Figure 1
The clean-air operating room enclosure at Wrightington Hospital.
Note: 1 = Primary air filter; 2 = fan (two speed 2000 and 4000 ft3/min; 3 = water spray humidifier; 4 = steam heating coil; 5 = motorised steam valve; 6 = motorised spray control; 7 = final filter pockets; 8 = clean air chamber; 9 = UV lights; 10 = temperature probe; 11 = anemometer; 12 = diffuser vanes; 13 = glass enclosure walls; 14 = lights; 15 = suction manifolds; 16 = main suction line; 17 = positive displacement air pump (70 ft3/min); and 18 = wall control panel.
Source: Charnley (1968), provided by Andrew Thomas, Institute of Clinical Sciences, Birmingham. Explanatory sketch: John Charnley.
Figure 2
Results of an experiment to monitor the air mixing in an operating theatre in the Royal Papworth Hospital, Cambridge.
Note: (a) Normalised results of the CO2 measurements, with (b, c) a plan of the location of the sensors and the theatre; and (d) the air flow pattern as interpreted from the measurements of CO2.
Figure 3
Water bath model simulation showing turbulent mixing arising from a precooled downward airflow (pink), and the Ultra Clean Ventilation (UCV) configuration, encountering plumes of heat deriving from surgical staff, the patient and medical machinery (yellow). The clean downflow mixes with the plumes in the operating zone and the air then spreads laterally across the theatre prior to ventilation.
Figure 4
Water bath simulation of warm contaminant (left) entraining within a pre-cooled downflow (right) and descending towards the operating zone.
Note: a time sequence video showing the water bath simulation can be viewed on: https://vimeo.com/710247536
Figure 5
Comparison of (a) upflow displacement ventilation and (b) mixing ventilation produced by the laminar downdraft flow (LDF) of the Ultra Clean Ventilation (UCV) theatre type.
Figure 6
(a) Upflow displacement ventilation with inflow from the two side walls; (b) mixing ventilation; and (c) variance of the dye concentration in the experimental model of mixing laminar downward-flow (LDF) ventilation, relative to the mean concentration, as a function of time, and variation of the log (C(t)/C(0)) as a function of time illustrating that both the contaminants in the ventilation air and those produced by a localised plume in the space decay according to the well-mixed model.
Figure 7
Volume flux in a plume produced by a source of heating as a function of heating rate.
Note: Flux at heights of 2 m (blue line) and 4 m (orange line) above the heat source.
Figure 8
Natural ventilation flow in the surgical theatre, with buoyancy and wind forcing of 0, 10 and 20 Pa, with an area of ducting of 3 m2.
Figure 9
Flow rate as a function of the external temperature, with a wind draw of 10 Pa in addition to buoyancy. Curves are shown for duct areas of 1, 2, 3, 4 and 5 m2.
Figure 10
Operationshaus, St. Georg, Hamburg, 1897: (a) cross-section through the three-dimensional (3D) model; and (b) plan view through the 3D model at eaves height.
Note: 1 = Underfloor heating; 2 = glazing translucent matte; 3 = air cavity; 4 = outer glazing; 5 = air cavity roof; 6 = operable roof panels; 7 = exhaust (cool air return); 8 = fresh air supply; 9 = radiator; and 10 = cooled air back into underfloor heating.
Source: Woods et al. (2021).
Figure 11
Upward flow displacement ventilated space for surgery: (a) aerial view of the new operating theatre model; (b) lateral section of the operating theatre model; and (c) close-up view of the ventilation shaft.
Note: 1 = General room air intake; 2 = general room air supply at a lower level; 3 = glass hood containing exhausted high-efficiency particle arrestor (HEPA)-filtered air; 4 = HEPA-filtered air-focused supply steered by the surgical team; 5 = exhaust for the surgical area into the base of the exhaust stack; 6 = general room exhaust; 7 = surgical area exhaust; 8 = general room air exhaust; 9 = high-level double-glazing and 900 mm ventilated void with a photochromatic glass pane to provide blackout as required; 10 = fixed and seamless glazing contiguous with a solid wall lining; 11 = floor finish with a seamless rubber sheet; 12 = seamless glass panels with a variable colour display; and 13 = vertical sun shading to and east and west sides.
Figure 12
Visualisation of the ventilated environment of the novel upward flow-displacement ventilation surgical theatre. The analogue model fluid flows are superimposed onto the three-dimensional (3D) model used for the animation.