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A.R.E. - Building Systems > BS: Lesson 3 - Basic Thermal Process > Flashcards

BS: Lesson 3 - Basic Thermal Process Flashcards

1
Q

What is temperature?

A

Temperature is a measure of stored heat energy. Temperature can never be transferred.

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2
Q

What is heat?

A

Heat is the amount of energy in a system or substance. Heat can be transferred to a substance with or without changing the substances temperature.

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3
Q

What is sensible heat?

A

Heat that changes the temperature of a substance, and does not represent the addition of any moisture to the substance.

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4
Q

What is latent heat?

A

The heat added to or removed from a substance causing it to change its state.

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5
Q

How is heat transferred?

A

radiation

convection

conduction

latent heat (evaporation)

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6
Q

The rate of radiation exchange is based on what?

A
  1. surface temperature of the objects
  2. the viewed angle
  3. emissivity
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7
Q

Emissivity is

A

the rate at which an object gives off heat; its a property of the material

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8
Q

True or False:

A black, dark and/or matte surfaces have higher emissivity and absorptivity than white, light and/or shiny surfaces.

A

True. Black, dark and matte surfaces heat up quickly, but cool rapidly.

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9
Q

True or False.

White, light and shiny surfaces heat up slower than black, dark and matte surfaces and stay hot longer.

A

True.

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10
Q

Selective surfaces

A

Surfaces that have a high absorptivity in one wavelength (usually solar) and low emissivity in another wavelength (usually infrared).

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11
Q

Which gases contribute to the earth’s greenhouse effect?

A

Carbon dioxide

Methane

Nitrous oxide

Chlorofluorocarbons

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12
Q

Mean radiant temperature

A

The average radiant temperature of your surroundings. It is independent of air temperature.

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13
Q

A globe thermometer is used to measure what?

A

Mean radiant temperature

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14
Q

The amount of heat one looses from conduction, convection, radiation and/or evaporation is based the interaction between what?

A

Our metabolism, clothing and environment.

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15
Q

True or False.

A liquid can evaporate only by removing large quantities of heat from the surface it is leaving.

A

True.

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16
Q

As air and surface temperatures approach our own body temperatures, what form of heat flow is most beneficial to help cool the body?

A

Evaporation with dry moving air.

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17
Q

As air and surface temperatures decrease, evaporation increases or decreases.

A

Evaporation decreases.

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18
Q

Conduction

A

The heat follow process that occurs when objects are in direct contact. It is not directional.

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19
Q

True or False.

Conduction is not directional

A

True.

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20
Q

How is resistivity (r) and conductivity (k) related?

A

Resistivity is the inverse of conductivity

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21
Q

True or False.

In buildings, conduction does not occur inside walls.

A

False.

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22
Q

How thick in R19 batt insulation?

A

6 1/2”

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23
Q

How thick is R15 batt insulation?

A

3 1/2”

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24
Q

What is one way to reduce the value of batt insulation?

A

Compressing its thickness.

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25
Q

Power.

A

The rate of energy usage over time.

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26
Q

R19 insulation is how thick?

27
Q

1 Horsepower = approx. ____ Btu/h

A

2,545 Btu/h

28
Q

The heating load of a building consists of the _______ thru the building skin.

A

sum of all of the losses

29
Q

Heating Load Calculation:

Heat flow is a product of _______ and is expressed in the equation ____________.

A

the conductance of the assembly

heat flow = (U value) x (area) x (temp difference)

30
Q

Heating degree day

A

A measure of how cold it is in one place over a period of time. It is the number of days the temperature is below the base temperature of 65º.

31
Q

Design day

A

A day colder than 98% of the days experienced in that climate.

32
Q

What are the 3 internal heat sources used to size cooling equipment?

A

people

lighting

equipment

33
Q

How many Btuh does a human being generate at rest?

34
Q

How many Btuh does a human being generate when engaged in heavy work or athletic activity?

