1. High-Power GPU Rack: Hybrid Cooling
11/29/2018

2. Rear Door Heat Exchanger
Side View
Front View
Overview
Rack
Rear Door Heat Exchanger
Does hybrid cooling make sense for a dense / hypothetical GPU rack?
Rack power ~34kW
GPU chassis (JBOG) power ~4kW (qty: 8)
8x 450W each (liquid-cooled; 2x GPUs in series only)
~225W of ancillary power (air-cooled)
Proportion of rack power by cooling
Air-cooled: ~4.5kW (16%)
Liquid-cooled: ~28.5kW (84%)
Liquid returning to cold plates cooled by RDHx
Caveat(s)
CDU not shown here; ~4U space required
Analysis meant to highlight capability only

3. Connections between manifolds, RDHx and CDU
RDHx mounted to rack
Loop Connections
Cold plate  Hot manifold  RDHx  CDU  Cold Manifold  Cold plate…
GPU chassis with open-loop cold plates
Connections between manifolds, RDHx and CDU

4. Rear Door Heat Exchanger
Rack
Rear Door Heat Exchanger
Side View
Functioning
Operating assumptions
Rack power ~34kW
Air-cooled: ~4.5kW (16%)
Liquid-cooled: ~28.5kW (84%)
Airflow through RDHx / rack: 3000CFM
Inlet air to rack: 35°C; sea-level
Approach temperature of RDHx ~13°C
Air
35°C
Air
55°C
5°C
12°C
51°C
Preheat ~3°C
Operating Margins on GPUs