Thermosyphons – The Half Pint Test

SUMMARY: Small 92 mm condenser delivers competitive performance.


One of our test objectives is to see how small we can get the condenser with “acceptable” performance; with micro case sizes taking an increasingly larger share of the market, a compact 92 mm thermosyphon could have some definite advantages. We took a 200 mm condenser, cut it in half and tested it with a single 92 mm fan.


The Thermosyphon shown above (spec’d for 200 watts) was tested on an Acorp 4S845A motherboard with a modified P4 1500 to read CPU case temps. For testing, I used 1 NMB 92 mm fan (#3610K4-04W-B50 vented) spinning at 3298 rpm.

TEST RESULTS – Acorp 4S845A Motherboard

CPU Case Temp

Ambient Temp



MBM Temp

3210 rpm, 61 dBA²






¹MBM on-die temperatures.

This places results in the top rank of P4 air cooled solutions I’ve tested to date (HERE), with the added benefit of a cooling solution that will handle 200 watts.

Another test I ran was using a die simulator with a die measuring one inch square at 69.7 watts. This test resulted in a C/W of 0.14 – similar to the Acorp result.


While not directly comparable to earlier thermosyphon tests (the boiler design is different, among other factors), it is interesting to note that this more compact design does not degrade markedly from a condenser twice as large – roughly a difference of about 0.02 C/W.

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Disclosure: Joe Citarella has a financial interest in a company developing thermosyphon products for electronic chip cooling.