Man B&W S50MC-C8-TII, Руководство по проекту, Страница: 186 / 403

MAN B&W 6.04
Page 7 of 12
MAN Diesel
198 72 12-9.0 MAN B&W S50MC-C8-TII
Calculation of Freshwater Production for Derated Engine
Example 2:
Freshwater production from a derated 6S50MC-C8-TII with high efficiency MAN Diesel turbocharger type
TCA and fixed pitch propeller.
Based on the engine ratings below, this example will show how to calculate the expected available jacket
cooling water heat removed from the diesel engine, together with the corresponding freshwater production
from a freshwater generator.
The calculation is made for the service rating (S) of the diesel engine being 80% of the specified MCR.
Nominal MCR, (L
1
) P
L1
: 9,960 kW (100.0%) and 127.0 r/min (100.0%)
Specified MCR, (M) P
M
: 8,466 kW (85.0%) and 114.3 r/min (90.0%)
Optmising point, (O) P
O
: 8,466 kW (85.0%) and 114.3 r/min (90.0%), P
O
= 100.0% of P
M
Service rating, (S) P
S
: 6,773 kW and 106.1 r/min, P
S
= 80.0% of P
M
and P
S
= 80.0% of P
O
Ambient reference conditions: 20 °C air and 18 °C cooling water.
The expected available jacket cooling water heat
at service rating is found as follows:
Q
jw,L1
= 1,450 kW from List of Capacities
Q
jw%
= 88.5% using 85.0% power and 90.0%
speed for O in Fig. 6.04.02
By means of equation [1], and using factor 0.88 for
actual ambient condition the heat dissipation in
the optmising point (O) is found:
Q
jw,O
= Q
jw,L1
x
Q
jw%
___
100
x 0.88
= 1,450 x
88.5
___
100
x 0.88 = 1,129 kW
By means of equation [2], the heat dissipation in
the service point (S) i.e. for 80.0% of optmising
power, is found:
k
p
= 0.852 using 80.0% in Fig. 6.04.04
Q
jw
= Q
jw,O
x k
p
= 1,129 x 0.852 = 962 kW
15%/0%
For the service point the corresponding expected
obtainable freshwater production from a freshwa-
ter generator of the single effect vacuum evapora-
tor type is then found from equation [3]:
M
fw
= 0.03 x Q
jw
= 0.03 x 962 = 28.9 t/24h
15%/0%