Power Plant Engineering

404 POWER PLANT ENGINEERING

Artificial means for increasing the surface
area without increasing the cubical contents have,
therefore, been developed. These comprise special
tank constructions such as
(a) Fins, welded vertically to the tank sides;
(b) Corrugations;
(c) Round- or elliptical-section tubes;
(d) Auxiliary radiator tanks.
These are illustrated in Fig. 12.25. Little
need be said of (a) or (b), the former being not
very effective and the latter rather difficult in con-
struction, although formerly used in Europe.
Method (c) is extremely common for a wide range
of sizes, while (d) is used when there is insuffi-
cient room to accommodate all the tubes required
by a large transformer.

The tabbed tank provides considerable cooling surface, and the tubes being connected with the
tank at the top and bottom only provide a head sufficient to generate a syphoning action; which im-
proves the oil circulation quite apart from enhanced cooling. The tubes may sometimes be "gilled," i.e.
wound with a strip-on-edge metal helix, to increase cooling surface and the eddying airflow that more
effectively removes heat. The baffling action, however, also tends to restrict the total sir flow so that the
net gain is not commensurate with the added cooling surface.

Ribs or Fins

Oil

Ta n k w a l l

Corrugations

Oil

()a

()b

Tu b e s

()c ()d

Radiator

tank

Main tank

Ambient temp

CoreDuctL.V.DuctH.V.

AirTemperature-rise, °C

70

60

50

40

30

20

10

0

Fig. 12.24. Oil-Circulation and Temperature

Distribution.