# Shared Flashcard Set

## Details

Thermodynamics
Midterm #1
79
Engineering
02/04/2009

Term
 past, present, future
Definition
 time
Term
 extent or size
Definition
 length, area, volume
Term
 inability to move
Definition
 mass
Term
 a pull or push
Definition
 force
Term
 tendency to move at constant speed in a single direction
Definition
 momentum
Term
 ability to “do”
Definition
 energy, work
Term
 rate of “doing”
Definition
 power
Term
 hot, warm, cold
Definition
 temperature
Term
 amount of matter
Definition
 mole
Term
 chaos, uncertainty, disorder
Definition
 entropy
Term
 maximum work potential
Definition
 exergy, availability
Term
 SI Primary quantity
Definition
 • time second (s) • length meter (m) • mass kilogram (kg) • amount of matter mole (mol) • temperature kelvin (K)
Term
 1 second
Definition
 the time required for a beam of cesium-133 atoms to resonate 9,192,631,770 cycles in a cesium resonator
Term
 1 meter
Definition
 the length of the path traveled by light in a vacuum during a time interval of one second. The agreed upon speed of light is 299,792,458 m/s
Term
 1 kilogram
Definition
 the mass of a certain platimun-irridium cylinder maintained under prescribed conditions at the International Bureau of Weights and Measures in Paris, France
Term
 1 mole
Definition
 the amount of substance containing as many elementary entities as there are atoms in 0.012 kg of carbon-12. These elementary entities must be specified, and may be atoms, molecules, electrons, ions or other particles or specific groups.
Term
 Secondary quantity
Definition
 • velocity distance/time m/s • acceleration velocity/time m/s2 • force mass x acceleration kg⋅m/s2 newton (N) • work force x distance N⋅m joule (J) • power work/time J/s watt (W) • pressure force/area N/m2 pascal (Pa)
Term
 In the English system of units (blank) is a primary quantity
Definition
 force; The standard pound-force is the force with which 1 pound-mass (lbm) is attracted to the earth when the standard pound-mass is suspended in the earth’s gravitational field at a position where the acceleration due to gravity is 32.1740 ft/s2.
Term
 F = kNMa
Definition
 Newton’s law
Term
 kN
Definition
 Newton’s constant
Term
 F = kGM1⋅ M2/r2
Definition
 law of gravitational attraction
Term
 kG, the universal gravitational constant
Definition
 6.67 x 10-11 m3/kg⋅ s2
Term
 thermodynamic system
Definition
 a quantity of matter or a region of space enclosing a device or a combination of devices containing a quantity of matter that is selected for study. The mass or region outside the system is called the surroundings or the environment. The real or imaginary surface that separates the system from its environment is called the boundary or control surface, which is of zero thickness (and consequently, has no mass). A system is either closed or open.
Term
 closed system
Definition
 No mass crosses the boundary of a closed system. Energy can be transferred across the system boundary, which may be fixed or movable. ex. The mass contained within a piston-cylinder device has both fixed and movable boundaries.
Term
 open system
Definition
 control volumeMass as well as energy can cross the boundary of an open system. The boundary can be fixed or movable and can be either real or imaginary.
Term
 isolated system
Definition
 A thermodynamic system that has no mass or energy crossing its boundaries (i.e., a system that does not communicate with its surroundings) An isolated system consists of a fixed amount of mass and contains the same amount of energy at all times.
Term
 property
Definition
 Any characteristic of a system is called a property. Some of the familiar thermodynamic properties of a control mass include its mass (M), volume (V), temperature (T), pressure (P), and density (ρ). The total energy (E) of a control mass is also a property.
Term
 Extensive properties
Definition
 masslengthvolumeentropyenthalpyenergyelectrical resistancetexturestiffnessparticle numberconcentration
Term
 Intensive properties
Definition
 temperaturechemical potentialdensityviscosityvelocityelectrical resistivityspectral absorption maxima (in solution)specific energyspecific heat capacitylustrehardnessmelting point and boiling pointpressurebuoyancy[citation needed]ductilityelasticitymalleabilitymagnetismodorstate
Term
 specific properties
Definition
 Extensive properties per unit mass
Term
 state
Definition
 At any instant of time, a system is described by the values of its properties. The condition of a system as described by its properties
Term
 equilibrium
Definition
 Equilibrium states have no unbalanced potentials. The temperature, pressure and composition are uniform within the system and there is no mass transport between any phases within the system. An equilibrium state is a state in thermal, mechanical, chemical, and phase equilibrium.
Term
 process
Definition
 When the state of a system is changed (i.e., when one or more of the properties of a system changes), the system is said to have undergone a process
Term
 process path
Definition
 The process path is defined by the states that the system passes through in transition from some initial state to some final state. If the initial and final states are the same, the system is said to have gone through a cycle.
Term
 isobaric
Definition
 A process that occurs at constant pressure
Term
 isothermal
Definition
 A process that occurs at constant temperature
Term
 isochoric
Definition
 a process that occurs at constant volume
Term
 Production Bookkeeping
Definition
 Production(X) = Outflow(X) – Inflow(X) + Accumulation(X)
Term
 Production Bookkeeping (rate basis)
Definition
 Rate of production(X) = Rate of outflow(X) – Rate of inflow(X) + Rate of accumulation(X)
Term
Definition
 When the rate of accumulation is zero (dX/dt = 0)
Term
Definition
 If a device operates for long periods of time at the same conditions and the inlet and outlet flow rates are fixed
Term
 conserved quantities
Definition
 Production(X) = 0 and Rate of production(X) = 0Mass, momentum and energyWe cannot prove that they are conserved quantities. We have not been able to identify any system, however, to show that these quantities are not conserved.
