Numerical and experimental investigation on the performance of a ventilated chamber for low-cost PM sensor calibration

Abstract

Particulate matter (PM) sensors are popular for distributed monitoring due to their portability, low-cost and networking capabilities. To provide reliable data, these sensors have to be calibrated periodically in the laboratory. This is often done in chambers with several of them co-located, alongside several research grade instruments. It is important to confirm that the aerosol is well distributed to ensure reliability and accuracy of the calibration tests. This paper describes a modeling and experimental study of these chambers used for calibration of PM sensors. The experimental setup is described and calibration results for the low-cost PM sensors (MAXIMA sensor, Applied Particle Technology, Inc.) using research-grade instruments (GRIMM 11-C, GRIMM Technologies, Inc.) are presented. A computational fluid dynamics (CFD) model including effects of turbulence and Brownian motion is used to predict particle trajectories and distribution in the chamber. The simulated particle number concentration agrees well with the measured values in the chamber. Having the CFD model, the suitability of three proposed chamber designs (fan off; fan on-parallel; fan on-diagonal) are explored for a variety of conditions. Operating conditions that result in uniform concentrations are established using the model. The recommended design for the PM sensor calibration in a rectangular ventilated chamber is: parallel fan layout, fan pressure of 12 Pa, and inlet air flow rate between 10 and 15 L/min. This study shows that the numerical modeling is available to understand the performance of a calibration chamber as well as optimizing the chamber design. A broader perspective is that the results validate the use of low-cost PM sensors for checking the distribution of aerosols in chambers.