Miniature-Portable-Subsonic Wind Tunnel for Aerodynamic and Heat Transfer Measurements Designed for Classroom Demonstration Purposes
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The Miniature Portable Subsonic Wind Tunnel project is a venture by the students in ME414W class to design and construct a portable wind tunnel for classroom demonstrations. This model must be easily transported to and from class, but also large enough for students to see demonstrations. The model must include the capability to display pressure and velocity changes, heat transfer effects, and flow visualization over models. The wind tunnel size specifications were chosen so that the design would yield the requested 10 m/s flow velocity. The test section area is 13 cm by 9 cm, and the 15 VAC, 30-Watt fan in this configuration delivers 355 cfm. The calculated pressure drop across the tunnel is 0.2487 in H20 including a factor of safety. This pressure drop is measured using an inclined manometer, with various pressure taps throughout the tunnel. The air speed is variable through the use of the adjustable speed controller for the output of the fan. A pitot probe was incorporated to measure the velocity of the flow. With the maximum flow rate of 355 cfm, the boundary layer thickness at the exit of the test section was calculated to be 0.16 cm. The wind tunnel incorporates a heating element to demonstrate heat transfer. The heated area is approximately equal to the bottom area of the test section which is 225 cm2. This temperature difference is provided by a silicone runner heat blanket which is controlled by a temperature regulator. The necessary temperature difference of 20 degrees can be achieved, and the multimeter with temperature measurement capabilities can be used to monitor both the surface and ambient temperatures. Demonstrations of flow in the test section are achieved by using a flow visualization technique that incorporates dry ice and various test models. When combined with water, the dry ice emits a vapor that demonstrates the air flow through the tunnel. The flow visualization over the models demonstrates flow separation, drag coefficients, and stalling.
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A subsonic wind tunnel is one of the basic apparatus that is needed for undergraduate fluid mechanics classes. Wind tunnels allow for demonstrations involving air flow, velocity and static pressure measurements, drag and lift measurements, and also reduction of turbulence through the use of screens and honeycombs. Additionally, they can be used to demonstrate heat transfer by heating a side of the test section. A portable and miniature wind tunnel would allow instructors to demonstrate these principles without having to leave the classroom.
The main objective of the project is to design and build a miniature and portable wind tunnel with heat transfer capabilities. The tunnel needs to be large enough for students to see the demonstration, but light and small enough for an instructor to carry to class. It should be easily operated by plugging in to a regular 110 V AC outlet. Pressure measuring devices such as an inclined manometer, Pitot probes, and static pressure taps should be implemented in the design. A flow visualization system and stands to attach test models within the test section are desirable. The test section should be transparent and capable of fitting on an overhead projector so that the flow patterns can be projected on the screen in the classroom. The bottom test surface should have heating capabilities in order to determine the heat transfer coefficient.
A miniature portable wind tunnel capable of heat transfer measurements was designed
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Wind
tunnel dimensions were calculated
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Appropriate materials for the wind tunnel were selected
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A flow
of 10 m/s is needed to overcome pressure drops throughout the wind
tunnel
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Heat
transfer measurements
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Heat
generation
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Flow
models to be used in the test section
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Flow
visualization
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04/18/2005