The cool down time can be calculated by using the same formula as above.
t = V x ΔT x K
60 x W where:
t = Heating time (minutes)
V = Total liquid volume (litres L)
ΔT = Temperature difference (ºC)
K = Liquid heat capacity (J/L/ºC)
For water: K = 4200
For silicone oil: K = 1680
W = Heating power (Watt)
However, as the temperature decreases the cooling power of the circulator reduces, it is therefore necessary to estimate the average cooling power across the temperature range to be cooled.
Cooling power Watts = Cooling power at lower temperature + Cooling power at upper temperature/2
An example: For a 6 litre cooling bath with a cooling power of 1000W at +20°C and 500W at 5°C using water, the cool down time from +20°C to 5°C will be:
t = 6 x 15 x 4200 = 8.4 mins
60 x (1000+500)/2