Yunus A. Çengel,
University of Nevada, Reno
Michael A. Boles,
North Carolina State University
| Compressor | is a device that increases the pressure of a gas to very high pressures.
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| Conservation of energy principle | or energy balance based on the first law of thermodynamics may be expressed as follows: Energy can be neither created nor destroyed; it can only change forms. The net change (increase or decrease) in the total energy of the system during a process is equal to the difference between the total energy entering and the total energy leaving the system during that process. The energy balance can be written explicitly asEin - Eout =(Qin -Qout ) + (Win -Wout ) + (Emass, in- Emass, out ) = DEsystem
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| Diffuser | is a device that increases the pressure of a fluid by decreasing the fluid velocity.
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| Fan | is a device that increases the pressure of a gas slightly and is mainly used to mobilize a gas.
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| First law of thermodynamics | is simply a statement of the conservation of energy principle, and it asserts that total energy is a thermodynamic property. Joule's experiments indicate the following: For all adiabatic processes between two specified states of a closed system, the net work done is the same regardless of the nature of the closed system and the details of the process.
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| First law of thermodynamics for a closed system | using the classical thermodynamics sign convention is Qnet, in - Wnet, out = DEsystem or Q - W =D E where Q = Qnet, in = Qin - Qout is the net heat input and W = Wnet, out = Wout - Win is the net work output. Obtaining a negative quantity for Q or W simply means that the assumed direction for that quantity is wrong and should be reversed.
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| Heat exchangers | are devices where two moving fluid streams exchange heat without mixing. Heat exchangers are widely used in various industries, and they come in various designs. The simplest form of a heat exchanger is a double-tube (also called tube-and-shell) heat exchanger composed of two concentric pipes of different diameters. One fluid flows in the inner pipe, and the other in the annular space between the two pipes. Heat is transferred from the hot fluid to the cold one through the wall separating them. Sometimes the inner tube makes a couple of turns inside the shell to increase the heat transfer area, and thus the rate of heat transfer.
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| Mixing chamber | is the section of a control volume where mixing process takes place for two or more streams of fluids. The mixing chamber does not have to be a distinct "chamber." Mixing chambers are sometimes classified as direct-contact heat exchangers.
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| Nozzle | is a device that increases the velocity of a fluid at the expense of decreasing pressure.
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| Pump | is a device that increases the pressure of liquids very much as compressors increase the pressure of gases.
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| Stationary systems | are systems that do not involve any changes in their velocity or elevation during a process
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| Steady | means no change with time.
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| Steady-flow process | which was defined in Chapter 1, is a process during which a fluid flows through a control volume steadily.
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| Throttling valves | are any kind of flow-restricting devices that cause a significant pressure drop in the 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 11.
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| Total energy | E of a system is the sum of the numerous forms of energy that can exist within the system such as internal (sensible, latent, chemical, and nuclear), kinetic, potential, electrical, and magnetic.
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| Turbine | is a device that produces shaft work due to a decrease of enthalpy, kinetic, and potential energies of a flowing fluid.
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| Uniform-flow process | involves the following idealization: The fluid flow at any inlet or exit is uniform and steady, and thus the fluid properties do not change with time or position over the cross section of an inlet or exit. If they do change with time, the fluid properties are averaged and treated as constants for the entire process.
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| Unsteady-flow | or transient-flow, processes are processes that involve changes within a control volume with time.
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2002 McGraw-Hill Higher Education