Dear All,
We are faced with an ice cream factory where all the production spaces
and finished product warehouse spaces are cooled with ammonia absorption
chillers. We are trying to understand if there is any need to use the
eQuest Refrigeration version? What are the advantages of this over the
standard eQuest releases? As far as I know, the standard version can
also model absorption chillers. In which cases does it make sense to use
the Refrigeration version? What are your recommendations on how to
approach modeling this building?
Thank you,
Omer Moltay, LEED AP BD+C, BREEAM Assessor
The refrigeration version would allow the space temperatures typical of an ice cream factory. I can't remember the exact temperature, but you cannot model a space in the regular version of eQuest too much below 50-degrees-F. Also, I haven't seen many industrial ammonia absorbers but ammonia is a common low-temperature refrigerant. The refrigeration version has the components typical to a refrigeration plant (separate compressors, evaporators, and condensers) while the standard version would have to be forced into modeling it and certain components might not even be able to do that.
The refrigeration version is very powerful and I've used it on projects before, but it is a little bit more raw than the standard version. We had a complex project that required both ground-source heat pumps and refrigeration and unfortunately couldn't use just one version of eQuest to model the building, which made for an interesting process.
I have nothing against eQuest and we ended up with a solid model due partly to the software, but if I had to do such a complex model over again I would probably pick TRNSYS instead just due to the flexibility to build in multiple unique components. If your model is more of a standard refrigeration system, though, the refrigeration version of eQuest should be fine. I'd recommend getting in touch with the James Hirsch team for assistance if needed since the experience on the lists tends to be thinner on this topic. They were very helpful to us when we used the software.
Jeremy R. Poling, PE, LEED AP+BDC
Hey Jeremy!
Saw this post today and what weird timing... I have another unique/interesting scenario for a project on the horizon your advice/experience seems perfect for: A penguin exhibit for the local zoo!
Will have multiple zones targeting 46-48F. This model is primarily to explore different options with regard to just what equipment really makes sense from the outset and over the long term - a ground source wellfield is on the table as a definite option, and I gather our design team is very open to using entirely separate systems for the "cool" (68-70) vs. "cold" (46-48) zones.
Do you think design temps in the mid-high 40's might still crunch out alright with the regular eQuest version? I'm really not sure what to expect in the way of system options to be tossed at me, but it would help to have a solid understanding of the limitations moving forward... I think I'd prefer to stick with the tools I'm most familiar with if they remain feasible for the task at hand.
Jeff/Scott: Copying you gurus per Jeremy's advice - any thoughts?
Thanks fellas!
~Nick
NICK CATON, P.E.
Nick,
Such a coincidence :) I'm pretty sure Scott helped out my coworker Ken with a few items when he was working on the model I described below. Jeff and Scott are more than welcome to correct me if my memory is incorrect on any of this.
Here's the research I did over lunch trying to keep myself sane on where the low-limit on zone temps came from. If you look at the keywords, the DESIGN-COOL-T keyword has a range of 0-90 and will error on either side of that number, but the MIN_SUPPLY_T keyword has a range of 35-70 and the COOL-SET-T keyword has a range of 45-70. So effectively, the system will not be allowed to go below a cold deck leaving temperature of 45F. This will probably make it difficult to use for modeling the "cold" zones of the penguin exhibit but likely okay for the "cool" zones (Key part for Scott and Jeff to confirm).
The refrigeration model can handle packaged refrigeration equipment that can deal with the colder temperatures. The range you noted of 46-48 is pretty similar to the temperatures used in food processing and storage for "cooler" spaces as opposed to "freezer" spaces. That said, you would not be able to model a ground-source system in the refrigeration model, unless you find some really creative work-around that escaped us or wasn't available when we were doing our complicated model.
What we did to help mesh the models was to "fake" the portion of each model that wouldn't work 100%, created a common "back-of-house" portion of the model that was the same in both, then used the strengths of each version of eQuest to model the respective spaces. So in this case, you would end up with two separate models (and their respective baselines if you're ultimately using it for LEED or need to compare it to something):
1. eQuest-Standard Model: back-of-house as designed, "cool" spaces as designed, "cold" spaces faked as close as possible to represent the cold temperatures
2. eQuest-Refrigeration Model: back-of-house as designed, "cool" spaces faked to maintain temperatures without regard for system/energy, "cold" spaces as designed
As long as you meter everything out separately, your final energy use is the sum of the "cold" space meters from the eQuestR model, the "cool" spaces from the eQuest model, then we used the highest of the two back-of-house results to be conservative (there were minor differences that we didn't have enough time to ferret out the entire cause).
You can see why, with a huge amount of respect and thanks to Scott, Jeff, et.al...I'd almost rather put the time into learning the extra tool for my tool belt than try to do this again the same way :) I'd be curious to know if there have been any major changes to the Refrigeration model since then that might streamline the process we used?
Jeremy R. Poling, PE, LEED AP+BDC
Hi Nick. I?m working on a processing plant with some cold storage rooms
right now, and I?ve found you can get 35 degree supply air temps and
maintain room temps down to 37. If you?re using PSZ, it doesn?t use
COOL-SET-T but uses MIN-SUPPLY-T instead. I had to fudge the supply air
volumes with such a small dT, and change the curves as they didn?t make
sense at such low temps. But it seems to work.
I was very interested to hear there was a refrigeration version. That would
have been very handy for this project (too late now), as there are some
rooms below 35. I?ll try that next time.
Mike