Determination of the Clean Air Delivery Rate (CADR) of Photocatalytic Oxidation (PCO) Purifiers for Indoor Air Pollutants Using a Closed-Loop Reactor. Part II: Experimental Results
Abstract
:1. Introduction
2. Model
3. Experimental Methods
3.1. Recirculation Closed-Loop System
3.2. PCO Device
3.3. VOC Generation and Analytical Methods
3.4. Operating Conditions
4. Results and Discussion
4.1. CADR Determination
4.2. Effect of the Light Irradiance Intensity
4.3. Effect of the Flow Rate
4.4. Effect of the Initial Concentration
5. Conclusions
- (i)
- Since the volume of the PCO device is very small in relation to the volume of the reservoir, the ratio of the residence times (τP/τR) tends to zero, and consequently, the concentration-time relationship given by Equation (1) can be used to model the experimental points. Moreover, as the term α is usually determined to be lower than 5%, the simplified model characterized by a first-order decay model (Equation (3)) can be used to determine the CADR of the PCO device.
- (ii)
- Since the Excel® solver is easily usable for data analysis, such a tool should be preferred for CADR determination rather than the analysis of the curve ln(C/C0) vs. time, which involves selecting a given number of points for a correct calculation.
- (iii)
- According to the operating conditions, the CADR ranged from 0.35 to 3.95 m3·h−1, i.e., one order of magnitude for the same PCO device. The CADR was mainly dependent on the light irradiance intensity. An increase in the CADR with the square root of the light irradiance was observed.
- (iv)
- Although the CADR of the PCO device inserted in the closed-loop reactor did not theoretically depend on the flow rate (see Part I), the experimental results did not enable the confirmation of this point. The results were contrasting. Some experimental data were in agreement with the theory, whereas others disagreed. Further investigations are therefore needed to explain this ambiguity. Numerical simulations of the air stream line and velocity through the medium may be useful.
- (v)
- The maximum degradation rate rmax ranged from 342 to 4894 ppbv·h−1. As the initial concentration is one parameter influencing the degradation rate of the pollutant, tests should be performed at a given value of the initial concentration in order to compare the performances of different types of PCO apparatus.
Acknowledgments
Author Contributions
Conflicts of Interest
Abbreviations
A | cross-sectional area of the PCO device (m2) |
C | pollutant concentration (mol·m−3) |
CADR | Clean Air Delivery Rate (m3·s−1) |
E | efficiency (dimensionless) |
k | overall degradation rate constant (s−1) |
L | length of the PCO device (m) |
Q | flow rate (m3·s−1) |
r | degradation rate (mol m−3·s−1) |
t | time (s) |
tc | time constant of the closed-loop reactor (s) |
VP | PCO device volume (m3) |
VR | reservoir volume (m3) |
Greek letters | |
τP | residence time in the PCO device (s) |
τR | residence time in the reservoir (s) |
α | fractional yield of the treated flow rate (dimensionless) |
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Experimental Conditions | Experimental Results | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
I (mW·cm−²) | v (m·s−1) | τR (s) | C0 (ppbv) | α (−) | R2 | CADR (m3·h−1) | 1/α (−) | tc (h) | tc (s) | rmax (ppbv·h−1) | |
Exp 1 | 0.10 | 0.2 | 52.5 | 600 | 0.0278 | 0.988 | 0.80 | 36 | 0.53 | 1917 | 1140 |
Exp 2 | 0.10 | 0.6 | 17.5 | 200 | 0.0086 | 0.973 | 0.74 | 117 | 0.57 | 2052 | 342 |
Exp 3 | 0.10 | 0.6 | 17.5 | 1000 | 0.0043 | 0.956 | 0.37 | 232 | 1.13 | 4065 | 890 |
Exp 4 | 0.10 | 1.0 | 10.5 | 600 | 0.0059 | 0.937 | 0.85 | 169 | 0.49 | 1781 | 1183 |
Exp 5 | 0.35 | 0.2 | 52.5 | 200 | 0.0337 | 0.969 | 0.97 | 30 | 0.44 | 1584 | 449 |
Exp 6 | 0.35 | 0.2 | 52.5 | 1000 | 0.0259 | 0.927 | 0.75 | 39 | 0.57 | 2055 | 1780 |
Exp 7 | 0.35 | 0.6 | 17.5 | 600 | 0.0166 | 0.971 | 1.43 | 60 | 0.30 | 1062 | 2045 |
Exp 8 | 0.35 | 0.6 | 17.5 | 4700 | 0.0041 | 0.964 | 0.35 | 244 | 1.19 | 4273 | 3962 |
Exp 9 | 0.35 | 1.0 | 10.5 | 200 | 0.0118 | 0.961 | 1.70 | 85 | 0.25 | 901 | 786 |
Exp 10 | 0.35 | 1.0 | 10.5 | 1000 | 0.0090 | 0.984 | 1.30 | 111 | 0.33 | 1171 | 3097 |
Exp 11 | 0.35 | 1.9 | 5.5 | 600 | 0.0047 | 0.966 | 1.29 | 212 | 0.33 | 1173 | 1841 |
Exp 12 | 0.60 | 0.2 | 52.5 | 600 | 0.0643 | 0.994 | 1.85 | 16 | 0.23 | 843 | 2639 |
Exp 13 | 0.60 | 0.6 | 17.5 | 200 | 0.0457 | 0.991 | 3.95 | 22 | 0.11 | 392 | 1827 |
Exp 14 | 0.60 | 0.6 | 17.5 | 1000 | 0.0170 | 0.929 | 1.47 | 59 | 0.29 | 1039 | 3505 |
Exp 15 | 0.60 | 1.0 | 10.5 | 600 | 0.0167 | 0.969 | 2.40 | 60 | 0.18 | 635 | 3971 |
Exp 16 | 1.00 | 0.6 | 17.5 | 600 | 0.0238 | 0.979 | 2.06 | 42 | 0.21 | 743 | 2934 |
Exp 17 | 2.00 | 0.6 | 17.5 | 600 | 0.0397 | 0.962 | 3.43 | 25 | 0.12 | 449 | 4894 |
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Héquet, V.; Batault, F.; Raillard, C.; Thévenet, F.; Le Coq, L.; Dumont, É. Determination of the Clean Air Delivery Rate (CADR) of Photocatalytic Oxidation (PCO) Purifiers for Indoor Air Pollutants Using a Closed-Loop Reactor. Part II: Experimental Results. Molecules 2017, 22, 408. https://doi.org/10.3390/molecules22030408
Héquet V, Batault F, Raillard C, Thévenet F, Le Coq L, Dumont É. Determination of the Clean Air Delivery Rate (CADR) of Photocatalytic Oxidation (PCO) Purifiers for Indoor Air Pollutants Using a Closed-Loop Reactor. Part II: Experimental Results. Molecules. 2017; 22(3):408. https://doi.org/10.3390/molecules22030408
Chicago/Turabian StyleHéquet, Valérie, Frédéric Batault, Cécile Raillard, Frédéric Thévenet, Laurence Le Coq, and Éric Dumont. 2017. "Determination of the Clean Air Delivery Rate (CADR) of Photocatalytic Oxidation (PCO) Purifiers for Indoor Air Pollutants Using a Closed-Loop Reactor. Part II: Experimental Results" Molecules 22, no. 3: 408. https://doi.org/10.3390/molecules22030408