Second Law of Thermodynamics

Second Law of Thermodynamics

Heat Engine & Reversed Heat Engine

What is 2nd Law of Thermodynamics??

"Although the nett heat supply in cycle is equal to the nett work done, gross heat supply mst be always greater than work done"

Thermal Energy Reservoir

• Heat sink:Reservoir that absorbs heat

• Heat source:Reservoir that supllies heat

Heat engine

• device that uses heat to perform work

• application example: power plant, gas turbine, locomotive engine, steam engine

Reversed Heat Engine

• Device that make heat flows from cold to hot

• application example: refrigeration, air conditioning, heat pump

The difference between heat pump and air conditioning

or refrigerator

• Desire output for heat pump is Q_H

• Desire output for air conditioning/refrigerator is Q_L

How to measure performance for heat engine and heat pump??

• heat engine: efficiency

• reversed heat engine: coefficient of performance