Page 10 - European Energy Innovation - Winter 2014
P. 10
Winter 2014 European Energy Innovation


Falling film Falling film evaporators



evaporate, resulting in boiling water exits the pipes at the a simple and effective solution.
suppression. The highly viscous bottom and falls into the bottom In addition, it is important that
medium now runs through the tank. Replenishment condensate enough water is sent to the top
pipes and would lead to a very is also pumped into this tank. A of the pipe plate but also that the
low heat transfer coefficient fixed water level is maintained in water level is not too high. The
because of the low Reynolds the tank; this level controls the pump is adjusted so that enough
number. The use of turbulence supply of fresh condensate. From excess water is pumped upward.
promoters in the pipes somewhat this bottom tank, excess water is If the formation of steam reduces
eases this problem. However, led to the top of the pipe plate, (for example, because the process
the adverse boiling suppression where a special header ensures is running on a lower capacity),
means that this solution must also that every pipe is supplied with an overflow pipe is installed in
be eliminated. sufficient water and that this water the top tank so that the level can
is evenly distributed over the pipe never become too high.
This solution creates a situation CONCLUSION:
in which no liquid level is To compensate for the inferior The decision to use steam
maintained over the bundle and heat transfer coefficient of the generators based on the falling
no boiling suppression can take product, low-finned pipes are film principle results in equipment
place. This solution also involves used on the outside of the pipes with the highest possible steam
a vertical heat exchanger with thus the heat-transfer surface pressure and therefore a good
evaporating water in the pipes. is increased by roughly a factor investment. This is the best
This condensate flows downward of three by creating a threaded possible economic balance
from the top of the pipes as a profile on the pipes. between CAPEX and OPEX. l
thin film. On the way down, part
of the water evaporates and is The solution is a perfect example Contact details:
led upward as steam (against the of simplicity and robustness. It
current of the falling water). Due is controlled by means of two For more information or to
to the thin water film, the heat quantities. One involves the level find out what this can mean
transfer coefficient to the water in the bottom tank: this level for your system, send an email
is very high! The non-evaporated directly controls a valve for the to
supply of the fresh condensate,
   5   6   7   8   9   10   11   12   13   14   15