Determination of the Clean Air Delivery Rate (CADR) of Photocatalytic Oxidation (PCO) Purifiers for Indoor Air Pollutants Using a Closed-Loop Reactor. Part I: Theoretical Considerations.

Éric Dumont,Valérie Héquet

doi:10.3390/molecules22030407

Abstract

This study demonstrated that a laboratory-scale recirculation closed-loop reactor can be an efficient technique for the determination of the Clean Air Delivery Rate (CADR) of PhotoCatalytic Oxidation (PCO) air purification devices. The recirculation closed-loop reactor was modeled by associating equations related to two ideal reactors: one is a perfectly mixed reservoir and the other is a plug flow system corresponding to the PCO device itself. Based on the assumption that the ratio between the residence time in the PCO device and the residence time in the reservoir τP/τR tends to 0, the model highlights that a lab closed-loop reactor can be a suitable technique for the determination of the efficiency of PCO devices. Moreover, if the single-pass removal efficiency is lower than 5% of the treated flow rate, the decrease in the pollutant concentration over time can be characterized by a first-order decay model in which the time constant is proportional to the CADR. The limits of the model are examined and reported in terms of operating conditions (experiment duration, ratio of residence times, and flow rate ranges).

Highlights

Attention to Indoor Air Quality (IAQ) has greatly increased over the last 30 years
Deviations can be observed at low pollutant concentrations, the use of the exponential fit is preferable for data analysis rather than the linear fit, which requires the careful selection of a few experimental points
Because of recent developments in photocatalytic air cleaning technology, reliable methodologies are needed to assess the performance of commercial PhotoCatalytic Oxidation (PCO) devices, as well as standard tests for consumer safety

Summary

Introduction

Attention to Indoor Air Quality (IAQ) has greatly increased over the last 30 years. The most common gaseous pollutants present in indoor air fall within the concentration range of 1–1000 ppbv. Several hundred volatile organic compounds (VOCs) have been identified. Analysis of the available data demonstrates a statistical association between IAQ conditions and occupants’. The traditional dilution method of ventilation is not always recommended in current practice due to its limitation in terms of outdoor air quality and energy cost [2] while the control of pollutant emissions is not always possible. It appears necessary to develop technologies and effective strategies to improve IAQ

Objectives

Findings

Discussion

Conclusion