A

2,500 Btuh

35
Q

What is brake horsepower (Bhp)

A

The measurement of an engines horsepower before factoring in loss of horsepower due to its components (pulleys, pumps, gears, etc). A measure of true horsepower.

36
Q

The Cooling Load Temperature Differential (CLTD) is used for what.

A

To size a/c equipment for heat gain/loss and cooling.

37
Q

Insolation

A

The radiant gain through glass.

38
Q

In regards to Heating Load calculations, what is q_c (q sub c)

39
Q

In regards to Heating Load calculations, what is q_s (q sub s)

A

slab on grade heat loss

40
Q

In regards to Heating Load calculations, what is q_i (q sub i)

A

infiltration load

41
Q

In regards to Heating Load calculations, what is q_p (q sub p)

A

cooling load for people

42
Q

In regards to Heating Load calculations, what is q_l (q sub l)

A

cooling load for lighting

43
Q

In regards to Heating Load calculations, what is q_m (q sub m)

A

cooling load for mechanical or equipment

44
Q

In regards to Heating Load calculations, what is q_cltd (q sub cltd)

A

heat gain through walls/roofs

45
Q

In regards to Heating Load calculations, what is q_r (q sub r)

A

radiant heat gain through windows

46
Q

Heating loads are calculation using the formula:

q_tot = q_ x + q_ x + q_ x

A

q_tot = c (heat flow) + s (slab on grade heat loss) + i (air infiltration)

47
Q

Cooling loads are calculation using the formula:

q_tot = q_ x + q_ x + q_ x + q_ x

A

q_tot = p (people) + m (equipment) + i (air infiltration) + r (radiation through windows)

47
Q

Specific heat

A

The amount of heat required to change to temperature of an object by a given amount.

48
Q

Active solar systems are used to do one of four things

A

heat water

heat the building

cool the building

or generate electricity

49
Q

At this time, what is the most effective use of an active solar heating system?

A

heating water

50
Q

What does a drain down system refer to in a active solar heating water heater system?

A

A type of closed-loop system to prevent freezing pipes. The system senses the temperature differential and opens valves to drain the fluid down into the reservoir.

51
Q

What does a drain back system refer to in a active solar heating water heater system?

A

A type of closed-loop system to prevent freezing pipes. A fail safe system in which the collector is only full while the pump is running. If the pump shuts off, everything in the collector “drains back”.

52
Q

Name four types of water heater systems used for an active solar heating system.

A

open-loop (direct system)

closed-loop (indirect system)

batch system (closed-loop system - storage tank exposed to the sun)

thermosiphon system (closed-loop system - storage tank higher than collector; uses convection)

53
Q

What are the two methods of passive solar heating for buildings?

A

air and rock bed storage

hydronics

54
Q

What two methods of passive solar heating are used for cooling?

A

the desicant system

the absorption refrigeration cycle

55
Q

In using photovoltaics for passive solar heating, what is a synchronous inverter?

A

the DC to AC conversion process

56
Q

What is the most efficient passive solar heating system?

A

Photovoltaics

57
Q

What is the average wind speed need for a wind turbine?

58
Q

What are the two types of wind turbines?

A

vertical axis

horizontal axis

59
Q

Name to the two types of vertical axis wind turbines and their advantages and disadvantages.

A 
Savonius (think of a swan, i.e: shape) - composed of two offset cups; or two halves of a steel drum
	Advantages:
		self starting
		works regardless of wind direction
	Disadvantages:
		not very efficient
Darrius (dairy, i.e: shape) - resembles a single egg beater stuck in the ground
	Advantages:
		very efficient
		works regardless of wind direction
	Disadvantages:
		does not self start
60
Q

What is the most common type of wind turbine?

A

horizontal axis

61
Q

When a horizontal axis wind turbine blades are upwind of the tower it is called a_________?

A

a leading configuration (wind hits the blades first, then the fins of the “cowling”)

62
Q

When a horizontal axis wind turbine blades are downwind of the tower it is called a_________?

A

a trailing configuration (the wind hits the “cowling” first, then blades)

A.R.E. - Building Systems (8 decks)

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