Miniature Pipe Bundle Heat Exchanger for Thermophoretic Deposition of Ultrafine Soot Aerosol Particles at High Flow Velocities

Figures & data

FIG. 1 Cross-sectional area of the miniature pipe bundle heat exchanger. Pipe inner diameter d _i = 0.99 mm, outer diameter d _o = 1.59 mm. Aerosol flow around the cooling tubes flown through by cooling air.

FIG. 2 Photograph of the pipe bundle heat exchanger inlet section.

FIG. 3 Longitudinal section of the pipe bundle heat exchanger. Note the symmetrical design of the deposition device.

FIG. 4 Schematic flow diagram of the experimental setup for counterflow heat exchanger particle deposition measurements.

TABLE 1 Experimental parameters for the investigation of the particle deposition mechanisms in the miniature pipe bundle heat exchanger

Exp.	V h,out [l min^−1]	v x,hot,in [m s^−1]	T h,in [K]	T h,out [K]	T c,in [K]	T c,out [K]	ΔT log,mean [K]	Re	V c,in [l min^−1]
I a	3	1.31	403.5	301.9	300.5	329.5	18.30	64.8	5
I b	3	1.41	436.0	302.8	301.0	338.8	23.92	63.1	5
I c	3	1.49	460.5	303.5	301.4	346.5	28.02	62.0	5
I d	3	1.58	489.0	304.1	301.5	356.0	33.14	60.8	5
II a	4	1.73	400.2	301.1	300.0	333.1	16.04	86.7	5
II b	4	1.79	414.0	303.5	299.5	342.5	23.40	85.4	5
II c	4	2.05	474.8	303.3	300.1	363.2	30.60	81.8	5
II d	4	2.16	499.0	300.4	297.8	373.0	32.80	81.0	5
III a	5	2.17	401.5	301.3	300.5	330.4	15.64	108.2	10
III b	5	2.37	440.1	301.6	300.7	341.0	20.87	105.0	10
III c	5	2.55	473.0	302.8	301.7	352.5	25.42	102.5	10
III d	5	2.74	507.9	304.4	303.0	364.5	30.69	100.1	10
IV a	6	2.55	393.5	302.4	297.6	344.7	18.97	130.5	5
IV b	6	2.64	407.3	303.7	302.3	339.8	17.06	128.8	10
IV c	6	2.86	442.5	304.9	303.2	352.1	22.32	125.2	10
IV d	6	3.03	468.0	300.8	298.9	359.0	26.45	123.8	10
IV e	6	3.2	494.7	301.0	299.3	367.1	29.23	121.6	10
V a	8	3.35	387.5	302.3	300.3	339.9	14.36	174.9	10
V b	8	3.86	447.0	303.8	300.7	366.5	23.77	166.7	10
V c	8	4.16	482.1	304.0	300.2	381.0	29.63	162.8	10
Volumetric flow rates at ambient temperature and pressure: 300 K, 950 mbar

FIG. 5 Soot-particle size distributions measured before and after the heat exchanger in experiment Ia (arithmetic mean ± standard deviation of 6 measurements each).

FIG. 6 Total particle deposition efficiencies ϵ_tot,i and isothermal losses ϵ_iso,i in the pipe bundle heat exchanger for experiments Ia–Id. Data points with error bars represent the arithmetic mean ± standard deviation of 11 differential measurement values.

FIG. 7 Total particle deposition efficiencies ϵ_tot,i , isothermal losses ϵ_iso,i , and thermophoretic deposition efficiencies ϵ_th,i calculated with f(iso,th) = −ϵ_th,i · ϵ_iso,I and f(iso,th) = 0, respectively, for experiment Ia. Data points with error bars represent the arithmetic mean ± standard deviation of 11 differential measurement values; dashed line illustrates ϵ_th,avg calculated with f(iso,th) = −ϵ_th,i · ϵ_iso,i .

FIG. 8 Total particle deposition efficiency ϵ_tot,avg plotted against the dimensionless precipitator number calculated from average flow parameters, (Lμ₀Δ T _log,mean)/(v ₀ρ₀ T ₀ H _ch ²). The lines are linear least-squares fits to the data sets with different cooling air flow rates (5 l min^{− 1} dotted; 10 l min^{− 1} dashed). Error bars represent the standard deviation (±1 s.d.) of the averaged values ϵ_tot,i .

FIG. 9 Thermophoretic particle deposition efficiency ϵ_th,avg plotted against the dimensionless precipitator number calculated from average flow parameters, (Lμ₀Δ T _log,mean)/(v ₀ρ₀ T ₀ H _ch ²). The lines are linear least-squares fits to the data sets with different cooling air flow rates (5 l min^{− 1} dotted; 10 l min^{− 1} dashed) and the theoretical relation for a plate precipitator (solid). Error bars represent the standard deviation (±1 s.d.) of the averaged values ϵ_th,i .

FIG. 10 Thermophoretic particle deposition efficiency ϵ_th,i plotted against the dimensionless precipitator number calculated from effective flow parameters at the hot inlet, (L ^*μ _h,inΔ T _h,in)/(v _h,inρ _h,in T _h,in H _ch ²). The line is the theoretical relation for a plate precipitator. Error bars represent the standard deviation (±1 s.d.) of the averaged values ϵ_th,i .