University of Minnesota
University of Minnesota: Department of Mechanical Engineering
http://www.me.umn.edu/

ME 4331: Fin I

Fin Heat Transfer; Fins Part I

Reading: Before you begin this series of tests, read an introductory chapter on fins (may be called "extended surfaces") in an undergraduate heat transfer text.

Objective:

You will investigate the heat transfer characteristics of a rectangular-fin array in a forced-convection environment. The primary goals of the investigation include:

  1. To compare ther performance of a single fin to theoretical predictions of the axial temperature distribution and heat flux; and
  2. To examine the Nusselt-Reynolds number relationship for flat plate flow over the fin.

Experimental Facility:

Heat transfer from an array of extended surfaces will be studied in a forces convective environment provided by a suction type wind tunnel in the laboratory. An array of fins separated by "spacers" will be fixed to an aluminum heating block that is heated by two embedded cartridge heaters. Each heater can dissipate up to 100 W. With the exception of the surface of the block, which is in contact wih the fin array, the heating unit is insulated on all sides by gypsum board. This insulation is assumed to direct all the heat transfer into the fin array; the validity of this assumption must be explored during the course of the study.

The fins and spacers that comprise the array are machined from 6061-T6 alloy aluminum having a thermal conductivity k of 155.8 W/m-K. The central fin in this array is instrumented with seven thermocouples positioned along the axis of the fin, and covering the distance from base to tip. The entire array is mounted in the wind tunnel to facilitate good thermal contact between the array and the heater, and to expose the fins to a nearly uniform approaching air flow having a velocity given by Uf, which can be measured with a total pressure tube and can be varied between approximately 5 and 30 m/sec. by control of the tunnel.

NOTE: The discussion above is intended only to provide a brief background of what you can expect in the laboratory. It is the responsibility of each group to examine the set up and provide sketches of the facilities and hardware.

Recommended Procedure:

  1. To evaluate the fin performance over a wide range of conditions, tests should be conducted in the wind tunnel at 8-10 different velocities. The usable range of the wind tunnel corresponds to frequency settings on the speed controller between 5 Hz and 30 Hz, so select roughly equal intervals in fan frequency over this range.
  2. Under steady state conditions, record the temperature distribution along the length of the fin.
  3. After a data set has been acquired at one operating speed, a new velocity should be selected and the procedure repeated until the fan frequency range has been covered.