First experiment to characterize the ability of my Frysta BF100 and compare it with using my regular kitchen fridge's freezer. Warning: there is math at the end...
I filled each of two 1-gallon Ziploc freezer bags with 2 quarts (1.89kg) of tap water. Each was set out on a counter until they reached 65F (18.3c) as measured with my Thermapen:
I plugged in the Frysta, installed the just received GN1/2 tray, set it to -22F (-30c) and let it pre-chill for half an hour.
I then placed one of the bags in my regular freezer, which is set to 0F and heavily loaded with stock, ice cream, etc.:
The other bag I placed in the Frysta tray with the temperature probe in the water:
I closed my freezer door, closed the Frysta door and checked the Frysta probe temp. It reported 61F (16.1c), 4F below the Thermapen measurement.
I set the Frysta to Hard Blast Freeze, 4 hours, -22F, and after the annoying Frysta compressor and evaporator fan start delay, we were off.
The Frysta probe temp reported 31F (-0.5c) after 37 minutes. I checked my kitchen freezer bag at that time with the Thermapen and recorded a temp of 42F (5.5c). However, since the initial Frysta probe temp didn't match the Thermapen, I watched for the temperature drop stall, which happened at a reported 29F (-1.7c), so that was when the machine actually hit a real 32F (0c). So the Frysta was again off by about 3-4F, so its water was at about 35F when my regular freezer's was at 42F.
65F to 35F in the Frysta in the same time my kitchen freezer took to get from 65F to 42F...
At that point the Frysta was extracting latent heat for the liquid to solid phase transition, so there was no temperature change for quite a while.
The Frysta temperature finally starting dropping again right at the 3 hour mark. I checked the bag of ice in my kitchen freezer. It was almost completely frozen. Not exactly an impressive showing by the Frysta...
I let the Frysta continue until it reported a probe temp of -1F (-18.3c) 3 hours and 27 minutes after the Blast Freezing started.
Now for the math...
Over the course of 3:27 (12420s) the Frysta removed about 904kJ from the water:
(liquid->solid transition) + (temperature drop)
(1.893kg x 334kJ/kg) + (1.893 kg x 4.184kJ/kgc x 34.4c) = 904kJ
Which is about 72.8J/s:
904kJ/12420s = 72.8J/s
The Frysta User Manual claims that the BF100 capacity is 3kg from +90C to -18C in 240 minutes. If that food were pure water that would require removal of about 2360kJ:
(liquid->solid transition) + (temperature drop)
(3kg x 334kJ/kg) + (3kg x 4.184kJ/kgc x 108c) = 2360kJ
Which is about 164J/s:
2360kJ/14400s = 164J/s
Blast freezers seem to be commonly rated by weight capacity, which implies that there's a standard food defined with a specified latent heat of fusion and specific heat behind the ratings, but a few minutes of Googling hasn't turned it up for me yet...
