Man B&W L35MC6-TII User Manual

MAN B&W 6.04
Page 5 of 12
MAN Diesel
MAN B&W S50MC/MC-C-TII, S46MC-C-TII, S42MC-TII,
S40MC-C-TII, S35MC/MC-C-TII, L35MC-TII, S26MC-TII
198 71 42-2.0
Freshwater Generator
If a freshwater generator is installed and is utilis-
ing the heat in the jacket water cooling system,
it should be noted that the actual available heat
in the jacket cooling water system is lower than
indicated by the heat dissipation figures valid for
nominal MCR (L
1
) given in the List of Capacities.
This is because the latter figures are used for
dimensioning the jacket water cooler and hence
incorporate a safety margin which can be needed
when the engine is operating under conditions
such as, e.g. overload. Normally, this margin is
10% at nominal MCR.
Calculation Method
For a derated diesel engine, i.e. an engine having
a specified MCR (M) equal to optimising point (O)
different from L
1
, the relative jacket water heat dis-
sipation for point M and O may be found, as previ-
ously described, by means of Fig. 6.04.02.
At part load operation, lower than optimising
power, the actual jacket water heat dissipation will
be reduced according to the curves for fixed pitch
propeller (FPP) or for constant speed, controllable
pitch propeller (CPP), respectively, in Fig. 6.04.04.
With reference to the above, the heat actually
available for a derated diesel engine may then be
found as follows:
1. Engine power equal to specified MCR
power M (equal to optimising point O).
For specified MCR (M) = optimising power
(O), the diagram Fig. 6.04.02 is to be used,
i.e. giving the percentage correction factor
‘Q
jw%
’ and hence for optimising power P
O
:
Q
jw,O
= Q
jw,L1
x
Q
jw%
___
100
x 0.9 (0.88) [1]
2. Engine power lower than optimising power.
For powers lower than the optimising power,
the value Q
jw,O
found for point O by means of
the above equation [1] is to be multiplied by
the correction factor k
p
found in Fig. 6.04.04
and hence
Q
jw
= Q
jw,O
x k
p
15%/0% [2]
where
Part load correction factor for jacket
cooling water heat dissipation
Engine load, % of optimising power (O)
FPP : Fixed pitch propeller
CPP : Controllable pitch propeller, constant speed
k
p
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 10 20 30 40 50 60 70 80 90
100%
FPP
CPP
178 59 45-7.0
Fig. 6.04.04: Correction factor ‘kp’ for jacket cooling
water heat dissipation at part load, relative to heat dis-
sipation at optimising power
FPP : k
p
= 0.742 x
P
S
__
P
O
+ 0.258
CPP : k
p
= 0.822 x
P
S
__
P
O
+ 0.178
Q
jw
= jacket water heat dissipation
Q
jw,L1
= jacket water heat dissipation at nominal
MCR (L
1
)
Q
jw%
= percentage correction factor from
Fig. 6.04.02
Q
jw,O
= jacket water heat dissipation at optimising
power (O), found by means of equation [1]
k
p
= part load correction factor from Fig. 6.04.04
0.9 = factor for safety margin of cooler, tropical
ambient conditions
The heat dissipation is assumed to be more or less
independent of the ambient temperature conditions,
yet the safety margin/ambient condition factor of
about 0.88 instead of 0.90 will be more accurate for
ambient conditions corresponding to ISO tempera-
tures or lower. The heat dissipation tolerance from
15% to 0% stated above is based on experience.

Man B&W L35MC6-TII Specifications

General

Brand	Man
Model	B&W L35MC6-TII
Category	Engine
Language	English