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Parts List for the Sudden Expansion Exercise

The following list of parts are provided as an aid to instructors wanting to build the sudden expansion device. Specific brands and vendors are provided, but are not meant as an endorsement.

Blower

The first two versions of the sudden expansion used a (now obsolete), two-speed blower from Dayton (4C566). We are currently (Aug 2009) building a third version using a higher capacity, single speed Dayton blower (1TDD5). We ordered the blowers from Grainger.

Positioning Stage

There are many options. We found the A2509Q2-2.5 from Velmex to be relatively inexpensive ($425 in 2007) and to meet our technical requirements (manual, 15cm range of motion, easy-to-read scale).

Velocity Sensor

We considered a pitot tube, but the air velocity range is so low, especially near the duct wall, that the pressure reading would be difficult, if not impractical, to make. Instead we choose a thermal anemometer that is typically used in the HVAC industry. The TSI 8455-12 from TSI cost $730 in 2007.

Pressure Transducer

The pressure differences are quite small, on the order of 0.1 inch of H20. We've had good luck with the PX653 style of transducer sold by Omega. The PX653-0.5D5V was $495 in August 2009.

Data Acquisition

The velocity sensor and pressure transducer both produce signals in the 5V DC range. This is a good match for the National instruments USB-6008.

Acrylic sheet stock and tubes

Available at plastic suppliers, e.g. TAP plastic, or at general parts suppliers like McMaster Carr. There are many suppliers of acrylic sheet and acrylic tubing.

Blast Gate

We found a 6 inch plastic blast gate at a well stocked, independent local hardware store. You can find them for less than $10 at woodworking supply stores, and other retailers. A web search reveals more options. Some woodworkers make their own. Note that metal blast gates are also sold, but these are more expensive and heavy than you need.

Wood

A 8 foot long 2x12 is used to create a base and cradles for the round acrylic sections.

The blower box is made from plywood. 1/2 thick plywood is sufficient.

Miscellaneous

Barbed pressure taps from Dwyer, a hose fitting supplier or a local hardware store.

Vinyl tubing from a local hardware store. Use this to connect the pressure taps to the transducer.

Bulk plastic furnace filter material used to provide some damping upstream of the blast gate. We have not tested whether this makes a difference, but

DC Power Supply: 0 to 12 V. We have a stock of low cost triple outlet supplies (Tenma 72-6628 DC), which are overkill for this project, but can be used on other projects.

Electrical wiring

Deck screws for assembling the blower box

Screening to block fingers and debris from the outlet of the blower.

Thick (3/8 inch or more) foam weather stripping tape is useful to add cushion to accommodate tolerances on the vertical supports for the duct. We also find that a strip of weather strip tape around the perimeter of the tip of the inlet duct will stop the air from whistling. It also makes for interesting conversation with students -- why would the tape stop the whistling?