From EIT Mechanical Review: For the Discipline Specific Fundamentals of Engineering Exam, Second Edition
Overview
The conversion of energy to useful power constitutes a major portion of the endeavors of the Mechanical Engineering profession. Energy is available in many forms of organic fuels including coal, oil, natural gas, wood and peat moss. In addition, energy is available from other sources such as ocean water in the form of tides and temperature differentials due to ocean currents, water flowing in rivers, the sun, nuclear reactors, underground thermal sources, to mention a few. The major types of conversion systems include internal combustion engines, gas and vapor turbines, hydroelectric turbine systems and reciprocating steam engines.
The largest amount of energy conversion is done in the many electric generating facilities throughout the United States and the world. The energy is produced by electric generators which are powered by prime movers. Other things being equal, these systems are selected generally on the basis of their thermal efficiency. Probably the best definition of thermal efficiency is:
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? th = (Energy wanted )/(Energy that costs $)
Normally this equation then is written in terms of output power in kw divided by the input energy in kJ/s.
Q:
A power plant for a small company produces 54 kW of useful electric power. The generator has an efficiency of 96% and the pump which is used to circulate the fluid takes 2.5 kW. The heat source supplies 10.2 MJ/min of energy to the system. Determine:
Power output of the heat engine
Thermal efficiency of the power plant
Amount of rejected...
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