HEAT TRANSPORT FROM A HORIZONTAL PLATE

ILLUSTRATE DIFFERENCES BETWEEN CONVECTION, CONDUCTION AND RADIATION

This system uses a thermocouple sensor to show T(t) above and blow a hot plate.  Alternatively an IR camera can be used to show that one gets convective transport above and radiation or conduction transport below.

 

Setup with thermocouple sensor attached to a hand-held display (lower left).  Alternatively, and better, attach the output of the thermocouple module to the Demonstration Computer Interface, and run the T(t) plot program.

  1. Setup the connection.  Leave heater unplugged.  Test imaging or thermal reading by blowing on the sensor...
  2. Plug the heater film directly into a wall socket.
  3. Wait a few minutes.  Test the plate temperature by touching it.  When it gets too hot to touch UNPLUG.  (Hotter = better visualizations, but too hot = film heater peels off and bubbles.  DO NOT LEAVE CONNECTED WHILE UNATTENDED.
  4. Scan the thermocouple around to see plumes (above) or quasi-steady IR or conductive heating in the thermal boundary layer below the plate.

VISUALIZE WITH IR CAMERA:   Use the IR camera to look for convection above and quasi-stabel thermal boundary layers below.  Show that can't see convection in are because air is transparent or a poor emitter of IR.  Spray the top of the plate (and / or below) with water drop spray to cause water vapor to be convected - this CAN be seen by the IR camera.

QT Movie of Thermal Plumes  (not available yet).


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2000.  John Hart, University of Colorado