Russian Journal of Applied Chemistry, 2011, Vol. 83, No. 3, pp. 539−541.
Pleiades Publishing, Ltd., 2011.
Original Russian Text
N.A. Voinov, O.P. Zhukov, A.N. Voinov, 2010, published in Khimicheskaya Promyshlennost’, 2010, Vol. 87, No. 8, pp. 389−391.
PROCESSES AND DEVICES
OF CHEMICAL MANUFACTURES
Enchancing Heat Exchange in the Tubular Film Evaporator
N. A. Voinov, O. P. Zhukov, and A. N. Voinov
Siberian State Technological University, Krasnoyarsk, Russia
Received November 15, 2010
Abstract—Condensation of a vapor –air mixture and boiling in a ﬂ owing down water ﬁ lm in an upright tubular
evaporator was examined. We studied techniques to intensify heat exchange by installation of turbulators in
a form of coil on a heat transfer surface of pipes and developed dependencies to estimate values of heat transfer
coefﬁ cient in condensation and boiling.
Tubular evaporators with ﬂ owing down ﬁ lm are
widely used in industrial evaporation, distillation, and
water treatment and desalination. They are very efﬁ cient
at comparatively small useful temperature difference
(3–6°С) with low temperature depression (0.5°С).
Moreover, their period of a contact with a heat transfer
surface is small (3–10 s). A large metal consuming of
the ﬁ lm evaporators is their essential disadvantage along
with non-stationary ﬁ lm ﬂ ow of operational medium in
it due to formation of dry spots on a smooth surface of
Enhancing the heat transfer using a screw roughness
on ﬁ lm-forming surfaces is one of effective ways to
reduce an effect of the disadvantages. A diffusion
resistance at a boundary of vapor–liquid, a temperature
gradient of the steam ﬂ ow, and thermal resistance of
a turbulent condensate ﬁ lm exert the largest inﬂ uence
on the intensity of vapor condensation.
Various shaped surfaces [1–2] are employed to
enhance heat exchange in ﬁ lm condensation of vapor,
that allow a decrease in the thermal resistance of
a condensate ﬁ lm due to reducing its thickness and
stirring. However, use of the shaped surfaces for reducing
the diffusion resistance and leveling temperature
proﬁ les in condensation of air–vapor mixture is not
entirely effective and development of new way of the
heat exchange intensiﬁ cation is required.
The main array of accumulated data on boiling
was obtained in examination of processes in a liquid
ﬁ lm ﬂ owing down over hydraulically smooth heat
transferring surface. It was noted that at a low liquid
ﬂ ow and certain heat load a formation of unwetted
spots on a wall occurs and that exerts negative effect on
operation of the apparatus.
In addition, it would be advisably in the ﬁ lm boiling
to place various types of artiﬁ cial roughness though its
effect of heat transfer intensity is insufﬁ ciently studied
and necessitates further investigation.
Vapor condensation. In this paper we studied a way
of intensiﬁ cation vapor condensation by creating the
circular vortices on an interphase surface which are
formed as a result of moving the vapor ﬂ ow along the
bodies of a spiral shape installed with gap relative to
a heat transfer surface (Fig. 1).
The installation of a spiral into a pipe with a gap
relative to its wall allows increasing the heat transfer
coefﬁ cient up to 3 times (Figs. 1a, 2). In this case heat
transfer intensiﬁ cation occurs both in air-vapor mixture
condensation and in condensation of solely vapor.
Then we can assume that mixing vapor by the circular
vortices on the interphase surfaces favors removal of
not condensed gases and also leads to leveling of the
temperature proﬁ les in ﬂ ow. As our studies have shown
the maximum intensiﬁ cation of heat transfer was