CRE Details

• CRE Identifier:

  CRE-012

  Title of CRE:

  Cold Volume Thermal Control

  CRE Class:

  Class 1

  Status

  Implemented and Closed

  CRE Owner

  Kjetil Dohlen

  Sharepoint Link

  CRE Folder (SharePoint)

  
  

  Affected Documents listed in CRE

  No Associated Documents Listed!
  

  New/Updated Documents listed in CRE

  Resource Identifier	Version	Document Name	Main Author	Status	More Info	PDF Link
  HRM-00629	1	NGSS and FPRS Environmental Conditions	Fraser Clarke, University of Oxford	Obsolete

  CRE Notes

• Created by AJBorn and populated by KD.
• 2019-06-05: circulated to stakeholders for feedback.
• 2019-08-13: feedback received thus far indicates -15degC will need to be considered as an option.
• 2019-09-11: CCB held, need to confirm with ESO the issues regarding emissivity specifications.
• 2020-06-09: ESO have granted a waiver with regard to the surface temperature requirement (as per ET-894). This will be reflected in the relevant subsystem specifications.
• CCB 2020-06-15: Two issues here: adoption of a fixed temperature of -15degC rather than tracking 20degC below ambient, and a secondary issue of precisely which fixed temperature that should be. A trade-off of background radiation, optical stability in terms of the WCS, surface temperature and required cooling power. Fixed -15degC is the same as Ambient-20degC for the median case (represents a slight improvement in background radiation in warmer conditions, and vice-versa). ESO have already granted the necessary RfW for surface temperature, and fixed -15degC is better for electronics reliability and control. Original proposal -10degC, subsequently revised to -15degC following discussion. Current design has small cooling margin at the worst case, which suggests it has not been over-engineered.
• APPROVED FOR IMPLEMENTATION with the following Actions:
• AJBORN: update CRE to -15degC, and liaise with supporting document authors to update;
• identify who is tracking the risks in the Risk Register (lack of experience with this type of chiller plant). 2020-10-16: This change has now been implemented and is now closed, after an email exchage with Fraser and Hermine (MA).