An Investigation of Multi-Parameters Effects on the Performance of Liquid-to-Liquid Heat Exchangers in Rack Level Cooling (ITherm 2023)

Overview

This record rests only on the abstract (metadata) of an experimental study presented at IEEE ITherm 2023. The study examines a rack-mounted liquid-to-liquid CDU feeding a multi-server rack of thermal test vehicles (TTVs) at several load levels. In the test set-up the CDU is connected to primary and secondary loops and serves the multi-server TTV rack at multiple heat loads. The full text is not in the record.

There are two performance indicators: stability of the coolant supply temperature and uniformity of TTV case temperatures. They were studied against different controller settings. This approach shows that not only the thermal capacity of the CDU but also the behaviour of its control loop determines the reliability of a liquid-cooled rack.

The main finding is that the integral (reset) term of the PID loop has the biggest effect on supply-temperature fluctuation; the integral coefficient was the most influential PID parameter for reducing it. It was also seen that small oscillations with amplitude under 1 C could grow into larger amplitudes under some settings.

The limit of the document is that only the abstract was assessed, and numeric tuning values, load levels and measurement uncertainty are not in the record. The result belongs to a specific CDU and test set-up, and generalising it would need further verification. For designers and commissioning teams the message is that CDU controller tuning should be verified across load steps.

Key points

1. Test set-up: rack-mount CDU connected to primary and secondary loops serving a multi-server TTV rack at multiple heat loads.
2. Target indicators: coolant supply temperature stability and TTV case-temperature uniformity.
3. The integral (reset) coefficient was the most influential PID parameter for reducing supply-temperature fluctuation.
4. Fluctuations with amplitude under 1 C could converge into larger oscillations depending on settings.
5. The record rests only on the abstract (metadata).
6. The study compares different controller settings.

Using it in design

• Record controller type and supply-temperature stability (e.g. +/- C) in CDU catalogue entries.
• Add a loop-tuning check of supply temperature stability across load steps to commissioning templates.
• Document the integral term as a separate parameter in controller settings.

Who should read it

Engineers who select, tune and commission CDUs for liquid-cooled racks.

Publication details

Authors

Ali Heydari; Qusai Soud; Mohammad Tradat; Ahmad Gharaibeh; Naimeh Fallahtafti; Pardeep Shahi; Jeremy Rodriguez; Bahgat Sammakia

Publisher

IEEE

Year

2023

Document number

DOI 10.1109/ITherm55368.2023.10177525

Event

IEEE ITherm 2023

Document language

English

Source type

Standard

Access

Citation only

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation