Page 211 - Handbook of Energy Engineering Calculations

some designers recommend a pipe velocity equal to the nominal pipe size
used in the system, or 2 ft/s for 2-in pipe (0.6 m/s for 50.8-mm); 3 ft/s for 3-
in pipe (0.9 m/s for 76.2-mm); etc. The maximum recommended velocity is
10 ft/s for 10 in (3.0 m/s for 254 mm) and larger pipes. Compute the actual
0.5
pipe diameter from d = (G/2.5 v) , where G = cooling-water flow, gal/min; v
= water velocity, ft/s.
Air needed for a four-cycle high-output turbocharged diesel engine is
3
3
3
3
about 3.5 ft /(min · bhp) (0.13 m /kW); 4.5 ft /(min · bhp) (0.17 m /kW) for
3
a two-cycle engine. Exhaust-gas flow is about 8.4 ft /(min · bhp) (0.32
3
3
3
m /kW) for a four-cycle diesel engine; 13 ft /(min · bhp) (0.49 m /kW) for
two-cycle engines. Air velocity in the turbocharger blower piping should not
exceed 3300 ft/min (1006 m/min); gas velocity in the exhaust system should
not exceed 6000 ft/min (1828 m/min).The exhaust-gas temperature should
not be reduced below 275°F (135°C), to prevent condensation.
The method presented here is the work of W. M. Kauffman, reported in
Power.

I-C ENGINE ROOM VENT SYSTEM DESIGN

A radiator-cooled 60-kW internal-combustion engine generating set operates
in an area where the maximum summer ambient temperature of the inlet air is
100°F (37.8°C). How much air does this engine need for combustion and for

the radiator? What is the maximum permissible temperature rise of the room
air? How much heat is radiated by the engine-alternator set if the exhaust
pipe is 25 ft (7.6 m) long? What capacity exhaust fan is needed for this
2
engine room if the engine room has two windows with an area of 30 ft (2.8
2
m ) each, and the average height between the air inlet and the outlet is 5 ft
(1.5 m)? Determine the rate of heat dissipation by the windows. The engine is

located at sea level.

Calculation Procedure:

1. Determine engine air-volume needs
Table 4 shows typical air-volume needs for internal-combustion engines