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BIEN 300 > Chapter 2: Energy & energy transfer > Flashcards

Chapter 2: Energy & energy transfer Flashcards

1
Q

what can energy cause?

A

it can cause change and work

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2
Q

what are macroscopic forms of energy?

A

those a system possesses as a whole with respect to some outside reference frame, such as kinetic and potential energy

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3
Q

what are microscopic forms of energy?

A

related to the molecular structure of a system and the degree of the molecular activity

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4
Q

what is kinetic energy?

A

the energy a system possesses as a result of its motion relative to some reference frame

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5
Q

what is potential energy?

A

the energy that a system possesses as a result of its elevation in a gravitational field

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6
Q

what is internal energy?

A

Sum of all microscopic forms of energy, it comes from the total kinetic (changes with temperature) and potential energy (changes with state) of molecules which composes the system

Internal = thermal + chemical + nuclear + electric + magnetic

Internal = sensible + latent + chemical + nuclear

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7
Q

what is sensible energy?

A

portion of internal energy of a system associated with the kinetic energies of the molecules

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8
Q

what is latent energy?

A

portion of internal energy associated with the phase of a system

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9
Q

what is chemical energy?

A

portion of internal energy associated with the atomic bonds in a molecule

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10
Q

what is nuclear energy?

A

portion of internal energy associated with the strong bonds within the nucleus of the atom itself

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11
Q

what is thermal energy?

A

thermal = sensible + latent

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12
Q

what is a stationary system?

A

where total energy = total internal energy
since both kinetic and potential energy are equal to zero

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13
Q

what is mechanical energy?

A

form of energy that can be converted to mechanical work completely and directly by an ideal mechanical device, such as an ideal turbine

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14
Q

what is the mechanical flow energy of a flowing fluid?

A

pressure

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15
Q

where does total energy occur when in static form?

A

contained or stored in a system

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16
Q

where does energy interactions occur when in dynamic forms?

A

at the system boundary

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17
Q

what kind of systems can heat transfer occur in?

A

closed and open systems

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18
Q

what kind of systems can work occur in?

A

closed and open systems

19
Q

what kind of systems can mass transfers occur in?

A

open systems only

20
Q

what is heat and when does heat transfer occur?

A

heat is a form of energy that is transferred between 2 systems or between a system and its surrounding when there is a difference in temperature between them
no temperature difference = no heat transfer

21
Q

what is conduction?

A

heat transfer mechanisms that transfers energy from the more energetic particles of a substance to the adjacent less energetic ones as a result of interaction between particles (touching)

22
Q

what is convection?

A

heat transfer mechanism that transfers energy between a solid surface and the adjacent fluid that is in motion.
Involves the combined effects of conduction and fluid motion: the faster the fluid motion the greater the heat transfer

23
Q

what is radiation?

A

heat transfer mechanism that transfers energy due to the emission of electromagnetic waves (or photons)

24
Q

when is energy recognized as heat transfer?

A

only when it crosses the system boundary

25
Q

what is work?

A

the energy transfer associated with a force acting through a distance.
the energy transfer is not due to temperature differences
the work done is proportional to the force applied and the distance traveled.

26
Q

what is mechanical work?

A

work due to the transfer of mechanical energy
work done to raise and/or accelerate a body = change in potential and/or kinetic energy

27
Q

what are the conditions for mechanical work to occur?

A
  1. A force is acting on the boundary of the system
  2. The boundary must move

both conditions need to be met for work to be done

28
Q

what are examples of different forms of mechanical work?

A
  • Shaft work: force acting through a moment arm generates a torque, this forced acts through a distance
  • Spring work: length of spring changes under influence of a force
  • Elastic solid bars work: without permanent deformation, normal stress
  • Stretching of a liquid film work: surface tension
  • work done to raise or accelerate body = related to potential and kinetic energy
29
Q

what is electrical work?

A

non-mechanical form of work where the generalized force is the volt (electric potential) and the generalized displacement is the electrical charge

30
Q

what is magnetic work?

A

non-mechanical form of work where the force is the magnetic field strength and the displacement is the total magnetic dipole moment

31
Q

what is electrical polarization work?

A

non-mechanical form of work where the force is the electrical field strength and displacement is the polarization of the medium

32
Q

What kind of functions are heat and work?

A

path functions, they both are associated with process and their magnitudes depend on the path followed during a process as well as the end states
- they have inexact differentials

33
Q

what kind of functions are properties?

A

point functions, associated with state
- exact differentials

34
Q

difference between energy transfer in a closed vs open system?

A

In a closed system, only heat transfer and work are included in energy transfer
In an open system, energy transfer also include the flow energy in addition to work and heat

35
Q

what is the zeroth law of thermodynamics?

A

If object A is in thermal equilibrium with object B, and object B is in thermal equilibrium with object C, then object C is also in thermal equilibrium with object A

36
Q

what is the first law of thermodynamics?

A

energy can be neither created nor destroyed during a process, it can only change forms
- total energy remains constant

37
Q

what is the sign convention for heat transfer to a system and work done on a system?

A

positive

38
Q

what is the sign convention for heat transfer from a system and work done by a system?

A

negative

39
Q

what does a closed system cycle involve?

A

only heat transfer and work
total energy = 0, so Q = W

40
Q

what is energy efficiency?

A

performance of energy conversion or transfer process
- losses are due to friction or heat
- increased energy efficiency = reduced energy use

41
Q

what is energy efficiency?

A

performance of energy conversion or transfer process
- losses are due to friction or heat
- increased energy efficiency = reduced energy use

42
Q

what is pump and turbine efficiency?

A

the effectiveness of the conversion process between the mechanical work supplied or extracted and the mechanical energy of the fluid

43
Q

what is pump and turbine efficiency?

A

the effectiveness of the conversion process between the mechanical work supplied or extracted and the mechanical energy of the fluid

BIEN 300 (8 decks)

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