As all of you know by now my old friend Bob Simons decided to leave the editorial staff of this magazine. Knowing Bob already for many years before he joined the staff in 2000 I was delighted to have him on board. What I always will remember of him are his punctuality, his thorough and elaborate reviews, and his amazing ability to find and correct all kinds of errors in the final proof. And of course his knowledge on almost any kind of topic related to heat transfer. Bob, I will miss you, but I am sure Madhu Iyengar who was no doubt trained by you will fill the gap.
Writing about goodbyes, it is now three years ago that I retired from Philips Research, celebrating this occasion together with my 40 years of work for Philips (which was really an accomplishment for both parties). I was allowed to organize a minisymposium where I invited old friends to talk about developments in their respective fields of interest, and of course say a few nice words about myself: Bob Moffat, Peter Raad, Nabil Sabry, John Parry and my old friend for almost 50 years Jan Dietz, professor in Enterprise Engineering and an expert in the behavior of red, blue and green Gnomes. Fun it was!
Another goodbye that started a sweet memory was what I thought would be my last visit to Semitherm, the forum where I operated for almost 20 years and where I made many friends. When I finished my presentation in 2009, Dave Saums entered the floor and said some very nice things about me as a consequence of which I got a standing ovation from the whole audience. That was touching indeed. But as it turned out, it was not the last time. This year I agreed to present a course on LED system thermal management and I invited Cathy Biber to join me. I used this occasion also to attend the post-conference JEDEC meeting. As you may know I was pretty much involved in IC package thermal standardization for a long time, and at this meeting I made use of the opportunity to start a discussion on LED thermal standardization. Based on all this experience, I happen to have some ideas about the thermal standardization of heat sink performance data, a discussion started by the ASME K16 committee over 15 years ago, unfortunately without jumping to solid conclusions [1]. I decided that it was high time to revitalize this discussion, mainly because the new opportunities that heat sink optimization might provide for the exponentially growing LED business, leading to all kinds of fancy designs that were never seen before and are far away from the ‘standard’ extrusion-dominated shapes. Here are a few thoughts that might be of interest to a larger audience. A starting point is that the designer is faced with the following problem areas:
- Many new developments, in manufacturing as well as in layout (extruded, corrugated, pin fin, metal foam, narrow channel, enhanced plastic, etc.)
- Many choices for optimization criteria (performance, weight, volume, cost)
- Data need to include pressure drop
- Manufacturer’s data are often useless in practice
- Standard correlations fail (usually only valid for parallel-plate confined heat sinks)
- Not having a fan does not mean we talk natural convection at the system level
- Full-blown CFD is often not a solution at the system level
To discuss these issues in some detail exceeds by far the space I am allowed to use in my editorial, but the good news is that a Chapter on heat sink design will appear in an upcoming book on Thermal Management of LED applications. In this Chapter, I will discuss many popular approaches that I do consider unsuitable and three approaches that I do recommend:
- Dedicated tests to rank a series of heat sinks
- CFD with calibrated heat sink compact models
- Smart prototype testing to realize a fast learning curve
In summary: if you want to get the maximum out of your design, heat sink optimization is one way to explore, and don’t trust correlations and vendor data when optimization is your objective!
[1] Belady C., “Standardizing heat sink characterization for forced convection”, ElectronicsCooling, September 1997
Another goodbye
After I finished this editorial I decided to leave the editorial staff myself. In short it boils down to the following: I simply don’t want the responsibility anymore for circumstances that I cannot influence. So, the choice is clear: either the system changes, or I, and I don’t see the system changing on a short notice while I am too old to change. This decision really hurts because I was there right from the start in 1995 and I have always enjoyed the work associated with being an editor very much. Hence, another birth of a memory, but one that includes many thanks to my fellow editors from which I learned a lot over all those years, to Flomerics/Mentor who made the magazine possible, and to the many readers who regularly showed their appreciation for what we were doing.
