Page 215 - Handbook of Energy Engineering Calculations

TABLE 7 Air Density at Various Elevations *

An engine radiates 2 to 5 percent of its total heat input. The total heat input
= (engine output, bhp) [heat rate, Btu/(bhp · h)]. Provide 12 to 20 air changes

per hour for the engine room. The most effective ventilators are power-driven
exhaust fans or roof ventilators. Where the heat load is high, 100 air changes
per hour may be provided. Auxiliary-equipment rooms require 10 air changes

per hour. Windows, louvers, or power-driven fans are used. A four-cycle
3
3
engine requires 3 to 3.5 ft /min of air per bhp (0.11 to 0.13 m /kW); a two-
3
3
cycle engine, 4 to 5 ft /(min · bhp) (0.15 to 0.19 m /kW).
The method presented here is the work of John P. Callaghan, reported in
Power.

BYPASS COOLING-SYSTEM DESIGN FOR I-C ENGINES

The internal-combustion engine in Fig. 7 is rated at 402 hp (300 kW) at 514
r/min and dissipates 3500 Btu/(bhp · h) (1375 W/kW) at full load to the
cooling water from the power cylinders and water-cooled exhaust manifold.
Determine the required cooling-water flow rate if there is a 10°F (5.6°C)

temperature rise during passage of the water through the engine. Size the
piping for the cooling system, using the head-loss data in Fig. 8, and the
pump characteristic curve, Fig. 9. Choose a surge tank of suitable capacity.

Determine the net positive suction head requirements for this engine. The
total length of straight piping in the cooling system is 45 ft (13.7 m). The
engine is located 500 ft (152.4 m) above sea level.