Wind turbine cooling technologies - Wind Power Generation and Wind Turbine Design - page 625

4.1.3.4 Anti-corrosion measures
The heat exchanger exposed to the external environment is prone to be corroded,
which will affect the durable, reliable operation of the heat exchanger. Therefore,
necessary anti-corrosion treatments need to be implemented, like coating the alu-
minum fl akes with anti-corrosive allyl resin coverings and employing hydrophilic
membranes on its outer surface. Having been treated with this method, the acid
rainproof of the aluminum fi ns and the anti-salt corrosion property can be 5-6 times
as large as those of the ordinary ones. In the design of the heat exchanger, due to
relatively large difference of the cooling system operating loads in winter and
summer, the summer operating mode is adopted as the design condition, while the
heat transfer effi ciency can be controlled through a bypassing method in winter.

4.1.4 Flow resistance calculation of the liquid cooling system
and pump selection
The liquid cooling pipeline system is comprised of a steel tube part and a pressure
hose part. In view of the various factors, the following pipe diameters should be
selected: steel tube and pressure hose diameter of the main trunk D 1 = 48 mm,
branch steel tube and pressure hose's diameter D 2 = 42 mm. The on-way resistance
and local resistance can be calculated based on the selected tube diameter, with
which the circulating pump can be selected.

4.2 Optimization of the liquid cooling system

Based on the design method mentioned above, by utilizing MATLAB software, the
optimization of the liquid cooling system is performed. Since the external radiator
is the core component of the liquid cooling system, its structural dimension has an
important impact on the cooling effect of the wind turbine and the weight of the
nacelle. The subject of optimization in this section is the external radiator shown in
Fig. 5. The constraint conditions are: the external radiator is fi xed in the frame on
top of the rear of the nacelle, with a limitation of frame size of 1.900 m

0.200 m; and the actual maximum size of the core unit of the external radiator is
1.800 m

× 0.820 m ×

0.200 m excluding the size of stream sheet and head. Under
these conditions, the optimization procedure is shown as follows.

× 0.800 m ×

4.2.1 Derivation of the thickness of the heat exchanger core unit
The functional relation of the thickness of the heat exchanger can be derived from
the heat transfer equation and the heat transfer coeffi cient equation and so forth
as follows:
Total heat transfer:

(1 )

QktF =Δ

hmh

where Q is the heat transfer quantity of the heat exchanger, k h is the total heat
transfer coeffi cient on the liquid side,

t m is the heat transfer mean temperature
difference, F h is the total heat transfer area on the liquid side, given as

Δ