Modern Engineering Thermodynamics

360 CHAPTER 10: Availability Analysis
temperature of a Westinghouse 50.0 W incandescent lightbulb
is 50.0°C. Tom asks you to determine the steady state
irreversibility rate of each lightbulb when the local
environmental temperature is 20.0°C and comment on why
the Westinghouse bulb is more efficient. Write and solve a
thermodynamics problem that answers these questions.
99.* As a chief engineer at the local fire station, you are asked to use
one of your fire hoses to fill a large swimming pool. The hose
will be laid on the ground and the water will exit at 3.50 m/s at
18.0°C. Before you can respond to this request, you need to
know the specific flow availability at the exit of the hose when
the local environment is at 0.101 MPa and 20.0°C. Write and
solve a thermodynamics problem that answers this question.
100.* You received a promotion to production engineer at a foodprocessing
factory. A particularly critical process involves the
mixing of ingredients with warm water in a large insulated vat.
The vat’s drain is kept open, so water must be continuously
added to maintain the proper mix. The water comes from a
hot water source at 38.0°C at 3.10 kg/s and a cold water
source at 15.0°C at 2.50 kg/s. The local environment is at
0.101 MPa and 20.0°C. To keep control of this process, you
need to know the temperature of the mixed water in the tub
and the second law availability efficiency of the tub as a
mixing-type heat exchanger. Write and solve a
thermodynamics problem that provides the answers to these
questions.