Unformatted text preview: ion)(Unit cost of power)
(0.9837 107 kWh/yr)($0.075/kWh)
$737,800/yr That is, this turbine can save the facility $737,800 a year by simply taking advantage of the potential that is currently being wasted by a throttling valve, and
the engineer who made this observation should be rewarded.
Discussion This example shows the importance of the property entropy since it
enabled us to quantify the work potential that is being wasted. In practice, the
turbine will not be isentropic, and thus the power produced will be less. The
analysis above gave us the upper limit. An actual turbine-generator assembly
can utilize about 80 percent of the potential and produce more than 900 kW of
power while saving the facility more than $600,000 a year.
It can also be shown that the temperature of methane will drop to 113.9 K
(a drop of 1.1 K) during the isentropic expansion process in the turbine instead
of remaining constant at 115 K as would be the case if methane were assumed
to be an incompressible substance. The temperature of...
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