View Full Version : here is a load calc for u guys
07-26-2005, 06:50 PM
8x20x8ft high walkin freezer.
1 standard 4ft door
4inch r20 prefab walls
4inch prefab floor
95F maximum outdoor ambient
0F box temperature
8000 lbs of carbon based resin(liquid form)
sorry dont know specific heat of product( i used specific heat of honey as a comparison)
cooled to 0F in 24 hours
i came up with a 36000btuh load with a 10F TD on coil.R404A
just want to double check my numbers
[Edited by lowtemp on 07-26-2005 at 06:52 PM]
07-26-2005, 07:33 PM
what is product enetering temp
load can be 80000 or 120000
chances quite high that r20 will collapse with time
insist on standard refrig insulation
07-26-2005, 08:37 PM
You should know the thermodynamic characteristics of this material and how they are packaging it before doing anything further.
In addition to the specific heat you need to address the latent heat of fusion as I suspect this material has a freeze point somewhere above 0ºF. That can make a huge difference in your load calcs.
The packaging aspect is equally important. If you consider that it takes longer to completely freeze a 5 gallon bucket of water than it does to freeze an 8 oz bottle at 0ºF. Then, what if they have pallets of 5 gallon buckets of this resin all shrink-wrapped, tightly packed and stacked in the middle of the room? The bucket at the center bottom will hardly get chilled in 24 hrs, let alone frozen and down to zero.
Be careful as to what you guarantee.
07-26-2005, 09:12 PM
the product is going in at 75F.The product is in steel drums with perferated lids. They are getting me chemical make up of resin. They are not freezing product.The freeze point is -35F. They just need to keep it at 0F. the freezer is constructed out of 4" isowall panels(Coldmatic).
07-27-2005, 01:32 PM
I come up with a touch under 50K per hour, given default conditions, and no further details on the product itself. This contains a 10% error factor.
07-27-2005, 05:57 PM
if what you say is correct 50,000 btuh would be ok
I don't believe -35 freeze point and that may
double your load (Latent HOR)
just be careful
07-27-2005, 07:35 PM
What are the "traffic" conditions of this box?
Electric pallet jack or propane forklift? Or neither?
Once the product is down to temp, how long will it be kept inside freezer PRIOR to removal?
In other words ... if part of your load is brought down to temp and left idle ... then some are removed and new loads are carted in .... not the entire load of drums will be adding heat load to your system.
See what I mean?
If your sizing for worse case scenario ... fine. You will definately end up with some extra horsepower. Never a bad idea.
But if your load is being brought in, heat is removed to where zero is your product temp and then 24 hours later the product is being switched out ....en-masse, then you will never relax your system.
It will always be under tough workload.
So size accordingly. And size using multiple systems. Dont put all your horsepower on one crankshaft.
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