Objective

Verify the lumped capacitance approximation by measuring cylinder cooling time under forced convection in a wind tunnel; find correlation for which material properties influence time-to-cool under lumped capacitance model.

Outcome

The volumetric heat capacity (density multiplied by specific heat) was proven to be the driving factor of cooling time in lumped capacitance and exhibited a far greater correlation than thermal conductivity. 

Findings

This transient heat transfer analysis included nine different cylinder materials and two cylinder diameters; each was placed into a wind tunnel at 40 degrees Celsius and timed until cooled to a temperature of 32 degrees. The average freestream temperature was noted, and the Biot numbers were calculated to ensure that every cylinder complied to the lumped capacitance approximation. The heat transfer coefficient and thermal time constant additionally calculated from the experimental values.