Does OS GUI support transcritical CO2 booster systems?

asked 2019-04-21 03:28:09 -0500

Tilstergirl gravatar image

updated 2019-04-21 08:27:22 -0500

Hi folks, I'm trying to model a typical CO2 booster system for a supermarket with MT and LT branches. I can see that EnergyPlus has objects for transcritical operation but I'm struggling to understand how to build it in OS. The comments in https://unmethours.com/question/3999/... suggest that transcritical operation is supported within the model but not the GUI, but that was some years ago. I can't see any transcritical components/measures in the BCL. So I think I have four questions, although perhaps one answer will cover them all:

  1. I can see that OS compressor components have an option to choose subcritical or transcritical operation, but there is nowhere to put the "Transition Temperature" (as it is termed in EP InputOuput Reference).
  2. The Input Output guide suggests that the gas cooler performance assumes an approach temp of 3 degrees in transcritical mode, and a delta T of 10 degrees in subcritical mode. But if sub/transcriticality is a property of the compressor, how does the gas cooler "know" which state it is in?
  3. The refrigeration template in OS does not seem to accomodate a booster compressor nor any way to model gas mixing - should I model this as a cascade system with a perfect heat exchanger? How would this cope with the change in refrigerant mass at different points in the circuit?
  4. The OS refrigeration tempate does not seem to support heat recovery. Is there something I can do to model this?

Very much a beginner here so apologies if I've missed something obvious. Any help is appreciated!

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