Experimental characterization of particle wall-loss behaviors in UCR dual-90m³ Teflon chambers

Figures & data

Table 1. List of experiments used in this study.

Run Number	Time (min)	Particle Composition	Particle Size	Max Particle Loading (cm^−3)	Notes
2429A	339	Ammonium Sulfate	Polydisperse	3.35E4	Neutralized particles
2429B	339	Ammonium Sulfate	Polydisperse	1.95E4	Neutralized particles
2430A	300	Ammonium Sulfate	Polydisperse	2.60E4	Neutralized particles
2430B	300	Ammonium Sulfate	Polydisperse	1.20E4	Neutralized particles
2431A	405	Ammonium Sulfate	Polydisperse	3.00E3	Neutralized particles
2432A	493	Ammonium Sulfate	Polydisperse	1.65E4	Neutralized particles
2479B	480	Ammonium Sulfate	50 & 200 nm	4.10E2	Neutralized particles
2482B	360	Ammonium Sulfate	50 & 300 nm	3.70E2	Neutralized particles
2483B	360	Ammonium Sulfate	50 & 400 nm	1.80E2	Neutralized particles
2487B	427	Ammonium Sulfate	50 & 200 nm	2.10E2	Neutralized particles
2489B	360	Ammonium Sulfate	50 nm	4.80E2	Neutralized particles
2492B	385	Ammonium Sulfate	100 nm	2.90E2	Neutralized particles
2497B	544	Ammonium Sulfate	50 & 200 nm	2.10E2	Positively charged particles only, dual-SMPS system
2498B	586	Ammonium Sulfate	50 & 200 nm	2.10E2	Neutralized particles, dual-SMPS system
2530B	575	Ammonium Sulfate	50 & 200 nm	5.30E2	Negatively charged particles only, dual-SMPS system
2532B	554	Ammonium Sulfate	50 & 200 nm	3.00E1	Neutral particles only, dual-SMPS system
Mez091020	415	Ammonium Sulfate	Polydisperse	1.40E5	Neutralized particles
Mez091220	459	Ammonium Sulfate	Polydisperse	5.80E4	Neutralized particles
Mez091420	486	Ammonium Sulfate	Polydisperse	3.60E4	Neutralized particles
Mez091620	362	Ammonium Sulfate	Polydisperse	3.30E3	Neutralized particles

Figure 1. Schematic diagrams of the experimental set-up options. Initial particles could be prepared as: (a) all positively charged, (b) all negatively charged, (c) at charge equilibrium (neutralized), (d) no particle charges (neutral).

Table 2. Single-size particle charge distribution at Fuchs’ charge equilibrium.

Diameter	−3	−2	−1	0	+1	+2	+3
50 nm	–	0.89%	22.29%	59.05%	17.25%	0.52%	–
200 nm	3.54%	12.53%	25.37%	29.36%	19.42%	7.35%	1.59%

Figure 2. (a) Averaged monodisperse particle decay rates as a function of size in UCR collapsible chambers and (b) Fuchs’ total charge percentage as a function of particle size.

Figure 3. Dual-SMPS measurements on monodisperse particle wall-loss at two typical sizes, (a) 50 nm and (b) 200 nm during a characterization experiment. The blue curves represent normalized total particle number concentrations, measured by SMPS with charger; the red curves represent normalized positively-charged particle number concentrations, measured by SMPS without charger; (c) 50 nm total particle decay rates in four quartiles from the five selected characterization experiments.

Figure 4. Dual-SMPS measurements on monodisperse particle wall-loss at two typical mobility sizes, 50 and 200 nm, during three typical types of characterization experiments. (a) Neutral-only, (b) positively-charged only and (c) negatively charged only particles were injected to the chamber, respectively. The blue/teal curves were measured by SMPS with charger while the red/pink curves were measured by SMPS without charger, detecting only the positively charged particles suspended in the chamber. The red/pink curves in (a1), (a2), (c1) and (c2) are visually scaled up by 4 times on the right-hand side y-axis.

Figure 5. Comparison of the averaged size-dependent measured particle loss pattern obtained from polydisperse experiments (black curve) and the averaged size-dependent coagulation-free particle wall-loss pattern obtained from monodisperse experiments (blue curve) in UCR 90-m³ collapsible chambers.

Figure 6. Averaged size-dependent measured particle loss patterns from experiments designed with increased particle number loadings (in units of cm⁻³) in UCR 37.5-m³ chamber.

Figure 7. Inter-comparison of averaged size-dependent particle number loss patterns among different chamber facilities or calculations. “Measured” represents measured particle loss (including particle wall-loss and coagulation); “Coagulation-corrected” represents particle wall-loss rates that are post-corrected with theoretical coagulation rates; and “Coagulation-free” represents particle wall-loss rates obtained from monodisperse particle injection experiments in this study, where coagulation is negligible due to their low particle number loadings.