What is “HEV”? HEV stands for “Heatsink Efficiency Value” and is my take on a new value to directly compare dissimilar heatsinks.
The idea for this value came up while trying to test the difference between copper and aluminum heatsinks. While I could get temperature readouts, and C/W, there was no way to tell which material was actually performing better due to the differences in the heatsink sizes.
HEV takes into consideration a heatsink’s surface area in determining its HEV value. (Admittedly though, finding the surface area for some heatsinks can be quite tough, and manufacturers don’t always disclose that information.) Right now HEV is intended for air-cooled solutions, but if anyone cared to calculate the surface area of their water blocks cooling surfaces, HEV should work just fine for water applications.
After using HEV, I realized it has some good potential for comparing the impact of various heatsink designs. It also gives a good direct comparison between two or more heatsinks regardless of their size differences.
HEV takes into consideration the following items:
- Ambient Temperature
- CPU Temperature
- Source Heat (in Watts)
- heatsink Surface Area
HEV DOES NOT take into consideration:
- Fan type/speed
- Exhaust Fan placement/configuration
HEV CAN, however, help you determine how your heatsink stands up to competition. For instance, you can directly compare two copper heatsinks. A difference in HEV will indicate one heatsink is more efficient, probably due to construction, design, etc. During testing, one difference I saw was in construction. For instance, cheaper copper heatsinks with poorly soldered fins would do worse than a skived heatsink of the same material.
Because HEV takes surface area into consideration, you get a relative efficiency value. That means you see how well a heatsink works based on its design, not sheer size. A well designed 1U heatsink may actually be more efficient than a big monster of a sink that is poorly made. Just the same, HEV can be a great tool for testing the efficiency of various materials, construction techniques, or even heat pipe implementation.
HEV can also be a great tool for those looking to experiment with various fan placement methods. Using HEV, you can try fans in push or pull configurations, side mounted, etc, on various heatsinks and compare the results to find the most efficient fan placement. Also, it’s great for finding out which fans work best. As has been said before, CFM doesn’t mean that much. I found that a Delta 38 constantly out-scored an 80mm fan of similar CFM. (And I have the near-deafness to prove it!)
(In fact, the extreme differences in fan design, quality, and air output are why HEV does not factor in fan type – fans are just too varied.)
HEV is a simple value: It’s basically just C/W over Surface Area * 1000 to get a good working value. With HEV, lower is better – just like C/W.
As I said earlier though, finding surface area can be tough. But once you find it, you can learn a lot about your heatsink or various ways of using it. Best way to find surface area, if you can’t find it on the web, is to measure! Any exposed surface will count towards surface area. Then it’s just the sum of the length time width of each surface (If anyone has a better way to estimate it, let me know!)
HEV Calc is a small program I wrote in Java. You’ll see I’m no expert programmer, but the program DOES work. You can download it, check the source code, and try it out. It makes calculating HEV easier once you have the variables.
If you’re looking for accurate HEV results, then you must be aware that HEV does not take into consideration fan type, speed, or placement. It would be best to mount the same fan on each heatsink you test and mount them in the factory intended positions.
Also, use the same test software to load each heatsink and take measurements spread out over 1 hour. You will use both average ambient and CPU temps in the program. You can change heat source watts without disrupting the accuracy, which is nice. (Kinda’ nice if you already have the heatsinks mounted in machines and don’t want to take them off. Just mount the same fan on each and go for it.)
I hope you enjoy HEV and the HEV Calculator program!
P.S. If anyone with more programming skills than myself would like to recode the program in another language, give it a better interface, and make a nice easy to use .exe file, go for it, you have my blessings!
Mike O’Konski aka “Breadfan” in the OC Forums