HVAC Mechanical Ventilation
Mechanical ventilation differs from natural ventilation mainly in that the air circulation is performed by mechanical means (such as fans or blowers). In natural ventilation, the air is caused to move by natural forces. In mechanical ventilation, the required air changes are affected partly by diffusion, but chiefly by positive currents put in motion by electrically operated fans or blowers, as shown in Fig. 3-5. Fresh air is usually circulated through registers connected with the outside and warmed as it passes over and through the intervening radiators.