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Bubble Rocks
Bubble Rocks, a two phase liquid immersion cooled computer.
Bubblerocks front
Bubblerocks back
Overview
There are four main ways to cool computers:
- Fan cooling.
- Direct to chip cooling.
- Single phase immersion cooling.
- Two phase immersion cooling.
Design
Two phase immersion cooling is the most efficient. With it a computer is immersed in a liquid like 3M Novec. Novec boils at around 50C, so the heat from the CPU/GPU boils the Novec. When boiling there is a phase change that converts the Novec liquid into a gas. The gas rises to the top of the sealed container, cools at the top, then "rains" back down.
The problem with Novec, is that it has a huge Global Warming Potential, is $5,000 USD per gallon, and is toxic.
This is an idea to do two phase immersion cooling. Is instead of using Novec, use pure water. The electronics are first sealed in an encapsulant material (electronics potting) to protect them from the water. The encapsulant has high thermal conductivity, so it transfers heat. The encapsulant seals out water.
The electronics in the encapsulant are then placed in water. The water is inside a vacuum chamber. The vacuum chamber's pressure is lowered so water will boil at 50C. Then when the electronics get hot, they boil the water to cool them off. Similar to Novec, but in a vacuum and non-toxic.
This is for enterprise hardware, not consumer electronics.
Assuming good vacuum chamber equipment, there should be minimal leaks, if any partly due to the fact that an extreme vacuum isn't needed. This level of a vacuum is easily obtainable by readily available vacuum chambers and pumps.
The encapsulant is CoolTherm SC-324 from Parker Lord. It has 4.0 W/m°K rating. It has Dielectric Strength of 7 kV/mm. It has a shore hardness of 50A.
Add conformal coating to electronics before encapsulant. Add copper heatsinks to CPU/GPU before encapsulant. Apply parylene conformal coating first for moisture barrier. Encapsulant thickness: Minimize to 2-3mm maximum to reduce thermal resistance. Thermal vias: embedded copper particles in encapsulant for better conduction. Embedded copper particles in the encapsulant create thermal vias, improving conduction paths and reducing overall thermal resistance. Copper heatsinks larger that go through the encapsulants and touch the water directly. Or aluminum heatsinks instead.
Vacuum pumps will be oil free and use a cold trap. Stainless steel chamber with proper sealing (O-rings, metal gaskets).
Deionized water to prevent mineral deposits and corrosion.
License
Apache 2.0 license.
Copyright © 2024, 2025 Jeff Moe.