Thermal performance for CellTank and CellReactor
Traditional thermal control of glass STR is by wrapping a flexible heating blanket around.
Most often thermal control is designed with PID control either relay or proportional control for max 40° liquid media temperature. As to the delay over the many barriers from heating blanket to thermo couple we see heating blanket reach +80°C – which is NOT recommended for Single-Use products.
In reality the typical setup involves
- a vessel, container with a polymeric wall surrounding a media volume
- the volume filled to some extent with media = thermal mass, thermal conductivity, mixing performance
- the thermocouple arranged inside the media = thermal delay
- the thermo couple arranged inside a polymeric tube = thermal delay, air gap
- air gap between heating blanket and vessel wall = thermal delay
- the thermal energy supplying device outside the vessel = vessel wall thermal conductivity
- a Process-Control-System with some kind of PID regulating mechanisms and conditions
This complicated setup is NOT stable or error free!
General precaution and improvements
- there must be a direct thermal connection between supply and measuring device
- thermal supply to be avoided on an empty vessel = vessel damage
- Insure appropriate cooling of heating blanket from the inner side of the vessel by the media!
- Improve performance, reduce SUB media gradient by wrapping insulation layer around the blanket and vessel. A sheet of bubble plastic foil is great
- Don’t arrange your bioreactor under an air-condition outlet
We recommended tightening torque is 10-20 Nm supplied by the one or more springs.