Man B&W S50ME-B9.3-TII, Project Manual

Page: 144 / 337

MAN B&W 6.04
Page 3 of 12
MAN Diesel
198 90 83-3.0 MAN B&W S50ME-B9.3\-TII
Calculation of List of Capacities for Derated Engine
Example 1:
Pump and cooler capacities for a derated 6S50ME-B9.3-TII with 1 high efficiency MAN TCA55-26
turbocharger , high load, fixed pitch propeller and central cooling water system.
Nominal MCR, (L
1
) P
L1
: 10,680 kW (100.0%) and 117.0 r/min (100.0%)
Specified MCR, (M) P
M
: 9,612 kW (90.0%) and 111.2 r/min (95.0%)
Total cooling water flow through scavenge air
coolers
V
cw,air,M
= V
cw,air,L1
x Q
air%
/ 100
V
cw,air,M
= 146 x 0.874 = 128 m
3
/h
Cooling water flow through lubricating oil cooler
V
cw,lub,M
= V
cw,lub,L1
x Q
lub%
/ 100
V
cw,lub,M
= 110 x 0.958 = 105 m
3
/h
Cooling water flow through central cooler
(Central cooling water pump)
V
cw,cent,M
= V
cw,air,M
+ V
cw,lub,M
V
cw,cent,M
= 128 + 105 = 233 m
3
/h
Cooling water flow through jacket water cooler
(as for lube oil cooler)
V
cw,jw,M
= V
cw,lub,M
V
cw,jw,M
= 105 m
3
/h
Seawater pump for central cooler
As the seawater pump capacity and the central
cooler heat dissipation for the nominal rated en-
gine found in the ‘List of Capacities’ are 326 m
3
/h
and 6,670 kW the derated seawater pump flow
equals:
Seawater pump:
V
sw,cent,M
= V
sw,cent,L1
x Q
cent,M
/ Q
cent,L1
= 326 x 5,986 / 6,670 = 293 m
3
/h
The method of calculating the reduced capaci-
ties for point M (n
M%
= 95.0% and P
M%
= 90.0%) is
shown below.
The values valid for the nominal rated engine are
found in the ‘List of Capacities’, Figs. 6.03.01 and
6.03.02, and are listed together with the result in
the figure on the next page.
Heat dissipation of scavenge air cooler
Fig. 6.04.01 which approximately indicates a Q
air%
= 87.4% heat dissipation, i.e.:
Q
air,M
=Q
air,L1
x Q
air%
/ 100
Q
air,M
= 4,080 x 0.874 = 3,566 kW
Heat dissipation of jacket water cooler
Fig. 6.04.02 indicates a Q
jw%
= 92.2% heat dissi-
pation; i.e.:
Q
jw,M
= Q
jw,L1
x Q
jw%
/ 100
Q
jw,M
= 1,690 x 0.922 = 1,558 kW
Heat dissipation of lube oil cooler
Fig. 6.04.03 indicates a Q
lub%
= 95.8% heat dis-
sipation; i.e.:
Q
lub,M
= Q
lub, L1
x Q
lub%
/ 100
Q
lub,M
= 900 x 0.958 = 862 kW
Heat dissipation of central water cooler
Q
cent,M
= Q
air,M
+ Q
jw,M
+ Q
lub, M
Q
cent,M
= 3,566 + 1,558 + 862 = 5,986 kW