Term
 1/2 MV2
Definition
 Kinetic energy
Term
 work
Definition
 If a force is applied to an object and the object changes position, then work has been done on the object. If the object does not move, no work was done as a result of the applied force. The total amount of work done depends upon how the force was applied over the displacement (i.e., the total work depends upon how the force varies with position). We say that work depends on the process path as well as on the end points. Work is a path function.
Term
 Weight
Definition
 the gravitational force applied to a body. The weight of an object on earth is the force exerted by the planet Earth on the object. At sea level, g = 9.807 m/s2.
Term
 Mgz
Definition
 Potential energy is the energy that a system possesses as a result of its elevation in a gravitational field.
Term
 Macroscopic energy modes
Definition
 kinetic energy and potential energy
Term
 Microscopic energy modes
Definition
 kinetic energies of the molecules (translation, rotational, vibrational energies); nuclear energy (electron translation, electron spin, nuclear spin, nuclear binding forces); intermolecular binding forces (latent energies); bond energy; magnetic and electric dipole moments, etc.
Term
 internal energy
Definition
 U ≡ internal energy = sum of microscopic energy forms
Term
 total energy (E)
Definition
 The total energy (E) of a system is the sum of its microscopic and macroscopic energy formsE=U+KE+PE
Term
 Energy Hypothesis
Definition
 Matter can be treated as having a property called energy, which is an extensive, conserved scalar measuring its ability to cause change. Work is energy transfer, i.e.,work is energy being transferred.
Term
 Heat
Definition
 The form of energy that is transferred between two systems (or say, a system and its environment) by virtue of a temperature difference. The transfer occurs on the molecular level. The direction of heat transfer is always from the hotter entity to the cooler. Once temperature equality is established, the heat transfer stops.
Term
 three mechanisms for heat transport
Definition
Term
 Conduction
Definition
 the transfer of energy by molecular collisions
Term
Definition
 transfer of energy via electromagnetic waves
Term
Definition
 any process in which no energy transfer as heat occurs across the boundary of the system. surface
Term
 work of expansion
Definition
 the work that a control mass (the system) transfers to its boundary as it expands. The force exerted on the boundary is the pressure times the area. If the control mass expands a differential amount dV, then the incremental amount of work done by the control mass on its boundary during this volume change is δWexpansion = PdV, dV > 0 The work is transferred across the system boundary to the surroundings.
Term
 work of compression
Definition
 The work transferred to a control mass (the system) that is being compressedIf the control mass is compressed and the volume decreases a differential amount dV, then the incremental amount of work done on the control mass by its boundary during this compression process is δWcompression = - PdV, dV < 0
Term
 electrical work
Definition
 Electrons can cross the system boundary thereby transferring work to the control mass. The electrical work can be expressed on a rate basis as Welectric =VI W is the electric power (in watt), V is the voltage
Term
 Shaft work
Definition
 energy transfer due to a rotating shaft. Shaft work is proportional to the applied torque T and the number of rotations n of the shaft: Wshaft = F s=2πnT
Term
 state postulate
Definition
 There are as many independent thermodynamic properties as there are independent ways of changing the energy of the control mass of interest.
Term
 simple compressible substances
Definition
 substances for which the only work mode is through volume change, via compression and expansion processes
Term
 “How many thermodynamic properties must be specified in order to completely fix the thermodynamic state of a control mass?”
Definition
 Since the energy of a simple compressible substance can be changed only via the transfer of energy as heat and the transfer of energy as PdV work (work due to volume change), specification of any two independent intensive thermodynamic properties completely fixes the state.
Term
 phase
Definition
 a form of a substance that has a distinct molecular structure that is homogenous throughout and separated from other phases by identifiable boundaries.
Term
 latent heat
Definition
 The amount of energy needed to cause a phase change
Term
 latent heat of fusion
Definition
 The amount of energy absorbed by a solid as it melts (changes from solid to liquid)
Term
 latent heat of vaporization
Definition
 The amount of energy absorbed by a liquid as it evaporates (changes from liquid to gas)
Term
 latent heat of sublimation
Definition
 The amount of energy absorbed by a solid as it sublimes (changes from solid to gas)
Term
 quality
Definition
 a property that only has meaning for the two-phase mixture, is used to give the relative amounts of vapor and liquid.
Term
 enthalpy
Definition
 H = U + PV andh = u + Pv
Term
 ideal gas equation
Definition
 Pv = RTPV=MRTPV = NˆRuT
Term
 universal gas constant
Definition
 8.314 kJ/kmol ⋅K
Term
 specific heat ratio k
Definition
 k = cp/cv - for monatomic gases, k ≈ 1.667 for all temperatures - for diatomic gases k ~ 1.4 for temperature near 298 K
Term
 ideal liquid
Definition
 a liquid for which at fixed temperature, specific volume changes with pressure are negligible. For an ideal liquid, specific volume varies solely with temperature. k = cp/cv = 1
Term
 coefficient of performance
Definition
 COP=desired quantity / required quantity
Term
 Flow work
Definition
 the work required to push a fluid across a boundary of a control volume. necessary for maintaining a continuous flow through a control volume.
Term
 mass flow rate
Definition
 m(dot) =ρVA
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