Describes different liquid cooling technologies

1. In-Rack CDUs are small, can be integrated directly into a single server chassis, and distribute
coolant to a series of servers or other heat sources.
In-Row CDUs are larger, freestanding, and designed to manage higher heat loads across a series
of server chassis.
CDU
In-Row vs In-Rack

2. CDU Manifolds Cold plates
Connected through
hose/pipes &
connectors
Connected through
Quick disconnects,
hose/pipes &
connectors &
cooling loops
They must be
designed to match
the chip’s
geometry and to
optimize thermal
transfer
efficiency
CDUs are the heart
of a single phased
liquid cooling
solution.
Manifolds help in
distribution
CDU
Manifold
Inside the Rack
Cold plates
Cooling loops
Quick disconnects
Single Phased liquid Cooling (In-
Rack)
Connectors – Used to
connect different
equipment mentioned
above together; Helps
prevents leakage

3. Two-Phased liquid Cooling (In-
Rack)
Couldn’t find much info here. Looks like there is the need of a
condenser which converts the vapor back into liquid before being sent to
CDU’s secondary loop (to get cooled).
Different kind of cold plates required?

4. Immersion Tanks
CDU (in
larger data
centers)
If no CDU, then a
heat exchanger of
some sort needed
to remove the heat
from the coolant
Single Phased Immersion Cooling
Dielectric
coolant
Checked Liquidstack, a firm which started as an immersion
only cooling player – they sell only immersion tanks
(have recently started selling CDUs)
Cooling
Towers/Chilled
Water loop
The immersion tank contains a CDU (coolant distribution
unit) comprising a pump and a plate heat exchanger. The
pump circulates the dielectric fluid within the tank,
extracting heat from the servers. The heated dielectric
fluid then passes through the plate heat exchanger, where
it is cooled by water. Source: Submer
Note: There are some one-phase immersion systems with heat exchangers
located inside of a specially engineered IT chassis, which reduces the need for
a CDU. Source: LiquidStack

5. Immersion Tanks
Two Phased Immersion Cooling
Dielectric
coolant
An example where you don’t need CDUs
Condenser on the
top of immersion
tanks -
(evaporative
coils)
Source:
GreenRevolution
Cooling
Big difference in single phased
immersion & two-phased immersion
is the type of coolant. Two-
phased requires a much more
expensive coolant.