MAN Diesel
198 71 44-6.2MAN B&W 50 Mark 8/7/6, 46-26 Mark 9/8/7/6 engines
Jacket Cooling Water Temperature Control
When using a normal freshwater generator of the
singleeffect vacuum evaporator type, the fresh-
water production - based on the available jacket
cooling water heat Qjw - may, for guidance, be
estimated as 0.03 t/24h per 1 kW heat, i.e.:
M
fw
= 0.03 x Qjw t/24h 15%/0% [3]
where
M
fw
is the freshwater production in tons per 24
hours
and
Q
jw
is to be stated in kW
If necessary, all the actually available jacket cool-
ing water heat may be used provided that a spe-
cial temperature control system ensures that the
Valve A: ensures that T
jw
< 80° C
Valve B: ensures that T
jw
> 80 – 5° C = 75° C
Valve B and the corresponding bypass may be omitted if, for example, the freshwater generator is equipped with an automatic
start/stop function for too low jacket cooling water temperature
If necessary, all the actually available jacket cooling water heat may be utilised provided that a special temperature control system
ensures that the jacket cooling water temperature at the outlet from the engine does not fall below a certain level
178 23 700.0
Jacket cooling water systemFreshwater generator system
Expansion tank
Jacket cooling
water circuit
min
Tjw
max
Tjw
L
M
K
Seawater
In
Out
Condensator
Produced
freshwater
Evaporator
Brine out
B
Jacket water
cooler
Cooling
water
Deaerating tank
Jacket water pumps
Main engine
A
jacket cooling water temperature at the outlet from
the engine does not fall below a certain level. Such
a temperature control system may consist, e.g.,
of a special bypass pipe installed in the jacket
cooling water system, see Fig. 6.04.05, or a spe-
cial builtin temperature control in the freshwater
generator, e.g., an automatic start/stop function, or
similar.
If such a special temperature control is not ap-
plied, we recommend limiting the heat utilised to
maximum 50% of the heat actually available at
specified MCR, and only using the freshwater gen-
erator at engine loads above 50%. Considering the
cooler margin of 10% and the minus tolerance of
15%, this heat corresponds to 50 x(1.000.15)x0.9
= 38% of the jacket water cooler capacity Q
jw,M
used for dimensioning of the jacket water cooler.
Fig. 6.04.05: Freshwater generators. Jacket cooling water heat recovery flow diagram
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