Hi eQuesters,
I am modeling a big box store that uses heat reclaim loop to recover energy from their refrigeration load. The store is to be located in Toronto, Canada.
I was wondering if anyone on these boards has had experience with using heat recovery in the refrigeration section of the zones?
I am hesitant on using the numbers I get from the Heat recovery feature in the refrigeration portion, as I can't see the math behind it.
Help files do not explain how this works and the hourly report doesn't have category specific to heat recovery from refrigeration.
Also if anyone has had experience even with what type of % reduction on the heating, that would be useful too.
Thanks,
Smith + Andersen
Rinkesh Shah, B. A. Sc.
Typically the amount of heat that can be recovered from refrigeration heat
reclaim is from 50% to 80% of the total heat of rejection of the
refrigeration system. It varies depending on the outside temperature, which
causes the refrigeration system head pressure and associated heat to drop.
Also, the refrigeration load placed on the refrigeration system various with
the outdoor ambient air temperature. If you only have refrigeration cases
and walk-ins that are all located inside of a temperature controlled store,
then the actual refrigeration load is 70-80% of the typical design BTUH
load, because the inside temperature of the building is like maybe 70
degrees F DB and 40 degrees F WB in winter, while the summer design is
75/55. If you have walk-in coolers that are located outside then the
refrigeration BTUH load can be dropped clear down to zero at times, in which
cause there is no refrigeration heat reclaim available at all. You will
have to look at your particular situation and use engineering judgment
accordingly.
If you model this you should vary the refrigeration load with the outside
air temperature and maybe use like 80% of the total heat of rejection for
recoverable heat.
David A. Bastow
Thanks to all that replied.
I had two major issues:
1) Heat recovery on refrigeration only sent the reclaimed heat back into the zones, not the case in my store
2) Doing a manual calculation using the hourly report would be taking credit where it doesn't exist as building could be in net heating mode as hourly report but AHU on the heat reclaim loop may not be calling for heat (particularly in my case where AHU serving sales area was part of the loop)
The way I ended up working this out was, I modeled the refrigeration as it is without the heat recovery option from the zone details. This gave me the hourly refrigeration demand from the hourly reports. Then I modeled the store only with zones that the heat is been recovered into, so that I can get hourly heating demand on for those zones. Combined the results in a new spreadsheet and took credit for whenever heating was demanded and refrigeration was available.
David: I haven't done the calculation yet on heat reclaimed vs heat rejection from the refrigeration but first look through and it seems to be in the high 60s range.
Smith + Andersen
Rinkesh Shah, B. A. Sc.