HECA Air Flow Studies Unit

The Air Flow Studies Unit, "HECA", is a floor standing unit that allows to measure different characteristics of air distribution systems and to demonstrate certain basic principles of fluid mechanics in ducts and jets.

The unit is mounted on a metal frame with wheels and consists of two modules connected one to each other.

One module includes an electrical centrifugal fan, with speed control.

The other module includes a long and smooth test pipe that is connected to the suction side of the centrifugal fan. A deflector in the inlet prevents air separation from the wall of the pipe and reduce the formation of vortices, and the pipe diameter minimizes the presence of turbulence. Several pressure tappings are included along the length of the pipe to determine the pipe friction factor, pressure losses and velocity profiles.

The unit has two Pitot tubes:

• One located at the discharge of the fan, attached and properly protected. It can be situated at different distances from the discharge orifice to study free jet velocity profiles.
• The other one can be located in any of the different points of the test tube to perform an air flow analysis of the velocity profile inside the pipe section. This Pitot tube can also be located at different distances in the pipe to demonstrate the boundary layer growth.

The air flow rate can be measured with various measuring devices, such as iris diaphragm, a Pitot tube, an orifice plate and two nozzles with different diameters.

The unit includes two bends and an angle to fit to the pipe for comparison of pressure losses.

The measuring devices and the Pitot tubes are connected via tubes to a multi-tube inclinable manometer where the pressure differences can be measured. This manometer can be inclined to increase its resolution and can be locked into different positions.