Dispersion of Expiratory Droplets in a General Hospital Ward with Ceiling Mixing Type Mechanical Ventilation System

Figures & data

FIG. 1 Schematic diagram of the experimental ward and the IMI measurement setup.

TABLE 1 Boundary conditions and parameter inputs for the numerical simulations

Supply air conditions

Total supply airflow rate: 1060m^3/hr (corresponded to 11.6ACH)

Supply diffuser: 4 = way spread type, supply jets had an angle of 15° from ceiling

Turbulence intensity at supply outlet: 45% (obtained from PIV measurement)

Supply air temperature: 294.5 K (21.5°C)

Supply air water vapor mass fraction: 0.00963 (corresponded to 60% RH)

Boundary effects to aerosols

Solid walls: Trap Supply inlet: Reflect     Exhaust outlet: Escape

Droplet injection properties

Air velocity at injection nozzle outlet: 10 m/s     Binary diffusivity of water vapor in air: 0.288 cm^2/s

Air temperature at injection nozzle outlet: 307 K Volatile fraction: 0.94

Material: Water     Airflow rate: 0.4 L/s

TABLE 2 Injection droplet size distribution used in the numerical simulations

		Number	Estimated
Initial size		concentration*	nucleus
[μ m]	Count	[cm^− 3]	size** [μ m]
1.5	500	1.3	0.6
3	2900	7.3	1.5
6	9700	24.3	2.4
12	16000	40.0	4.7
20	8700	21.8	7.8
28	4200	10.5	11.0
36	2400	6.0	14.1
45	1100	2.8	17.6
62.5	1400	3.5	24.5
87.5	850	2.1	34.3
112.5	480	1.2	44.2
137.5	380	1.0	54.0
175	350	0.9	68.5
225	290	0.7	88.1
375	340	0.9	146.8
750	120	0.3	293.6
1500	20	0.1	587.2

FIG. 2 (a) Measured integral length scales at different locations. (b) Measured integral time scales at different locations.

FIG. 3 Schematic of the droplet generator setup.

FIG. 4 Droplet size distribution measured at the droplet generator.

FIG. 5 Grid of measurement positions for droplet dispersion experiments.

FIG. 6 Decay in number fraction of selected size bins of droplets. Legends indicate initial droplet sizes.

FIG. 7 Removal number fractions for selected size bins of droplets.

FIG. 8 Mean vertical positions of selected size bins of droplets. Legends and indicators are initial droplet sizes.

FIG. 9 (a) Mean dispersion distances of selected size bins of droplets in X direction. Legends and indicators are initial droplet sizes. (b) Mean dispersion distances of selected size bins of droplets in Y direction. Legends and indicators are initial droplet sizes.

FIG. 10 Overall dispersion coefficients of selected size bins in the initial dispersion stage.