Page 416 - Handbook of Energy Engineering Calculations

3
3
ft /min (0.28 m /min).
3
Air entering with the cooling water varies from about 2 ft /min per 1000
3
3
gal/min of 100°F (0.06 m /min per 3785 L/min of 37.8°C) water to 4 ft /min
3
per 1000 gal/min at 35°F (0.11 m /min per 3785 L/min at 1.7°C). Using a
3
3
value of 3 ft /min (0.08 m /min) for this condenser, we see the quantity of air
3
that must be handled is (ft /min per 1000 gal/min)(cooling-water flow rate,
3
3
gal/min)(1000, or ft /min of air = (3)(13,000/1000) = 39 ft /min at 60°F (1.1
3
3
3
m /min at 15.6°C). At 80°F (26.7°C) ft /min = (3) (30,000/1000) = 90 ft /min
3
(2.6 m /min).
3
Hence, the total air quantity that must be handled is 39 + 10 = 49 ft /min
3
3
(1.4 m /min) with 60°F (15.6°C) cooling water, and 90 + 10 = 100 ft /min
3
(2.8 m /min) with 80°F (26.7°C) cooling water. The air is usually removed
from the barometric condenser by a two-stage air ejector.

Related Calculations. For help in specifying conditions for parallel-flow and
counterflow barometric condensers, refer to Standards of Heat Exchange
Institute—Barometric and Low-Level Jet Condensers. Whereas Fig. 6 can be

used for a first approximation of the cooling water required for parallel-flow
barometric condensers, the results obtained will not be as accurate as for
counterflow condensers.

FINNED-TUBE HEAT-EXCHANGER SELECTION

Choose a finned-tube heat exchanger for a 1000-hp (746-kW) four-cycle
turbocharged diesel engine having oil-cooled pistons and a cooled exhaust

manifold. The heal exchanger will be used only for jacket-water cooling.

Calculation Procedure:

1. Determine the heat-exchanger cooling load
The Diesel Engine Manufacturers Association (DEMA) tabulation, Table 3,
lists the heat rejection to the cooling system by various types of diesel
engines. Table 3 shows that the heat rejection from the jacket water of a four-

cycle turbocharged engine having oil-cooled pistons and a cooled manifold is