Performance of nanofiber/microfiber hybrid air filter prepared by wet paper processing

Figures & data

Figure 1. Schematic of laboratory-scale paper production process based on the Japanese Industrial Standard JIS-P8222 (2005).

Table 1. Nanofiber geometrical properties.

	Geometric mean diameter, dfg [µm]	Geometric standard deviation, σg [−]	Variance of fiber diameter, σ [−]	Mean diameter, df [μm]*
Nanofiber a	0.151	1.804	0.595	0.180
Nanofiber b	0.195	1.840	0.510	0.234
Microfiber	11.7	–	–	11.7
Binder (PVA)	11.5	–	–	11.5

* d_f = d_fgexp(0.5ln²σ_g).

Figure 2. SEM micrograph of NF-a (30%)/MF composite filter.

Figure 3. Experimental setup for measuring the pressure drop and penetration of the test filter (DMA: differential mobility analyzer, CPC: condensation particle counter, and MFC: mass flow controller).

Figure 4. Pressure drops of the tests filters as a function of mixing fraction.

Table 2. Pressure drop and inhomogeneity factor of the mixed filter (α = 0.06, u = 0.053 m s⁻¹).

x [−]	NF-a			NF-b
	Δp^f [Pa]	Δp^r [Pa]	δ [−]	Δp^f [Pa]	Δp^r [Pa]	δ [−]
0	3.49	1.77	1.98	3.49	1.77	1.98
0.1	454	109	4.19	322	36.8	8.75
0.2	905	246	3.74	640	109	5.88
0.3	1,360	530	2.58	959	190	5.05

Figure 5. Penetration of the nanofiber mixed filters, (a) NF-a and (b) NF-b, as a function of particle diameter. The inhomogeneity factor of the fiber packing (δ) was used to calculate the theoretical curves (solid lines).

Figure 6. Calculated quality factor of the NF/MF mixed filter as a function of NF diameter. Dispersion of fiber diameter, σ, and inhomogeneity of the fiber packing, δ, were set to 0 and 1, respectively.

Figure 7. Comparison of the experimental and theoretical quality factor values of the nanofiber mixed filters, (a) NF-a and (b) NF-b, as a function of particle diameter. The inhomogeneity factor of the fiber packing, δ, was set to 1 for the calculations.

Figure 8. Quality factor (Q_f) of the NF/MF mixed filters plotted against inhomogeneity factor of the fiber packing (δ). The broken lines show the theoretical values of Q_f.

Japanese Industrial Standard (JIS) P-8222. 2005. Pulps - Preparation of laboratory sheets for physical testing - Conventional sheet-former method.

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