Door Heat Exchanger Sub-Project Updates (OCP EMEA Summit 2025)
Open Compute Project Foundation · Jabari George, Martin Doerrich
An update from the OCP Cooling Environments door heat exchanger sub-project on its scope and three active workstreams; a roadmap rather than a specification.
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Overview
This update by Jabari George and Martin Doerrich, presented in the Liquid Cooling track of the OCP EMEA Summit 2025 in Dublin, describes the scope and three active workstreams of the OCP Cooling Environments door heat exchanger sub-project. The scope covers operating conditions, metrology of heat-extraction performance, rack-architecture specifics (Open Rack, EIA-310) and solutions for sites with and without facility water.
There are three workstreams. The first is flow control in technology cooling system (TCS) loops: control valves at header and nodes, pump-based pressure regulation downstream of the CDU, and telemetry-driven optimisation are compared. The second is air-assisted liquid cooling (AALC) with sidecar heat exchangers; sidecar units are said to achieve lower supply-air temperatures than rear-door units thanks to larger coil area, especially at small approach temperature differences. The third is replacing copper with aluminium in rear-door and sidecar coils.
The sidecar workstream defines common terminology and form-factor and redundancy expectations: Single Rack Space units aligned with ORv3 dimensions, with pumps and fans redundant and hot-swappable and the heat exchanger treated as a single point of failure. Aluminium heat exchangers offer cost and weight savings with comparable thermal performance but need coatings and standards-based corrosion mitigation. As a limit, the material is a roadmap rather than a specification, but it frames the parameters designers should specify.
Key points
- Scope covers operating conditions, metrology of heat-extraction performance, rack-architecture specifics (Open Rack, EIA-310) and solutions for sites with and without facility water.
- TCS flow control methods compared: control valves at header and nodes, pump-based pressure regulation downstream of the CDU, and telemetry-driven optimisation.
- Sidecar AALC units can achieve lower supply-air temperatures than rear-door HX thanks to larger coil area, especially at small approach temperature differences.
- Sidecars should align with ORv3 dimensions using Single Rack Space units; pumps and fans redundant and hot-swappable, heat exchanger treated as a single point of failure.
- Aluminium heat exchangers offer cost and weight savings with comparable thermal performance but need coatings and standards-based corrosion mitigation.
Using it in design
- Record approach temperature difference, P-Q curve, fan/pump redundancy and coil material in rear-door and sidecar catalogue items.
- Warn when an aluminium coil is placed on a loop with copper wetted parts without a stated inhibitor strategy.
- Evaluate air-assisted liquid cooling as an option for sites without facility water.
- Treat the heat exchanger in a sidecar as a single point of failure when setting redundancy requirements.
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Who should read it
Cooling engineers selecting rear-door and sidecar heat exchangers and designing liquid loops for Open Rack environments, and manufacturers.
Related standards
- OCP Open Rack V3
Publication details
- Authors
- Jabari George; Martin Doerrich
- Publisher
- Open Compute Project Foundation
- Year
- 2025
- Document number
- OCP EMEA Summit 2025, Liquid Cooling track
- Event
- OCP EMEA Summit 2025, Dublin
- Document language
- English
- Source type
- Industry body
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Citation
Jabari George; Martin Doerrich (2025). Door Heat Exchanger Sub-Project Updates (OCP EMEA Summit 2025). Open Compute Project Foundation. OCP EMEA Summit 2025, Liquid Cooling track. OCP EMEA Summit 2025, Dublin. https://drive.google.com/file/d/1oRQe-41Vh3yBCFFUit-ost9himdgzUTV/view
Events on this subject
- SC26 – International Conference for High Performance Computing, Networking, Storage and Analysis
- NVIDIA GTC
- ISC High Performance
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