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Both water and
steam are used as heat
carriers in process heating systems. But
at temperatures above 100°C, water and steam
requires a corresponding higher operating
pressure.
In industrial heating
this high temperature level is often a
must in order to achieve the necessary high
output of the process. When establishing
the heating system with water and steam, you must deal
with systems and components of high
pressure and consequently the special
consideration in safety issues. This
means large dimensions, weights, more
safety procedures and thus
extra costs.
In thermal oil heaters (thermal oil
boilers), special oil-based thermal
fluid is used as the heat carrier -
instead of water or steam. This thermal
fluid (or heat transfer fluid)
operates at atmospheric pressure all the
way up to
300°C. Comparing this to water and steam, it
would require a corresponding pressure
of above 85 bar to obtain this temperature.
At higher temperature than 320-340°C the
thermal fluid too is pressurized (see
below). |
In the
principle the thermal fluid works as any
other heating fluid, it
is heated and cooled when passing through the system - exactly like low-temperature water application for domestic use (house heating). Only here
the operating temperature is much
higher, and therefore both the system and the components are quite different.
It other words, the design of thermal
oil
systems and the parts hereof required not only special
skilled engineers - it also require that
they have many years experience to deal
with individual challenges that always
exists in such installations.
Thermal
oil heaters must be designed for
operating with the
special thermal fluid for high temperature
application. It is still an oil that be
might flammable and fatal if not dealt
with the correct way - and this issue is
very important to remember throughout
the design and installation stage.
Where water heaters can be heated as a
pool, the thermal
fluid must be heated by forced circulation
ensuring high velocity of the oil at all
time ensuring low film temperature to
avoid cracking. |
