KCR Software HEATSINK is a thermal analysis routine used to estimate the temperature of a finned heatsink under natural convection air flows. Basic configuration data in inputted by the user to define fin geometry, plate orientation, and ambient conditions. Air flow rate are estimated based on buoyancy forces, friction forces, and plate orientation. Heat transfer coefficients, fin efficiency, and plate temperature are determined from air flow rates.

Heat radiates from the base plate and from each fin. The Effective Shape Factor depends on the view factor of each fin with respect to each adjacent fin. In our heatsink routine, emissivity is specified by the user then weighed by the effective fin area and shape factor to calculate an overall radiation heat transfer. Since heatsinks are fabricated of high conductive materials, the fins tend to emit more energy at oblique angles than in a direction normal to the surface. Consequently, shape factors have been weighed with a sinusoidal function to approximate the characteristic.

Fin geometry is used to determine a minimum heat transfer coefficient based on Limiting Nusselt Number. Buoyancy forces are balanced against friction forces in a iterative technique to determine actual air velocity. Colburn number and friction coefficient are determined and an air velocity established for each iteration. A mass flow rate is also determined based on Grashof Number. The heat transfer coefficient between the top of the fin and the boundary layer is based on laminar flow. Heat transfer between the fin and boundary layer is calculated using forced convection heat transfers coefficients. This higher number (h) is required due to some mixing between the fluids.

After the air flows have been determined, all coefficients for our finite difference routine are known and the temperature analysis is performed by HEATSINK writing a heat flow equation for each node and solving these equations simultaneously. The resulting temperatures are now used to calculate new buoyancy forces. This procedure is repeated until new temperatures match old temperatures. On micro computers, the whole calculation procedure only takes milliseconds. We wish to thank Lockheed Electronics Corp. in Plainfield, New Jersey for their generosity in providing test data to verify computer results.

Our software routines may be downloaded from this web site and are fully operational for your testing for about 30 days.