When working with a closed loop system, what is the recommended ratio of bath volume to external closed circuit volume?
The volume of the external circuit should not exceed 50% of the bath volume. Therefore, special care should be taken when selecting a suitable bath. If the external volume is too large, too much time will be spent cooling the liquid in the external circuit. The subsequent temperature differential between the external circuit and internal bath impedes the circulator’s capacity to maintain accurate temperature control. Another consideration is the effect of volumetric expansion. In a closed circuit, the thermostat must withstand the total volumetric expansion of the circulating liquid, as well as the liquid inside the thermostat. When the external closed circuit is 50% of the bath volume, the volume is increased by 13% per 100°C. Over a larger temperature range, the expansion can quickly exceed the difference between the circulator’s maximum and minimum volume, also know as the “buffer volume” Lauda offers circulators with an especially large buffer volume, such as Model K12-KS, Model K1
