"Yale University District Cooling Systems Capacity & Operations Improvements"

Hemant Mehta, PE, WM Group Engineers.

To summarize:

  • Many district cooling systems operate inefficiently, resulting in significant extra operating costs and greatly reduced system capacity.
  • All three components of the chilled water system (building system, distribution system, plant) should be compatible to each others.
  • Install two-stage coil control for the air handlig units chilled water coils. First stage is to reduce flow until it enters critical zone. Second state is to maintain flow and increase supply temperature.
  • Design building control valves so that they can always close against the system shut-off pressure.
  • Avoid bypass between supply and return lines. No virgin water should go back to the plant.
  • Do not mix variable volume and constant volume systems in a district system.
  • If properly designed, an all primary system is ideally suited for a district chilled water system with multiple chillers.
  • Before designing plant modifications, review systems flows, temperature, and pressures. Design modifications to optimize the system around existing operating condition.
  • Every plant must have a design criteria for building system connection.