Glossary
to accompany
Thermodynamics: An Engineering Approach, 5th edition
by Yunus A. Çengel and Michael A. Boles50Thermoelectric circuit is a circuit that incorporates both thermal and electrical effects.
Thermoelectric generator uses the Seebeck effect as the basis for thermoelectric power
generation.
Thermoelectric refrigerator is a refrigerator using electric energy to directly produce
cooling without involving any refrigerants and moving parts.
Thermo-mechanical exergy is the exergy associated with the conversion of thermal
energy to mechanical energy and disregards any mixing and chemical reactions.
Third law of thermodynamics states that the entropy of a pure crystalline substance at
absolute zero temperature is zero.
Throat is the smallest flow area of a converging-diverging nozzle.
Throttling valves are any kind of flow-restricting devices that cause a significant
pressure drop in a flowing fluid. Some familiar examples are ordinary adjustable valves,
capillary tubes, and porous plugs. Unlike turbines, they produce a pressure drop without
involving any work. The pressure drop in the fluid is often accompanied by a large drop
in temperature, and for that reason throttling devices are commonly used in refrigeration
and air-conditioning applications. The magnitude of the temperature drop (or, sometimes,
the temperature rise) during a throttling process is governed by a property called the
Joule-Thomson coefficient, which is discussed in Chapter 12.
Thrust is the unbalanced force developed in a turbojet engine that is caused by the
difference in the momentum of the low-velocity air entering the engine and the high-
velocity exhaust gases leaving the engine, and it is determined from Newton’s second
law.
Ton of refrigeration is the capacity of a refrigeration system equivalent to the energy
that can freeze 1 ton (2000 lbm) of liquid water at 0°C (32°F) into ice at 0°C in 24 h.
One ton of refrigeration is equivalent to 211 kJ/min or 200 Btu/min (12,000 Btu/h). The
cooling load of a typical 200-m
2
(2153-ft2
) residence is in the 3-ton (10-kW) range.Top dead center TDC is the position of the piston when it forms the smallest volume in
the cylinder.
Topping cycle is a power cycle operating at high average temperatures that rejects heat
to a power cycle operating at lower average temperatures.
Total differential of a dependent variable in terms of its partial derivatives with respect
to the independent variables is expressed as, for z = z (x, y),