Heat transfer is important in bioreactors for in situ sterilization and temperature control during fermentation. External heat transfer methods include jackets where water flows around the bioreactor vessel and external coils wrapped around the vessel. Internal heat exchangers submerged in the fermenter provide a large surface area for heat exchange but can interfere with mixing and be difficult to clean. External surface heat exchangers have better temperature control but require maintaining sterile conditions as the media passes through the external unit.

1. Heat transfer in bioreactor
PPRESENTED BY :: M JUNAID

2. Why we need it ?
1) In situ sterilization :-
Fermenter vessel is heated with steam and held at
constant temperature for some fixed time.
Cooling water is then used to bring the temperature
back to normal.
2) Temperature control during fermentation.

3. Modes of heat transfer
External control :-
Jacket: bioreactor is covered in a jacket between
which water flows to control temperature.
Coil: an external coil is wrapped around the
bioreactor vessel to control temperature.
The surface area for heat transfer is lower. but it is
good for small and lab scale fermenters. They are
easy to scale up.

4. Internal coil or exchanger
Internal coil are entirely submerged in fermenter and
provide large surface area for heat exchange.
Liquid velocity in the coil can be increased for better
temperature control.
DISADVANTAGE::
They interfere with mixing .
Cleaning of the vessel is difficult.
growth of microbial film on
heat exchanger.

5. External surface heat exchanger
An external heat exchanger unit has better heat
control capability.
Media pass from heat exchanger unit and re-enters
into the main vessel.
Sterile condition must be met.