A major factor driving the decision on which circulator will best control the temperature of a process within a chemical reactor is the cooling power at the process temperature.
However, this figure alone is meaningless when considered on its own. The size of the reservoir must also be taken into account since this makes up a significant fraction of the total thermal load.
The real factor to consider is the awatts per litre' ratio. Simply put, a 2 litre kettle filled to the top with a 1 kW heater (giving 500 w/l) will take twice as long to boil compared to the same kettle with only 1 litre of water (now 1000 w/l). A circulator with 1 kW of cooling power and a 20 litre bath has a watts/litre ratio of 50 w/l. That means you pay for 1000 watts but your process only sees 50 watts/litre!
The real impact of a large volume is in response times to dynamic thermal loads such as a sudden increase during a reaction. The speed at which the temperature of the jacket can be changed in order to remove heat is crucial to the thermal control of the reaction.
The higher the watts/litre ratio, the more responsive and tighter the control will be.
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Huber Kältemaschinenbau GmbH is based in Offenburg, Germany. www.huber-online.com
