(See related pages)
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| 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. |
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| Average velocity | is the average value of the normal velocity across an entire flow cross section and if the velocity were the average velocity all through the cross section, the mass flow rate would be identical to that obtained by integrating the actual velocity profile. |
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| Compressor | is a device that increases the pressure of a gas to very high pressures (typical pressure ratios are greater than 3). |
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| Continuity equation | is the conservation of mass equation as it is often referred to in fluid mechanics. |
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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 as |
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| Conservation of mass principle | is expressed as net mass transfer to or from a control volume during a time interval that is equal to the net change (increase or decrease) in the total mass within the control volume during the time interval. |
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| Convected energy | (see flow work). |
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| Diffuser | is a device that increases the pressure of a fluid by decreasing the fluid velocity. |
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| Energy transport by mass | is the product of the mass of the flowing fluid and its total energy. The rate of energy transport by mass is the product of the mass flow rate and the total energy of the flow. |
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| Fan | is a device that increases the pressure of a gas slightly (typical pressure ratios are less than 3) 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 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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| Flow energy | (see flow work). |
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| Flow work | is work required to push mass into or out of control volumes. On a unit mass basis this energy is equivalent to the product of the pressure and specific volume of the mass Pv. |
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| Formal sign convention | (classical thermodynamics sign convention) for heat and work interactions is as follows: heat transfer to a system and work done by a system are positive; heat transfer from a system and work done on a system are negative. |
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| Heat | is defined as the form of energy that is transferred between two systems (or a system and its surroundings) by virtue of a temperature difference. |
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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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| Incompressible substances | such as liquids and solids, these have densities that have negligible variation with pressure. |
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| Mass flow rate | is the amount of mass flowing through a cross section per unit time. |
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| Mixing chamber | is the section of a control volume where the 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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| Pressure ratio | is the ratio of final pressure to initial pressure for a fluid flowing through a compressor. |
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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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| Rate of heat transfer | is the amount of heat transferred per unit time. |
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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 conservation of mass | states that the total rate of mass entering a control volume is equal to the total rate of mass leaving it. |
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| Steady-flow process | is a process during which a fluid flows through a control volume steadily. That is, the fluid properties can change from point to point within the control volume, but at any point, they remain constant during the entire process. During a steady-flow process, no intensive or extensive properties within the control volume change with time. |
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| 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. |
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| Total energy | Eof 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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| Total energy of a flowing fluid | is the sum of the enthalpy, kinetic, and potential energies of the flowing fluid. |
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| Transport energy | (see flow work). |
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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 | also called transient-flow; are processes that involve changes within a control volume with time. |
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| Volume flow rate | is the volume of the fluid flowing through a cross section per unit of time. |
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| Work | is the energy transfer associated with a force acting through a distance. |