Artificial and Vacuum Ventilation
"Ventilation is a science, and it requires the study of a lifetime to master properly all its Intricacies. The greatest engineering skill is necessary in the arrangement of tubes and the supply of fresh air."
Parkes
Artificial Ventilation.
In the case of large floor areas, such as we have in designs for theatres, factories, large public halls, and other similar buildings, it is necessary to resort to artificial ventilation, which may be tabulated as follows:
· Vacuum or exhaust ventilating schemes.
· Plenum or propulsion ventilating schemes.
· Some combi nation of the above systems.
Vacuum Ventilation.
This is a system of ventilation whereby the internal air is extractedby suitable fans. The ingoing air is inducedthrough windows and other similar inlets already described for natural ventilation, and a steady flow of air is maintainedby means of the extractionfans.
Various types of fans may be used. They are generally made of metal of a rotarydesign and housed in a convenient part of the ductwork. Care must be taken to see that the ductsare ’ fairly straight, and with easy bends if necessary. Avoid righ angled bends,which impairthe efficiency of the system owing to friction.
Fans are usually driven by electric motors, but other power may be utilizedwhere
electricity is not available. With the vacuum ventilating system there is no control of the incoming air; therefore this system can only be employed successfully where the surroundings are not noisy and windows can be opened to admit clear air.
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8. It is necessary to to artificial ventilation in theatres, factories, large public
halls, and other similar buildings.
4. is a system of ventilation whereby the internal air is extracted by suitable fans.
6. The air is induced through windows and other similar inlets already described for natural ventilation.
7. Fans are generally made of of a rotary design and housed in a convenient part of the .
8. Care must be taken to see that the ducts are.
d) are usually driven by electric motors.
d) With the vacuum ventilating system there is no control of the air.
Plenum ventilation.
Control' over the incoming air is an important feature of this type of| ventilation.
Where the conditions are such that the surroundings are noisy and the air is fouled by smoke and dust, the plenum system can be contemplated to provide clean air at the correct temperature and humidity. The drawn into the building by a fan, and is discharged through (it suitable positions; conveniently place the ventilation air through ducts controlled by an extra fan of smaller power than the inlet fan. A slight pressure is created owing large rate. The plenum .system of ventilation is costly to install, owing to the necessity for expensive apparatus consisting of propulsion and extraction fans, air heaters, washers and biters (these vary according to circumstances), and distributing ductwork for the incoming air.
A typical arrangement of plenum heating: The air coming in is heated, by a heater battery, fed from an independent boiler feeding wrought-iron gilled tubes which have a good radiating surface. In summer, however, the alt can be cooled by passing through the same battery fed by an ammonia refrigerating plant. Supplying cold water instead of hot water from the boiler. The ductwork is liable to conve> sound unless special care is taken with, the placing of the fans.
With the vacuum ventilating system there is no control to incoming air; therefore this system can only be employed successfully where the surroundings are not noisy and windows can be opened to admit clean air.
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