Coupled Gas Flow, Diffusion and Reaction in a ppb-level SnO2-NiO Formaldehyde Sensor System

K Darcovich,J Dunford,J Tunney,L Styles,A Constant,G Xiao

doi:10.1260/1750-9548.5.2.101

Abstract

The present project is part of an effort towards the development of a ppb-level formaldehyde sensor system for indoor air quality. An electroceramic response model for a SnO 2 -NiO composite solid oxide sensing material of n -type conductivity inside the porous material is coupled with a transient flow field simulation of the delivery of a formaldehyde pulse to the sensor surface. Coupled volumetric CFD domains are used to examine the effects of the transport of formaldehyde from a preconcentrator unit to the sensor, and its implications for interpreting the sensor signals from laboratory experiments.

Highlights

Semiconducting solid oxides have been long established as materials useful for gas sensing applications
An electroceramic response model for a SnO2-NiO composite solid oxide sensing material of ntype conductivity inside the porous material is coupled with a transient flow field simulation of the delivery of a formaldehyde pulse to the sensor surface
The HCHO is slow to diffuse into the sensor and the concentration in the sensing domain is closer in value to points in the flow domain well forward of the sensor position

Summary

INTRODUCTION

Semiconducting solid oxides have been long established as materials useful for gas sensing applications. The use of metal oxide materials for the detection of atmospheric and industrial gases including volatile organic compounds has long been established, with materials based on SnO2, TiO2 and ZnO commonly used as gas sensors [5]. These materials are typically n-type semiconductors, which when exposed to reducing gases such as aldehydes, ketones or alcohols will show an increase in conductivity by reacting with chemisorbed oxygen species on the surface causing electrons to be injected into the conduction band of the material. While the overall project is broad in scope, targeting a wireless sensing network integrated with building heating, ventilation and air conditioning for enhanced indoor air quality and energy efficiency, the material presented here relates to the development and implementation of an SnO2-NiO solid oxide sensor in a dynamic environment

PHYSICAL SYSTEM

SENSOR

MODEL CALIBRATION AND VALIDATION

RESULTS AND DISCUSSION

CONCLUSIONS