Twist Flate-tube （Twisted tube）Heat Exchanger
Twist flat-tube is one kind of enhanced heat transfer tubes that
were firstly presented by Swiss Allares Company, and then improved
by the United States Brown company.
2.1 Structure and manufacture of twist flat-tube
The characteristic of twist flat-tube is that every cross section
of the tube is oval, when assemble heat exchangers they can be
mixed bundle (that is, the mixed use of twist flat-tube and bare
tube), and can also be a pure twist flat-tube bundle.
The manufacturing process includes two forming steps: "partial
pressure" and "distortion". The tube cross section is ellipse type
the ratio of long and short axis is designed according to the flow
velocity in heat transfer tube. When the flow rate in tube is low,
we can increase the ratio of the long and short axis, or reduce the
2.2 Enhanced heat transfer principles of twist flat-tube
The unique structure of twist flat-tube can make the flow in tube
pass and shell pass in the spiral motion at the same time, in this
way it enhanced the turbulent intensity. The heat transfer
coefficient of the twist flat-tube is 40% higher than the normal
one, but the pressure drop is almost the same.
2.3 Advantages of heat exchanger with twist flat-tube
1Lower pressure dropNo baffle plate, lower pressure drop in the
2Higher heat transfer efficiencyIt can increase the turbulent
make the shell flow velocity and the direction
change regularly, and enhance the mixture in
3Less depositNo blind zone in the shell
2.4 Specification of twist flat-tube heat exchanger
Fig: Basic dimension parameter figure of twist flat-tube
Table: Basic parameter table of twist flat-tube
Spec.Lead St(mm)Long axis of twist flat-tube a(mm)Length of two
ends bare tube(mm)
14x1.515020025030016.0 Arbitrary length
Note: The above table is the basic parameter of standard twist
flat-tube.Twist flat-tube can be manufactured according to St and L
, if there are special requirements.
2.5 Application of the twist flat-tube
As twist flat-tube has developed and improved fastly in recent
years, it is much more reliable and effective, and almost can be
used in all shell and tube heat exchangers. More than 400 twist
flat-tube heat exchangers have been used since 1984, and they can
be used in gas-gas, liquid-liquid and liquid-gas heat transfer
process, including chemistry, petroleum, food, papermaking,
electric power, metallurgy, mining, and urban heating industry.
2.6 Application example
In 1997, Lanzhou refinery changed the traditional heat exchangers
in the Ketone benzene dewaxing unit into the twist flat-tube heat
exchangers, which were designed and fabricated by a local company.
According to the process parameters, the HETECH was used for the
type selection calculation of twist flat-tube heat exchanger.
Table: Related parameters of benzol-ketone dewaxing process
ItemTube passShell pass