Page 322 - Practical Ship Design

280 Chapter 9

A Possible thermal
efficiency with
heat recuperation
Thermal efficiency without
heat recuperation
I
cooling water - Possible net heat recuperation
Possible heat
from exhaust gases
recuperation
\~
from jacket
11%
Heat required for
?@
/ heavy fuel oil system

Radiation losses
main engine’s/
auxiliaries ....! . Total heat of
c.......
......... ,/ exhaust gases
..A
(pumps etc.) e . . ...... .
.
Heat to engine
cooling systems-
Consumption Heat cons NB Figures in brackets
of auxiliary are kcallHPh
23 kcallH-v k,,,,
= 1.5%
Fig. 9.6. Typical heat balance diagram for a Sulzer RND diesel engine. (Abstracted from “The Modem
Diesel Engine and the New Trend of Transport and Energy Systems” by J.A. Smit (Sulzer) 1976.)

heaviest and cheapest grades of fuel oil are not acceptable fuels for auxiliary diesel
engines within the power bracket required to drive the size of generators fitted to
most ships.
The main engine(s) of most medium to large ships do, however, burn fuel oil, so
the use of a shaft- or gear-driven alternator provides a means of generating
electricity in a fuel efficient manner.
It is an added bonus that the use of such an alternator can provide a capital
saving since the addition of one cylinder to a slow-speed main engine will provide
the necessary additional power and generally cost quite a lot less than the saving
which can be made by reducing by one the number of diesel alternators.
The economics are, of course, more complicated than this, since means of
meeting the port electrical load and of providing standby generation must also be