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Intro Thermal Fluid > Quiz 1 > Flashcards

Quiz 1 Flashcards

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1
Q

What are base units? list them

A

mutually independent dimensions
Length [m], mass [kg], time [s], electric current [A],
temperature [K], luminous intensity [cd], amount of
substance [mol]

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2
Q

Difference between thermodynamics, fluid mechanics, and heat transfer?

A

thermo - heat and it’s relation to energy and work
fluid mechanics - fluids and the forces on them
heat transfer - heat exchange between systems

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3
Q

Closed vs open system

A 
Closed systems (control mass) always contain the same matter.
Open systems (control volume) is a given region of space through which mass flows.
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4
Q

What is an isolated system?

A

A special type of closed system that does not interact in any way with its surroundings.

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5
Q

What is a property?

A

A macroscopic characteristic of a system to which a

numerical value can be assigned at a given time.

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6
Q

What are examples of properties?

A

mass, volume, energy, temperature, and pressure

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7
Q

What does state refer to?

A

The condition of a system as described by its properties

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8
Q

What is a process?

A

The transformation from one state to another. When any of the properties of a system changes, the state changes, and the system is said to have undergone a
process.

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9
Q

What is an extensive property?

A

varies with time but not position. It’s value is the sum of its parts (mass, moles, volume, energy)

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10
Q

What is an intensive property?

A

varies with time and position. It is not additive. (density, pressure, temperature, velocity)

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11
Q

What does it mean if a system is in an equilibrium state?

A

intensive properties such as temperature and pressure are uniform within the system

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12
Q

What does it mean if a system is in steady state?

A

Its properties do not change with time

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13
Q

What does it mean if a system is transient?

A

Its properties change with time

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14
Q

What is specific volume?

A

1/p (density)

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15
Q

What does phase refer to?

A

a quantity of matter that is homogeneous throughout in both chemical composition and physical structure

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16
Q

What does homogeneity in physical structure mean?

A

The matter is all solid, all liquid, or all gas

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17
Q

Convert C to K

A

K = C+273.15

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18
Q

Convert F to C

A

C=(F-32)*5/9

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19
Q

What is a pure substance?

A

uniform and invariable in chemical composition; can exist in more than one phase

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20
Q

What is the state principle?

A

From two independent, intensive thermodynamic properties you can determine the thermodynamics state of a pure substance (the other intensive properties)

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21
Q

What is the vapor dome?

A

The dome-shaped region composed of the two phase liquid-vapor states

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22
Q

what is saturation temperature?

A

the temperature at which a phase change takes place at a given pressure

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23
Q

What is saturation pressure?

A

The pressure at which a phase change takes place at a given temperature

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24
Q

What is the critical point?

A

At the top of the dome, where saturated liquid and saturated vapor lines meet

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25
What is critical temperature?
the maximum temperature at which liquid and vapor and phases can coexist in equilibrium
26
What is critical pressure?
The pressure at the critical point
27
Within two phase regions are pressure and temperature independent?
no
28
What is true about an incompressible substance?
``` specific volume is constant density is constant u=u(T) h=u(T)+pv cv=cp =dq/dT u2-u1=c(T2-T1) h2-h1=c(T2-T1)+v(p2-p1) v(p2-p1) is often small U2-U1=mc(T2-T1)=pcV(T2-T1) ```
29
How can energy be transferred to and from a closed system?
Work and heat
30
Work done by the system, positive or negative?
positive
31
Work done on the system, positive or negative?
negative
32
What is power?
dW/dt
33
What is work?
integral of pdV
34
What is the work for a constant volume?
0
35
What is the work for a constant pressure?
P(V2-V1)
36
What is the work for a constant temperature ideal gas?
P1*V1*ln(V2/V1) or P2*V2*ln(V2/V1) or nRT*ln(V2/V1)
37
What is the area under a PV curve?
work
38
What condition is needed for heat transfer?
heat difference between system and surroundings
39
positive Q, heat transfer to or from the system
to the system
40
negative Q, heat transfer to or from the system
from the system
41
What does adiabatic mean?
a process involving no heat transfer with its surroundings
42
What are the modes of energy transfers by heat?
conduction, radiation, convection
43
What is conduction?
The transfer of energy by contact with solid (or a fluid at rest)
44
What is radiation?
energy transported by electromagnetic waves (or photons); can occur in a vacuum
45
What is convection?
transfer of energy by contact with flowing fluids (gas or liquid)
46
equation for rate of heat transfer by conduction | Fourier's law
``` Q'=-kA[(T2-T1)/L] Q': rate of heat transfer going outside k: thermal conductivity A: wall area L: wall thickness T2: outside temperature T1: inside temperature ```
47
equation for rate of heat transfer by radiation (Stefan-Boltzman law)
Q'=epsilon*sigma*A*[Tb^4-Ts^4] Q': rate of heat transfer going to lower temp surface epsilon: emissivity sigma: Stefan-Boltzman constant (5.67*10^-8 W/(m^2*K^4))
48
Heat transfer depends on....
temperature difference and area
49
Change in energy in thermodynamics comes from
kinetic energy, gravitational potential energy, internal energy
50
change in energy or delta E =
delta E = delta U +delta KE + delta PE where U is internal energy or delta E = Q-W
51
What is the first law of thermodynamics?
energy is neither created nor destroyed
52
dE/dt =
Q'-W'
53
What is enthalpy (H)?
H = U + pV
54
What is specific enthalpy (h)?
h = H/m = U/m +pV/m = u+pv
55
What is specific heat (cv) at constant volume?
partial derivative of specific internal energy (u) with respect to temperature (T);
56
What is specific heat (cp) at constant pressure?
partial derivative of specific enthalpy (h) with respect to temperature (T); also cv+R/M
57
Is there any relationship between specific heat (c) and heat (Q)?
no
58
For an ideal gas what does specific internal energy depend on?
only temperature
59
ideal gas law in all forms
pV=nRT | pv=R/M*T (m=nM)
60
specific enthalpy depends on what?
only temperature
61
What is a thermodynamic cycle?
a sequence of processes that begins and ends at the same state
62
What are three examples of a thermodynamic cycle?
power cycle, refrigeration cycle, heat pump cycle
63
What is the power cycle equation?
Wcycle = Qin - Qout Wcycle: net energy transfer by work from the system per cycle of operation, usually in the form of electricity Qin: heat transfer of energy to the system per cycle from the hot body Qout: heat transfer of energy from the system per cycle discharged to atmosphere
64
thermal efficiency equations for a power cycle?
n = Wcycle/Qin = (Qin - Qout) / Qin = 1 - Qout/Qin; must be less than 100%
65
What is the refrigeration or heat pump cycle equation?
Wcycle = Qout - Qin Wcycle: net energy transfer by work to the system per cycle of operation, usually in the form of electricity Qin: heat transfer of energy to the system per cycle from the cold body Qout: heat transfer of energy from the system per cycle to the hot body or surrounding space
66
Coefficient of Performance (COP) (Beta) for refrigeration cycle
Beta = Qin/Wcycle = Qin / (Qout-Qin)
67
Coefficient of Performance (COP) (Gamma) for heat pump cycle
Gamma = Qout/Wcycle = Qout / (Qout-Qin); must be greater than 1; Gamma - Beta = 1

Intro Thermal Fluid (2 decks)

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