Page 210 - Handbook of Energy Engineering Calculations

FIGURE 6 Slant diagrams for internal-combustion engine heat
exchangers. (Power.)

Two-cycle engines may have a larger exhaust-gas flow than four-cycle
engines because of the scavenging air. However, the exhaust temperature will
usually be 50 to 100°F (27.7 to 55.6°C) lower, reducing the quantity of steam
generated.

Where a dry exhaust manifold is used on an engine, the heat rejection to
the cooling system is reduced by about 7.5 percent. Heat rejected to the
aftercooler cooling water is about 3.5 percent of the total heat input to the
engine. About 2.5 percent of the total heat input to the engine is rejected by

the turbocharger jacket.
The jacket cooling water absorbs 11 to 14 percent of the total heat
supplied. From 3 to 6 percent of the total heat supplied to the engine is
rejected in the oil cooler.

The total heat supplied to an engine = (engine output, bhp)[heat rate,
Btu/(bhp · h)]. A jacket-water flow rate of 0.25 to 0.60 gal/(min · bhp) (0.02
to 0.05 kg/kW) is usually recommended. The normal jacket-water
temperature rise is 10°F (5.6°C); with a jacket-water outlet temperature of

180°F (82.2°C) or higher, the temperature rise of the jacket water is usually
held to 7°F (3.9°C) or less.
To keep the cooling-water system pressure loss within reasonable limits,