Entropy in the Real World: Engines. A heat engine , or more simply, an engine , is a device that extracts energy from its environment in the form of heat and does useful work. At the heart of every engine is a working substance .
A heat engine, or more simply, an engine, is a device that extracts energy from its environment in the form of heat and does useful work.
At the heart of every engine is a working substance.
Steam engine Water, in both its vapor and its liquid form.
Automobile engine Gasoline–Air mixture.
A Carnot Engine or Ideal Engine:
In an ideal engine, all processes are reversible and no wasteful energy transfers occur due to, say, friction and turbulence.
A refrigerator is a device that uses work to transfer energy from a low-temperature reservoir to a high-temperature reservoir as the device continuously repeats a set series of thermodynamic processes. In a household refrigerator, for example, work is done by an electrical compressor to transfer energy from the food storage compartment (a low-temperature reservoir) to the room (a high-temperature reservoir).
Figure 20-27 shows a reversible cycle through which 1.00 mol of a monatomic ideal gas is taken. Assume that p = 2p0, V = 2V0, p0 = 1.01 × 105 Pa, and V0 = 0.0225 m3. Calculate (a) the work done during the cycle, (b) the energy added as heat during stroke abc, and (c) the efficiency of the cycle. (d) What is the efficiency of a Carnot engine operating between the highest and lowest temperatures that occur in the cycle? (e) Is this greater than or less than the efficiency calculated in (c)?