View Full Version : Extrapolation #2

26-02-2002, 07:38 PM
Now the customer wants me to survey processing from 45degF to 36degF. So prior to going out and re-do the whole thing with a new survey, I'm gonna try to plug it with Fridgetech's formula:

Safety factor is NOT included

Processing Room

ProductLoadOld = 14,700 btuh
XmissionInfiltMisc LoadOld = 151,200,000 btuh

45 RoomTempOld / 36 RoomTempNew * [151.2K XmissionInfiltMiscOld] = 189,000 btuh

[40 ProdArrivTempNew - 36 RoomTempNew] / [50 ProdArrivTempOld - 45 RoomTempOld] * 14,000 ProdLoadOld = 14,000 btuh

Load A + Load B = 203,000 btuh @ 18 hrs runtime

Product into processing is to come from 28degF cooler, but I must apply SOME load for product.

I'm heading out to take measurements, again.

26-02-2002, 11:16 PM
Just got back.

Room is 38ft(W) x 45ft(L) x 12ft cieling, 8in concrete with 3in polurethane, concrete floor. wall 1(L) adjoining 28degF cooler, Wall 2 (W) adjoining (50% 75degF occupied space and 50% 36deg Dock) Wall 3 (L) adjoining 75degF occupied space, and Wall 4(W) adjoining 90deg dry storage

30 horsepower equivalent (processing equipment)
40 people
All dock doors into equivalent or lower temp rooms EXCEPT one man door into occupied space
140,000 pounds beef entering from 28degF cooler

computer program results:

Wall heat gains = 27,320 btuh
Sens. infil. = 3,180
Lat inf. = 1,518
Prod Load = 0
Misc. Load = 174,250 btuh

total @18hr runtime = 206,268

The Fridgetech Formula (you otta' Trademark that) = 203,000 btuh

For the new application, I will adjust the system capacity to 16 hours runtime for assured off time for defrost.

08-03-2002, 06:18 PM
Originally posted by Fridgetech

That expression would only be valid if we were starting with a temperature of 0F and the load would be heating.

I don't understand that.

Are you suggesting "NewTemp/OldTemp? That would give a multiplier of (.8), and decrease load 20%.

Hey! This don't work at Freezer from 0deg to -10deg.

Now this seems to be more coincidental. You're messin' with me, aren't you!?

One thing I did do, however in the freezer situation, was since the product load increase is based on the ratios of dT of the product (old and new) which is somewhat imperical, I applied that percentage of change to the old Load. That seemed to get it into the ballpark... I'll need to consider that some more.......:rolleyes: