Page 390 - Handbook of Energy Engineering Calculations

FIGURE 2 Schematic of a closed-cycle OTEC power plant.

The working fluid may be ammonia, propane, or a Freon. The operating

(saturation) pressures of such fluids at the boiler and condenser temperatures
are much higher than those of water, being roughly 10 bar at the boiler, and
their specific volumes are much lower, being comparable to those of steam in
conventional power plants.

Such pressures and specific volumes result in turbines that are much
smaller and hence less costly than those that use the low-pressure steam of
the open cycle. The closed cycle also avoids the problems of the evaporator.
It, however, requires the use of very large heat exchangers (boiler and

condenser) because, for an efficiency of about 2 percent, the amounts of heat
added and rejected are 50 times the output of the plant. In addition, the
temperature differences in the boiler and condenser must be kept as low as
possible to allow for the maximum possible temperature difference across the

turbine, which also contributes to the large surfaces of these units.
This calculation procedure is the work of M. M. El-Wakil given in his
excellent text, Powerplant Technology, McGraw-Hill, 1984 and 2002. The
reader should refer to that text for further insight into energy calculations,

along with the derivation of the equations given here. The handbook editor
added minor transitional wording to adapt the procedure to the format used in
the handbook.

WAVE CALCULATIONS FOR CHARACTERISTICS AND