CPU Cooler Air Conditioner Mk1 – The Test

The last time we were here, I left you with a quick construction that tested a concept that I had had in my head for a few years, but never got around to verifying:  Linking a CPU Cooler to a Heatsink immersed in icy water to transfer the heat in the air into the icy water, blowing cooled air into one’s face.  That was the theory, anyway.

That said, if life has taught me anything, it is that theory and practice are two different things.  It is all well and good for me to claim that the CPU Cooler Air Conditioner Mk.1 works because my theory sounds good and the air seems to be cooler when it leaves the fan, but to really prove this idea, I need to put some numbers to it.  To this end I have obtained a meat thermometer from my local supermarket, which isn’t much compared to a UKAS-certified thermocouple and reader, but it allows readings to one decimal place and should be reasonably accurate.

The Method

The Control

The first thing to do is quite obviously to establish what the Control is, which in this case would be the ambient air temperature.  There is also a dial thermometer mounted on the wall in my room, which I will monitor to gauge whether the ambient temperature is increasing or decreasing during the course of the experiments.

The Fan Test

The next thing to be done is to determine what temperature readings would be obtained with the fan from each system running at full tilt on it’s own.  This will provide what is, in effect, a second control for the system under test, ensuring that we know whether it is the fan doing all the work.  The temperature probe will be raised into the airflow next to the fan for ten minutes, after which the temperature reading will be recorded.

The Ice-Water Test

This is where the systems are put to the test-proper.  Each system will be tested with the same amount of ice (250g, as this is what will fill the cheese-grater tub), immersed in water almost to the top of the container, leaving a gap to allow for melting ice to fill the tub further.  The full setup is then allowed to work for fifteen minutes, after which the temperature of the air leaving the fan is recorded.  After this test is completed, the water will be drained and the remaining ice salvaged for use in the next test.

The Ice-Salt-Water Test

The final test is the same as the Ice-Water test above, but with a controlled amount of salt (50g) stirred into the Ice-Water mixture; this is likely to saturate the water with salt at the temperatures and volumes we are dealing with.  This is to test the theory that adding salt to the water will lower the freezing point of the water, which will permit it to attain a lower temperature and thus chill the air (or the heatsink in the case of the CPU Cooler Air Conditioner Mk.1) to a lower temperature.  After this test the salt-water and ice are both discarded.

The Results

Setup Temperature (℃)
Ambient Air Temperature (Control) 25.8
Silverstone RL4Z S1803212H-3M 180mm Fan 26.1
Zalman CNPS9900 Max 26
Silverstone RL4Z S1803212H-3M + Ice-Water Cheese Grater 26.7
Silverstone RL4Z S1803212H-3M + Ice-Salt-Water Cheese Grater 26.8
CPU Cooler Air Conditioner Mk.1 25.3
CPU Cooler Air Conditioner Mk.1 (Ice-Salt-Water) 25.5

The Verdict:  Inconclusive

There are some conclusions to be drawn from the results beyond the notion that you might as well just blow a fan on yourself:

  • The Air Conditioner does indicate that the concept works, but the low level of cooling suggests that it is inefficient.
  • The Fan + Cheese Grater solution is a complete farce, with it’s results indicating a rise in air temperatures.
  • Adding salt to the water does not increase cooling effects – possibly the opposite is true – and it could be harmful to the unit in the long run with increased risks of corrosion.
Possible improvements:
  1. Add a Peltier plate between the CPU Cooler and the Heatsink to act as a heat pump to force heat energy into the ice water.
  2. Some kind of agitator mechanism to stir the water, to help prevent algae growth and circulate cool water around the heatsink.
  3. As TIM needs a solvent to clean it off of a CPU after use, I doubt that it can be washed away; that said, it would help to create a waterproof barrier around the heatsink on the lid to prevent contamination of the water by the TIM, possibly allowing the water to be drunk after use (once it has cooled down!).

CPU Cooler Air Conditioner Mk1

CPU Cooler Air Conditioner.

Just over a week ago I tweeted a picture of a setup I had going on my PC Desk; Essentially, fill a cheese grating tub with iced salt water (the salt lowers the freezing point of water, hence it’s use on icy roads), put the grating lid on top (leave the tub lid off, but you can use it to prevent spillage whilst moving the unit around) and place it in front of an old PC Fan you have lying around.  You’re going to want as big a fan as possible, as they tend to have both respectable airflow and reasonable noise levels.

