Airflow Testing Results

2012 February 1

With the arrival of the pitot tube and manometer, we were ready to begin taking measurement for our airflow tests. We first mounted the manometer securely to the prototype. It uses a column of fluid as the indicator, so being completely level is important. Once, balanced, the red indicator fluid was added and we attached the pressure sensing lines.

The pitot tube was put into the stream of air flowing out of the duct. In actual operation, the duct would be feeding hot air into the roasting bowl, which is the primary method of transferring heat (convection).

We then moved the pitot tube to various points in the duct to plot the air speed. It is not uniform across the outlet of the duct, which is important to understand. We also throttled the amount of air to see how the beans reacted to increasing air flow.

The pressure difference from the pitot tube translates into movement of the red fluid in the manometer. The tube is scaled to convert the differential pressure into an equivalent air speed in feet per second.

We plotted the airspeed at various points in the duct out let. It averaged 2,600 feet per minute, which is equal to 30 mph. The airflow is then calculated to be 950 CFM.

We have now completed our initial work in proving the concept using the prototype. It is now time to move into building!


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