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building environmental systems > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

What percentage of our time is spent indoors?

A

87%

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2
Q

Residential and commercial buildings account for __ of total US energy consumption

A

40%

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3
Q

Buildings are the cause of ______ of US greenhouse gas emissions

A

34%

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4
Q

Is energy a rate or quantity?

A

Quantity

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5
Q

What is power?

A

Rate at which energy is transferred

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6
Q

Energy =

A

Power x time

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7
Q

Power =

A

Energy / time

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8
Q

Units of energy

A

Watt-hr
Btu

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9
Q

Units of power

A

Watts
Btuh

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10
Q

When dealing with energy and power, this equation can be used:

A

Q = MCΔT

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11
Q

Electricity converts to:

A

Mechanical energy
Light
Heat

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12
Q

Primary energy

A

Site energy plus energy consumed during production and transportation

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13
Q

Site energy

A

Energy directly used by consumers

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14
Q

What is 1 Btu?

A

heat required to raise 1lb of water by 1 F

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15
Q

What is thermal comfort?

A

Condition of mind that expresses satisfaction with the thermal environment

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16
Q

What influences thermal comfort?

A

Weather
Ventilation
Clothing
A/C
Level of Exhaustion

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17
Q

Two types of heat losses:

A

Conduction
Convection

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18
Q

What are some occupant-related factors that make someone feel “thermally comfortable”?

A

Clothes
Age
Gender
Energy Levels

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19
Q

What are some environmental factors that make someone feel “thermally comfortable” in a building?

A

Weather
Humidity
Proximity of fans
materials used

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20
Q

Moist air is:

A

Dry air + Water vapor

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21
Q

Psychrometry

A

Study of gas-vapor mixtures

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22
Q

What is humidity ratio?

A

Ratio of water vapor to dry air

23
Q

What is relative humidity?

A

Ratio of current humidity to when air is fully saturated

24
Q

Humidity ratio (ω) equation:

A

(M)v / (M)dry air
Mass of water vapor / mass of dry air

25
Q

What is dew point?

A

Defined temperature at which condensation happens

26
Q

At dew point temperature, relative humidity is:

A

100%

27
Q

Wet bulb temperature is _______ than dry bulb temperature

A

Lower

28
Q

Why is WBT lower than DBT?

A

Evaporating moisture removes heat

29
Q

As relative humidity gets closer to 100%, WBT gets __________ DBT.

A

closer to

30
Q

Enthalpy equation

A

Sensible + Latent

31
Q

What is sensible heat?

A

energy needed to raise the temperature of a substance

32
Q

What is latent heat?

A

energy needed for phase change

33
Q

What is sensible heat measured through?

A

DBT

34
Q

What is latent heat measured through?

A

Humidity ratio

35
Q

What are the units of Q?

A

Btu

36
Q

Heating load is:

A

How much heat is lost and needs to be made up

37
Q

Cooling load is:

A

How much heat is gained and must be removed

38
Q

Heat transfer happens in conduction:

A

With Physical contact

39
Q

Heat transfer happens in Convection:

A

With Air flow (can be sensible or latent)

40
Q

Heat transfer happens in Radiation:

A

With no contact

41
Q

Heating loads critical design conditions:

A

Coldest weather
Night time
Low activity
Outside Temp.

42
Q

Cooling loads critical design conditions:

A

Peak temp. and humidity
Daytime
High activity
Outside temp.

43
Q

Heat transfer equation using area, temperature, and resistance:

A

Q = A x TD / R (Btu / h)

44
Q

Insulation requires __________ conductivity

A

Low

45
Q

Conductors require __________ conductivity

A

High

46
Q

R value

A

Resistance to heat transfer

47
Q

Heating load is expressed as:

A

Qsensible

48
Q

Humidification load is expressed as:

A

Qlatent

49
Q

When calculating heating loads (heat lost, wintertime), use (TD or TETD):

A

TD

50
Q

When calculating cooling loads (heat gained, summertime), use (TD or TETD):

A

TETD

51
Q

When calculating heating loads (heat lost, wintertime), should you include latent loads?

A

No

52
Q

When calculating cooling loads (heat gained, summertime), should you include latent loads?

A

Yes

53
Q

Heat constant for people:

A

250 Btu / h

building environmental systems (2 decks)

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