system (PTS). The PTS conducts the sample from the dilution tunnel to the entrance of the VPR. The PTS shall meet the following conditions:
                  (a) The sampling probe shall be installed at least 10 tunnel diameters downstream of the exhaust gas inlet, facing upstream into the tunnel gas flow with its axis at the tip parallel to that of the dilution tunnel;
                  (b) The sampling probe shall be upstream of any conditioning device (e.g. heat exchanger);
                  (c) The sampling probe shall be positioned within the dilution tunnel so that the sample is taken from a homogeneous diluent/exhaust mixture.
              4.3.1.2.1.2. Sample gas drawn through the PTS shall meet the following conditions:
                  (a) In the case that a full flow exhaust dilution system, is used it shall have a flow Reynolds number Re lower than 1,700;
                  (b) In the case that a double dilution system is used, it shall have a flow Reynolds number Re lower than 1,700 in the PTT i.e. downstream of the sampling probe or point;
                  (c) Shall have a residence time ≤ 3 seconds.
              4.3.1.2.1.3. Any