Page 230 - Handbook of Energy Engineering Calculations

(0.68)] = 4.1 hp (3.1 kW). A 5-hp (3.7-kW) motor would be chosen to drive
this pump.

Related Calculations. Use this method for any reciprocating diesel engine,
two- or four-cycle. Lube-oil pump capacity is generally selected 10 to 15
percent oversize to allow for bearing wear in the engine and wear of the

pump moving parts. Always check the selected capacity with the engine
builder. Where a bypass-type lube-oil system is used, be sure to have a pump
of sufficient capacity to handle both the engine and cooler oil flow.
Raw-water pumps are generally duplicates of the jacket-water pump,

having the same capacity and head ratings. Then the raw-water pump can
serve as a standby jacket-water pump, if necessary.

CHOICE OF LUBE-OIL COOLER FOR I-C ENGINES

A 500-hp (373-kW) internal-combustion engine rejects 300 to 600 Btu/(bhp ·
h) (118 to 236 W/kWh) to the lubricating oil. What capacity and type of lube-
oil cooler should be used for this engine if 10 percent of the oil is bypassed?

If this engine consumes 2 gal (7.6 L) of lube oil per 24 hours at full load,
determine its lube-oil consumption rate.

Calculation Procedure:

1. Determine the required lube-oil cooler capacity
Base the cooler capacity on the maximum heat rejection rate plus an
allowance for overloads. The usual overload allowance is 10 percent of the

full-load rating for periods of not more than 2 hours in any 24-hour period.
For this engine, the maximum output with a 10 percent overload is 500 +
(0.10)(500) = 550 hp (410 kW). Thus, the maximum heat rejection to the lube

oil would be (500 hp)[600 Btu/(bhp · h)] = 330,000 Btu/h (96.7 kW).

2. Choose the type and capacity of lube-oil cooler
Choose a shell-and-tube type heat exchanger to serve this engine. Long
experience with many types of internal-combustion engines shows that the
shell-and-tube heat exchanger is well suited for lubeoil cooling.