Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Building Science > Principles of Energy > Flashcards

Principles of Energy Flashcards

(67 cards)

Start Studying
1
Q

What is energy?

A

A measurable quantity of heat, work, or light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the only two significant sources of energy?

A

Sun, nuclear material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What’s potential energy?

A

Stored energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What’s kinetic energy?

A

Energy in transition or motion changing from one type of energy to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Doing work requires two things:

A

Converting potential energy to kinetic, Transporting the energy to where its needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What’s the easiest form of energy to move?

A

Electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What’s the most difficult form of energy to move?

A

Mechanical energy because of huge losses due to friction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What’s the first law of thermodynamics?

A

Energy is neither created nor destroyed

Energy transfers and changes forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What’s the second law of thermodynamics?

A

In any system, heat always moves from high temperature to low temperature, unless there is some other external source of energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What’s temperature?

A

A measure of the kinetic energy, or molecular movement, within an object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is heat?

A

The flow of thermal energy between two objects whenever there is a temperature difference between them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is enthalpy?

A

The internal heat of an object, measured in BTUs per pound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What’s a BTU?

A

A measurement of heat. 1 BTU = the heat required to raise 1 pound of water 1 degree F.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What’s specific heat?

A

Number of BTU’s that one pound of any material will absorb for each degree F of temperature change.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What’s the specific heat of water?

A

1 BTU/lb?/degreeF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is sensible heat?

A

Heat that causes a temperature change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is latent heat?

A

Heat that causes a change of state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What type of heat can transfer more energy?

A

Latent heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe steam heating.

A

Water is vaporized (absorbs latent heat)

Steam is condensed (releases latent heat)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe air conditioning.

A

Refrigerant is vaporized (absorbs LH)

Refrigerant is condensed (releases latent heat)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is power?

A

The rate at which work is done or energy is released, measuring the capacity to do work. Measured in Watts, HP, BTUH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is energy?

A

The amount of work that gets done in a given timeframe. Energy has a time component.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Energy =

A

Power x Time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Heat, electricity, and fluids flow when 2 things occur:

A

An open path allows their flow
There is a pressure difference.
Heat: path = molecules, pressure = temp difference
Electricity: path = wires, pressure = voltage
Water: path = pipe, pressure = height difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Fluids flow from...
high pressure to low pressure
26
When pressure equalizes, flow will ______.
stop
27
What are three types of flow paths?
Conductor - allows rapid flow Resistor - flow occurs slowly Barrier - flow is stopped or negligible
28
Heat flows in what three ways?
Conduction, convection, radiation
29
What is conduction?
Heat flow through solids, between adjacent molecules of objects in contact with one another
30
Conductance, or K-value, measures what?
The rate of heat transfer through materials
31
What is convection?
The transfer of heat through moving fluid (typically air or water)
32
What is radiation?
The transfer of heat through space from one object to another
33
All types of radiant energy are categorized by what?
The electromagnetic spectrum
34
Solar energy consists of...
``` UV (5%) Visible light (46%) Infrared heat (49%) ```
35
When solar radiation strikes an object, 1 of 3 things occurs:
Reflectance, absorbance, or transmittance
36
What are the only common substances that reflect both solar and infrared radiation?
Polished aluminum, steel, tin, silver, nickel
37
What's the only common material that transmits most solar radiation?
Glass
38
Glass creates a greenhouse effect because it...
transmits solar radiation but absorbs earthly infrared
39
Emittance or Emissivity measures...
a material's characteristic ability to emit radiant energy. Emittance of 1 is a theoretically perfect emitter. Most materials have emittances of 85% to 95%.
40
What are Low-E coatings?
Metallic coatings that are placed on glass in order to reduce solar transmittance by reflecting most radiation and to reduce the flow of radiant heat from outside to inside (or opposite depending on climate) by decreasing the emissivity of the glass.
41
What is comfort?
Being in thermal equilibrium with the environment without having to sweat or shiver.
42
What conditions determine outdoor comfort?
Temperature, humidity, solar radiation, precipitation, wind
43
ASHRAE 55 defines the factors of indoor comfort:
Air temp, radiant temp, relative humidity, air movement (metabolic rate, clothing - uncontrolled)
44
What's the primary factor in indoor comfort?
Air temperature
45
What are ASHRAE's indoor design temperatures?
70 degrees F in winter | 75 in summer
46
What is ASHRAE's heating balance point temperature?
65 degrees F - the outdoor temp above which no heating is needed to maintain 70 indoors. Sun and heat sources make up difference. Heat gain and heat loss are in balance.
47
What's a Heating degree-day?
A unit to describe how long the temp is below 65 degrees and are thus used to determine the intensity of a heating season.
48
How do you calculate HDDs?
1. Calculate avg temp 2. Subtract it from balance point (65) Answer is the HDD for that day. The HDD From every day are added together to obtain the yearly HDD total.
49
What's the cooling balance point?
The outdoor temp below which no indoor cooling is needed to maintain 75 indoors. The default is 65 degrees.
50
What's a cooling degree-day?
A unit to describe how long the temp is above 65 and are thus used to determine the intensity of a cooling season.
51
How are CDDs calculated?
1. Calculate avg temp 2. Subtract it from the balance point and remove negative Number gives CDD for that day.
52
Why are CDDs less reliable than HDDs as a predictor of cooling costs?
Cooling is more complicated due to other factors of summer comfort: relative humidity, solar gain or shade, internal loads
53
Homes with poor insulation, air leaks, and single-pane windows will have ______ interior surfaces.
colder
54
Well-insulated and air-sealed homes maintain _____ interior surfaces, contributing to better comfort.
warmer
55
Relative humidity is determined by 2 things:
Absolute amount of water vapor in the air | Temperature of the air
56
_____ air can hold more moisture than _______ air.
Warmer, colder
57
As air cools, its relative humidity _______.
increases
58
100% relative humidity indicates that the air is at its ________, or is completely saturated with water. Rain (or condensation) will occur.
dew point
59
Dew points above ___ degrees are considered uncomfortable.
68 degrees F
60
Does humidity affect heat flow?
No, there is no energy advantage to inside humidity in winter.
61
Indoor relative humidity guidelines:
62
In summer, ceiling fans are only effective if:
You can feel the moving air | The thermostat is turned up considerably
63
What is psychrometrics?
The science of air and its properties related to buildings and comfort
64
A psychrometric chart is used to understand human comfort and the energy required to produce it. Each state point on the chart has values for:
``` Dry bulb temp Wet bulb or dew point temp Enthalpy Relative humidity Absolute humidity ```
65
What is enthalpy?
The total energy of the air measured in BTU/lb. Enthalpy is sensible heat + latent heat.
66
What is relative humidity?
The ratio, in percent, between the actual water vapor in the air vs what the air can hold at that temperature.
67
What is absolute humidity?
The actual amount of water in air, measured in grains of water vapor per pound of dry air.

Building Science (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions