BS: Lesson 3 - Basic Thermal Process

Question 1

What is temperature?

Answer 1

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

Question 2

What is heat?

Answer 2

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.

Question 3

What is sensible heat?

Answer 3

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

Question 4

What is latent heat?

Answer 4

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

Question 5

How is heat transferred?

Answer 5

radiation

convection

conduction

latent heat (evaporation)

Question 6

The rate of radiation exchange is based on what?

Answer 6

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

Question 7

Emissivity is

Answer 7

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

Question 8

True or False:

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

Answer 8

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

Question 9

True or False.

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

Answer 9

True.

Question 10

Selective surfaces

Answer 10

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

Question 11

Which gases contribute to the earth’s greenhouse effect?

Answer 11

Carbon dioxide

Methane

Nitrous oxide

Chlorofluorocarbons

Question 12

Mean radiant temperature

Answer 12

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

Question 13

A globe thermometer is used to measure what?

Answer 13

Mean radiant temperature

Question 14

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

Answer 14

Our metabolism, clothing and environment.

Question 15

True or False.

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

Answer 15

True.

Question 16

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

Answer 16

Evaporation with dry moving air.

Question 17

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

Answer 17

Evaporation decreases.

Question 18

Conduction

Answer 18

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

Question 19

True or False.

Conduction is not directional

Answer 19

True.

Question 20

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

Answer 20

Resistivity is the inverse of conductivity

Question 21

True or False.

In buildings, conduction does not occur inside walls.

Answer 21

False.

Question 22

How thick in R19 batt insulation?

Answer 22

6 1/2”

Question 23

How thick is R15 batt insulation?

Answer 23

3 1/2”

Question 24

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

Answer 24

Compressing its thickness.

Question 25

Power.

Answer 25

The rate of energy usage over time.

Question 26

R19 insulation is how thick?

Answer 26

6-1/4"

Question 27

1 Horsepower = approx. ____ Btu/h

Answer 27

2,545 Btu/h

Question 28

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

Answer 28

sum of all of the losses

Question 29

Heating Load Calculation: Heat flow is a product of _______ and is expressed in the equation ____________.

Answer 29

the conductance of the assembly heat flow = (U value) x (area) x (temp difference)

Question 30

Heating degree day

Answer 30

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.

Question 31

Design day

Answer 31

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

Question 32

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

Answer 32

people lighting equipment

Question 33

How many Btuh does a human being generate at rest?

Answer 33

450 Btuh

Question 34

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

Answer 34

2,500 Btuh

Question 35

What is brake horsepower (Bhp)

Answer 35

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.

Question 36

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

Answer 36

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

Question 37

Insolation

Answer 37

The radiant gain through glass.

Question 38

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

Answer 38

heat flow

Question 39

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

Answer 39

slab on grade heat loss

Question 40

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

Answer 40

infiltration load

Question 41

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

Answer 41

cooling load for people

Question 42

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

Answer 42

cooling load for lighting

Question 43

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

Answer 43

cooling load for mechanical or equipment

Question 44

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

Answer 44

heat gain through walls/roofs

Question 45

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

Answer 45

radiant heat gain through windows

Question 46

Heating loads are calculation using the formula: q_tot = q_ x + q_ x + q_ x

Answer 46

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

Question 47

Cooling loads are calculation using the formula: q_tot = q_ x + q_ x + q_ x + q_ x

Answer 47

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

Question 47

Specific heat

Answer 47

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

Question 48

Active solar systems are used to do one of four things

Answer 48

heat water heat the building cool the building or generate electricity

Question 49

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

Answer 49

heating water

Question 50

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

Answer 50

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.

Question 51

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

Answer 51

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".

Question 52

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

Answer 52

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)

Question 53

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

Answer 53

air and rock bed storage hydronics

Question 54

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

Answer 54

the desicant system the absorption refrigeration cycle

Question 55

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

Answer 55

the DC to AC conversion process

Question 56

What is the most efficient passive solar heating system?

Answer 56

Photovoltaics

Question 57

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

Answer 57

10 mph

Question 58

What are the two types of wind turbines?

Answer 58

vertical axis horizontal axis

Question 59

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

Answer 59

``` 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 ```

Question 60

What is the most common type of wind turbine?

Answer 60

horizontal axis

Question 61

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

Answer 61

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

Question 62

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

Answer 62

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