As I noted in our last post, you’d like to think any old heat sink can substitute for any old other heat sink?  Just get the right size and thunk it down, blow enough air on it and your good to go. Well, as we noted in our last post, “The Fallacy of the Drop-In Replacement Heat Sink“, it’s not that simple. In fact, there are a wide number of vectors effecting how effective a heat sink and the overall cooling solution is. One of those factors is air velocity.
ATS Labs took three kinds of heat sinks and put them through their paces in our labs here in Norwood, MA to study this topic. We used a straight fin, a pin fin and, (of course) our patented maxiFLOWTM heat sink.  Our testing involved:
- Drilling holes in the heat sink centers for a thermocouple
- Placing the heat sinks in a wind tunnel on a heater pad
- Taking datapoints at steady state air flow
Here’s a photo of our test setup:
Here’s a descriptive diagram:
The thermal resistance results were very interesting and I’ll just summarize them here.
- maxiFLOWTM Heat Sinks had the lowest thermal resistance
- Straight fin type heat sinks came in second
- Pin fin were third best of the lot
The results were somewhat predictable, though not a slam dunk, given maxiFLOW’sTM design.  The data and table information itself though are invaluable in helping all of us in the thermal design world understand the effect of air velocity on heat sinks. Just one of the many vectors of design for the right solution. You may download and read the entire study for yourself here, “How does air velocity effect the thermal performance of heat sinks?“