1) Overview (coming soon)2) Cooling Tank
3) Connectivity (coming soon)
4) Condenser (coming soon)
5) Chilled Water Supply (coming soon)
6) Safety Systems (coming soon)
7) Power Supply (coming soon)2) Cooling tankMaterial considerations.
Fluorinert is a highly inert fluid, it is also a poor solvent with most materials, and it is hydrophobic. These characteristics make it an ideal working fluid. However Fluorinert is an effective solvent for fluorinated compounds (materials containing fluorine), plasticizers, and some additives to soft "plastics".
This presents two challenges (and will be covered more in challenges section). The first it that Fluorinert can replace by volume a portion of the compatible material in gaskets, seals, and orings. For example when silicon adhesive is immersed in FC-72 up to 7% of the volume is replaced with Fluorinert. This can lead to failure of seals in sealants, gaskets and o-rings. Even when they use the same underlying compound "hard" materials are less prone to replacement than "soft" materials (i.e. rigid PVC pipe vs PVC wire insulation).
Material compatibility analysis by CERNhttp://detector-cooling.web.cern.ch/detector-cooling/data/3M_FAQ_Fluorinert.pdfhttp://detector-cooling.web.cern.ch/detector-cooling/data/Fluoro_Compatibility.htm
It is not possible in one post to do an exhaustive analysis of potential material risks so if you are interesting in working with immersion cooling I strongly recommend reviewing both of the links above and conducting your own research. DISCLAIMER: All of this is experimental. Damage to equipment can occur.
If you are unwilling to do self research and testing this type of project may not be realistic. The challenges of material compatibility and handling dissolved contaminants will be covered in the challenges section.Material choices for tank
Glass aquarium can be used for a prototype but due to the use of silicon adhesive below the fluid line I would caution against its use long term. Stainless steel tank is a good option for the ability to design and construct a custom sized tank. To reduce heat conduction a double tank design could be constructed with an inner stainless steel tank surrounded by insulation, surrounded by an outer tank. To reduce costs the outer tank could be constructed from a cheaper material than stainless steel.
For my initial prototype I will be used a polycarbonate NEMA 4 enclosure with the opening facing upward. It would be best in any inlet be through the sidewall of the tank not the lid however in my prototype I will be cutting through the lid as any mistake can be fixed by replacing the lid instead of the more expensive body. Some NEMA 4 enclosures come pre tapped with inlets that are gasketed. That should be avoided for the reasons above instead look for a solid body design.Design of the cooling tank.
The tank should be designed to have no penetrations below the fluid line. The fluid depth should be sufficient to cover all components plus a safety margin of 30mm. In normal operation the fluid in the tank should be relatively constant (<5mm change in depth) however a failure of one or more cooling components will result in the condenser temperature rising and the condenser will be unable to condense (cool) the working fluid as fast as it is being boiled off and the fluid will fall. The safety margin ensures that there is a delay between any failure and the components boiling off their fluid and likely being damaged. To protect the safety margin a depth switch connected to a relay can be used to cut off power to the tank if the fluid level drops. When planning the tank there should be sufficient space in the tank to contain the boiled Fluorinert gas. As a starting point you should plan for no less volume than the volume of the fluid. In addition you should consider the height of the heat exchanger.
As an example the highest component to be cooled is 100mm from the bottom of the tank. The normal fluid depth should then be 130mm. A float switch is installed which will trip and cut all power to the tank if the fluid depth drops below 115mm. You should plan for a gas height at least equal to the fluid height which would be another 130mm. The heat exchanger has a height of 50mm. The tank should have a combined height of at least 310mm. There should be no inlets in the lower 130mm of the tank.
The components to be cooled are submerged in the working fluid, if possible the tank size should be optimized to minimize the amount of working fluid necessary to submerge the components. Due to the high cost of Fluorinert (~$80 per Liter) a design which achieves the minimum amount of fluid to transfer the heat will be more economical. Remember Fluorinert can handle a significant heat load so you can use it sparingly. 3M has shown effective heat transfer with as little as 1L for 4KW of heat load while it is unlikely that you will acheive that level of energy density it shows that excess fluid isn't necessary.
One design consideration is what components will be included in the tank. An SHA-2 hashing system consists of three major components. One or more processors boards, a host/controller, and one or more ATX power supplies. It is possible to use immersion cooling to cool just processor boards or the entire system. There are advantages and disadvantages to both.
Lets consider an example 4TH/s system using HashFast ASIC boards
Processing Boards - 2780W (87%) 
Host - 100W (3%) 
Power Supply (10%) 
Total: 3200W 10 boards @ 400 GH/s nominal, 278W per board
 Low power PC, using a embedded computer like Beagle Board would reduce wattage further
 The wattage is the "lost" power converted to heat. Multiple 90% efficient ATX style 80-Gold or 80-Platinum PSU. Power supply could possibly be in n+1 fault tolerant configuration. In: 3200W AC Out: 2880W DC + 320W heat.
Immersion cooling only processing boards
Highest energy density.
Reduced tank size.
Most efficient use of Fluorinert (highest W/L)
Complicates power delivery. Either custom high current cables are needed or large number of cables need to pass through the tank bulkhead.
Still need to air cool other components.
Potentially prevents deployment to areas where temp outside the tank is ill suited for air cooling (i.e. non-air conditioned warehouse).
Not silent due to PSU fan noise.
If cooling water line bursts the components outside the tank (as well as operators) are vulnerable to being damaged by short circuit conditions.
Immersion cooling all components
Simplified tank connection (can be reduced to: data cable, power cable, water in, and water out lines).
Power supplies may need to be modified. Fans should be removed and power supply fan monitoring bypassed (if present).
Near silent operation (if cooling water heat transfer is in another location).
Larger tank (more significant than may initially appear. remove heatsinks and fans from a hashing board and the power supply has almost the same volume as the boards it will power).
Less efficient use of Fluorinert (lower W/L).
Internal wire management can be more difficult if tank is cramped.
Replacement of failed host or power supply is more complicated.
Depending on the boards used a hybrid between the two options would be to use immersion cooling for the processors and power supplies and place the host/controller outside the tank. For larger operations this may be desirable as a "hot swap" replacement of defective host could be performed easily. This may not be possible with all SHA-2 processors but in at least one case the HashFast boards are connected by USB to any host capable of running cgminer and linux. So data connection to tank could be a single usb port and the host host system be as far from the tank as allowed by USB spec or even one host controlling multiple tanks. The USB cable length can be extended using cheap Cat5/6 cable with an active converter