The way this worked was that there would be a chamber of air above the iced salt water that would be cooled when air particles hit the water and transferred their heat energy to the water – heat will always travel towards the cold – and the air will thus get colder.  The fan will then pick up this chilly air and thrust it towards the user, while fresh air will be sucked into the tub to be cooled by the iced salt water and thrust forward.

It seemed to work, both in principle and in practice, but it did have some drawbacks:

  1. The cooling effect depends on whether or not the air remains in contact with the water long enough to lose a significant amount of heat energy, if it even contacts the water at all.
  2. The fan was never exactly stable, being unprotected and therefore prone to breakage (of either the fan or my fingers).
  3. As I have learned to my cost, the iced salt water solution is very easy to spill.

So this got me thinking:  Was there a way for me to bypass the need to rely on air – a notoriously poor conductor of heat – in order to transmit the heat from the air to the iced water solution directly?

The CPU Cooler in question

It was at this point that I remembered about the Zalman CNPS9900 MAX that I had recently dispensed with from my Main PC on account of the space it took up inside the now tiny case.  Zalman were famous for their flower-shaped CPU coolers in the Athlon XP/Pentium 4 days when I began in PC Hardware, and this design was their last hurrah, a circular rebuke to the quadrilateral, functional wave of the future that now dominates CPU Cooler design.  Effective, yes, but also incomparably bland, as is now becoming true of most AIO Coolers.

This cooler has been in my possession since 2011 and has outlasted several generations of graphics cards, so I felt it was my duty to give such a long-serving component a new lease of life, even if it suffered the ignominy of being perched upon a lunchbox for the rest of it’s life.

The Build

The Component Parts

Still, a fantastic CPU Cooler is worth nothing without the right kit to enable it to perform it’s job.  In a PC this means a CPU to perch it on, and in this case it means the following items:

Materials required for CPU Cooler Air Conditioner.
From left to right: Lunchbox (with rubber seal to prevent leaking water), CPU Cooler, plain aluminium heatsink (using one with copper or other metals present introduces the risk of electrolytic corrosion), and a set of nuts and bolts. The Aluminium plate was originally intended to bridge the gap between the heatsink and CPU Cooler, but this turned out to be surplus to requirements.

Could hardly be simpler, could it?  The only additional bits used were a couple of compounds; Nut Lock to set the nuts in place, and TIM (Thermal Interface Material) to create an effective heat transfer between the heatsink and CPU Cooler by filling surface imperfections with a conductive paste.

The build commences!

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The whole process was over in a couple of hours.  Not so good for aesthetics, but brilliant for those of us with things to do and places to be.

The End Result

I would say the results spoke for themselves, if this was indeed anything more than a proof-of-concept.  This device looks like the sort of constructions that would scatter around weapons laboratories up and down the country in the next world war.

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So how effective is it?  First impressions indicate a positive result, with the air being blown from the device being noticeably colder than if it were from the CPU Cooler alone.  How does it satisfy the three drawbacks I outlined before?

  1. The cooling effect no longer relies on the rather dubious concept of air being cooled by a chilly body of water in an enclosed space, and then extracted by a fan.  The chilly body of water is now receiving heat energy from the CPU Cooler taking it from the air, transferring it to the lower heatsink, which then conducts it to the water.  In doing this a direct heat path to the icy water is created.
  2. The fan is mounted into the CPU Cooler, which means it is protected by it’s fins.  The Zalman doesn’t have an outer shroud like most CPU Coolers do, so the blade tips are still vulnerable, but it’s a better deal for both your fingers and the fan than simply standing it up on it’s frame.  Most modern CPU Coolers use fans with an outer casing.  There is also the fact that it is mounted to a lunchbox full of water, which prevents it from tipping easily.
  3. The gap for the CPU Cooler and heatsink to mate through isn’t watertight, so spillage is still possible.  The aforementioned stability of the device and the fact that the edges of the lid are sealed, however, does mean that spills are a lot less likely.

So there are many concrete advantages to this configuration.  With regards to it’s effectiveness, however, going by “feel” is no way to ascertain whether a device is functioning correctly.  Join me next week as I obtain a thermometer and put this to the test, also assessing this solution against the old cheese grater solution.