Question

Thermal efficiency of heat engine cycle is defined as

Answer 1

hi


here is your answer

Heat engines turn heat into work. The thermal efficiency expresses the fraction of heat that becomes useful work. The thermal efficiency is represented by the symbol ηη, and can be calculated using the equation:

η=WQHη=WQH

Where:

WW is the useful work and

QHQH is the total heat energy input from the hot source.[2]

Heat engines often operate at around 30% to 50% efficiency, due to practical limitations. It is impossible for heat engines to achieve 100% thermal efficiency (η=1η=1) according to the Second law of thermodynamics. This is impossible because some waste heat is always produced produced in a heat engine, shown in Figure 1 by the QLQL term. Although complete efficiency in a heat engine is impossible, there are many ways to increase a system's overall efficiency.

An Example

If 200 joules of thermal energy as heat is input (QHQH), and the engine does 80 J of work (WW), then the efficiency is 80J/200J, which is 40% efficient.

This same result can be gained by measuring the waste heat of the engine. For example, if 200 J is put into the engine, and observe 120 J of waste heat, then 80 J of work must have been done, giving 40% efficiency.


hope it helps

Answer 2

Thermal efficiency . In thermodynamics , the thermal efficiency ( ) is a dimensionless performance measure of a device that is thermal energy , such as an internal combustion engine, a steam turbine or a steam engine, a boiler, furnace, or a refrigerator for example.


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