Heating/cooling a volume of air.
I have a box that is 5'w x 5'l x 3.3'h and the air temperature within the box is 60F. If I have a device that can heat the air in the box to 80F in 7 minutes, then what formula could I use to determine how long it would take that same device to heat a box exactly 3 times the size of the first box (15'w x 15'l x 10'h) from 60F to 80F?
I know its not going to be a linear (7min x 3 = 21 min) equation because larger volumes of gas or liquid take longer to cool or heat than smaller volumes.
In addition, could this same formula be applied to determine how long it would take either boxes to heat from 60F to 90F, or possibly to cool from 90F to 50F? I am hoping to find a general formula that can be applied to a variety of heating/cooling scenarios.