Wind turbine cooling technologies - Wind Power Generation and Wind Turbine Design - page 627

In addition that

t = f (cc, ch, v , Q )

( 14 )

c,out

13 c,in

t = f

14 ()

Q

(15 )

h,in

From eqns (13) and (15):

Δ= t f ( , cc, ch, c v )

( 16 ) m15 c,in

After substituting eqns (4), (12) and (16) into eqn (3), the functional relation of the
heat exchanger's thickness can be simplifi ed to:

= ( 17 )
On the basis of the deduced relational expression of the heat exchanger's thickness,
the thickness dimension is optimized with a method as follows.
Assume that when the wind turbine is running the wind speeds v c,in are under n
different circumstances and, thus, there will be n pairs of generated output values
and heat dissipation values corresponding to them. After choosing a dimension
pair of the fi n ('cc' and 'ch' in the equation), n different thicknesses of the heat
exchanger core unit (' c ') would be obtained, matching n circumstances, respec-
tively, according to the above equations. On this basis, by changing Z types of fi n
pairs on the air and liquid sides, Z heat exchanger core unit thicknesses meeting
design requirements ( c max1 , c max2 , …, c max z ) can be obtained; therefore Z corre-
sponding resistance on the liquid side and the heat exchanger weight can be
obtained. The optimization computing task of the heat exchanger core unit is to
fi nd an air-and-liquid-side fi n pair solution that not only can meet the cooling
demands under various working condition, but also is able to minimize the system
power consumption or the total weight of the system.

cf (cc, ch, v )

16 c,in

4.2.2 Optimization procedure of the heat exchanger core unit

1. As the wind turbine usually works under the condition that the wind speed

exceeds 8 m/s, thus only the condition with a wind speed ranging from 8 to
25 m/s will be considered. Giving a state point every time by increasing speed
of 1 m/s, the wind will be with 18 different velocities. The rated heat dissipating
capacity of the radiator corresponding to various wind velocities can be ob-
tained from the generator power graph, shown in Table 3 and Fig. 6.
Based on the overall consideration of the maximum rated inlet temperature 2.

required for the generator and the control converter as well as the temperature
rise of fl uid in the pipeline network, the radiator outlet ethylene glycol aqueous
solution temperature can be selected as: t h,out = 43°C. Other hypotheses are the
same with the statement in Section 4.1.
Assuming that the airside fi n and the liquid side fi n are selected from one of the

3.

fi ve types of straight fi ns and one of the fi ve types of serrated fi ns, respectively,
the collocation types for the air and liquid side fi n pairs sums up to 25, with
their specifi c parameters shown in Table 4.