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Thermodynamics Definitions

Adiabatic process is a process during which there is no heat transfer. The word
adiabatic comes from the Greek word adiabatos, which means not to be passed.

Air conditioners are refrigerators whose refrigerated space is a room or a building
instead of the food compartment.

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Bar is the unit of pressure equal to 10 Pascal.

Barometer is a device that measures the atmospheric pressure; thus, the atmospheric
pressure is often referred to as the barometric pressure.

Boiler is basically a large heat exchanger where the heat originating from combustion
gases, nuclear reactors, or other sources is transferred to the water essentially at constant
pressure.

Boiling is the phase change process that occurs at the solid–liquid interface when a
liquid is brought into contact with a surface maintained at a temperature sufficiently
above the saturation temperature of the liquid.

Boundary is the real or imaginary surface that separates the system from its
surroundings. The boundary of a system can be fixed or movable.

Boundary work (PdV work) is the work associated with the expansion or compression
of a gas in a piston-cylinder device. Boundary work is the area under the process curve
on a P-V diagram equal, in magnitude, to the work done during a quasi-equilibrium
expansion or compression process of a closed system.

Calorie (cal) is the amount of energy in the metric system needed to raise the
temperature of 1 g of water at 15 °C by 1°C.

Carnot cycle was first proposed in 1824 by French engineer Sadi Carnot. It is
composed of four reversible processes—two isothermal and two adiabatic, and can be
executed either in a closed or a steady-flow system.

Carnot efficiency is the highest efficiency a heat engine can have when operating
between the two thermal energy reservoirs at temperatures T 2 and T 1.
η th = 1 – T 2 / T 1

Carnot heat engine is the theoretical heat engine that operates on the Carnot cycle.

Carnot principles are two conclusions that pertain to the thermal efficiency of reversible
and irreversible (i.e., actual) heat engines and are expressed as follows:

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