Performance of Nano-DMA Operated with Different Gases for Sheath and Aerosol Carrier Flows

Figures & data

FIG. 1 Schematic diagram of the experimental setup used to evaluate the flow mixing in the NanoDMA when operated with different gases for the sheath and aerosol carrier flow.

FIG. 2 Schematic diagram of the experimental setup used to investigate the sizing accuracy of Nano-DMA operated with different gases for the sheath and aerosol carrier flow.

TABLE 1 Ratios of MTBE (methyl tert-butyl ether) vapor concentration in the monodisperse-aerosol-carrier flow to that in the polydisperse-aerosol-carrier flow when the Nano-DMA operates with different gases for sheath and aerosol-carrier flows (pairing among He, Ar, N₂, and CO₂): 7.5 lpm for the sheath flowrate and 1.5 lpm for the aerosol-carrier flowrate

	Sheath gas
Carrier gas	He	CO2	N2	Ar
He	0.005%	0.21%	0.31%	0.41%
CO2	0.56%	0.0025%	0.12%	0.04%
N2	0.28%	0.11%	0.0012%	0.05%
Ar	0.79%	0.07%	0.07%	0.007%

TABLE 2 Binary diffusivities of different inert gas mixtures (pairing among He, Ar, N₂, and CO₂) and diffusion lengths at flow rates of 7.5 and 15 lpm

	Gas pair
Parameters	N2-Ar	N2-He	He-Ar	N2-CO2	CO2-Ar	CO2-He
Binary gas diffusivity	3.96E-6	2.29E-5	2.72E-5	2.23E-6	2.2E-6	1.05E-5
Diffusion length at sheath
flow 7.5 lpm (cm)	0.16	0.39	0.43	0.124	0.12	0.27
Diffusion length at 15 lpm
sheath flow (cm)	0.116	0.28	0.305	0.087	0.087	0.19

TABLE 3 Ratios of MTBE (methyl tert-butyl ether) vapor concentration in the monodisperse-aerosol-carrier flow to that in the polydisperse-aerosol-carrier flow when the Nano-DMA operates with different gases for sheath and aerosol-carrier flows (pairing among He, Ar, N₂, and CO₂): 15 lpm for the sheath flowrate and 1.5 lpm for the aerosol-carrier flowrate

	Sheath gas
Carrier gas	He	CO2	N2	Ar
He	0.0032%		0.08%	0.05%
CO2	0.21%	0.0054%	0.05%	0.015%
N2	0.11%	0.049%	0.004%	0.03%
Ar	0.31%		0.043%	0.0065%

TABLE 4 Gas properties (viscosity and mean free path) of Ar, N₂, and He at 20°C used in Equation (4)

Properties gas	Viscosity (μ, Kg/m s)	Mean free path (λ, μm)
N2	1.8 × 10^−5	0.0676
Ar	2.29 × 10^−5	0.0722
He	1.993 × 10^−5	0.2

FIG. 3 Comparison of estimated, D_p1, and measured, D_p2, particle sizes for the gas pairs of (a) Ar-Ar and (b) N₂-N₂. The sheath and aerosol-carrier flowrates were kept 15 and 1.5 lpm, respectively. The estimated particle size was based on the gas property of the sheath flow used in the Nano-DMA.

FIG. 4 Comparison of estimated, D_p1, and measured, D_p2, particle sizes when Nano-DMA was operated with the Ar-N₂ composition: (a) Ar as the aerosol-carrier gas and N₂ as the sheath gas; (b) N₂ as the aerosol carrier gas and Ar as the sheath gas. The sheath and aerosol-carrier flowrates were kept at 15 and 1.5 lpm, respectively. The estimated particle size was based on the gas property of the sheath flow used in the Nano-DMA.

FIG. 5 Comparisons of estimated, D_p1, and measured, D_p2, particle sizes when Nano-DMA was operated with the gas combination of He-Ar: (a) Ar as the sheath flow and He as the aerosol carrier flow; (b) He as the sheath flow and Ar as the aerosol carrier flow. The sheath and aerosol-carrier flowrates were kept at 15 and 1.5 lpm, respectively. The estimated particle size was based on the gas property of the sheath flow used in the Nano-DMA.

FIG. 6 Comparisons of estimated, D_p1, and measured, D_p2, particle sizes when Nano-DMA was operated with the combination of He-N₂: (a) N₂ as the sheath flow and He as the aerosol carrier flow; (b) He as the sheath flow and N₂ as the aerosol carrier flow. The sheath and aerosol-carrier flowrates were kept at 15 and 1.5 lpm, respectively. The estimated particle size was based on the gas property of the sheath flow used in the Nano-DMA.