[L2]_A/C, Thermodynamics, & Psychrometrics - Part I & II

Question 1

IND405

What is the dB, RH%, W, & dew-point at the shown location?

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Answer 1

• dB = 72-degrees (F)
• RH% = 44%
• W = 50 grains/lb
• Dew-Point = 48-degrees (F)

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Question 2

IND405

True or False: A typical Heat Pump cycle is the refrigeration cycle in reverse.

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Answer 2

True.

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Question 3

IND405

What activities will occur at 100%RH?

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Answer 3

1. Condensation of an object
2. Fog in an open outdoor area

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Question 4

IND405

What type of air is defined by the U.S. Standard Atmosphere and why?

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Answer 4

Dry air becuase is behaves as a perfect gas.

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Question 5

IND405

What type of HVAC equipment is recommended for OA CFM loads greater than 20% of the total SA CFM?

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Answer 5

DOAS Units = Dedicatied Outside Air Systems

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Question 6

IND405

What chart is used for the analysis of the state for Steam?

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Answer 6

Mollier Diagram of Entropy vs Enthalpy

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Question 7

IND405

What design code standard is ASHRAE 62.1?

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Answer 7

Ventilation and Acceptable Indoor Air Qualit

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Question 8

IND405

What design code standard is ASHRAE 90.1?

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Answer 8

Energy Standard for Buildings Except Low-Rise Residential Buildings

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Question 9

IND405

Define Psychrometrics.

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Answer 9

The field of science concerned with the determination of physical and thermodynamic properties of gas vapor mixtures.

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Question 10

IND405

True or False: Heat energy can flow from a lower temperature substance to a higher temperature substance.

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Answer 10

False.

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Question 11

IND405

What is the formula in finding the Quality of a mixture via its Enthalpy?

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Answer 11

hx = ((1-x)hL) + (xhV)

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Question 12

IND405

Which is always the coldest temperature out of the (3) provided?
* Dry-Bulb
* Dew Point
* Wet-Bulb

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Answer 12

Dew-Point Temperature

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Question 13

IND405

What is the formula in finding the Quality of a mixture via its Specific Volume?

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Answer 13

νx = ((1-x)νL) + (xνv)

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Question 14

IND405

What is the definition of Entropy and it’s most base formula?

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Answer 14

• The measure of molecular disorder/breakdown in a given state; as the breakdown is furthered the entropy (S) is increased.
• S = k*lnW

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Question 15

IND405

What design code standard is NFPA 92?

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Answer 15

Standard for Smoke Control System

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Question 16

IND405

What is the typical HVAC equipment $/Ton of cooling?

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Answer 16

$2,000/Ton

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Question 17

IND405

How many Btu/hr are in 1-Ton of cooling?

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Answer 17

12,000 Btu/h

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Question 18

IND405

What year was the first electric air-conditioning system invented and by whom?

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Answer 18

Willis Haviland Carrier in 1902

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Question 19

IND405

What was the first year the ASHRAE organization was formed in the U.S.?

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Answer 19

1904

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Question 20

IND405

Name the five (5) HVAC design system calculations required

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Answer 20

1. Maximum heating & cooling loads for the spaces to be served
2. The type of HVAC system to be selected and utilized in the served space
3. Calculation and sizing of piping and/or ductwork
4. Equipment component selection and sizing (heat exchangers, boilers, chillers, fans, etc.)
5. Design layout of the system focusing on costs, IAQ, & energy conservation in mind

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Question 21

IND405

What are the two (2) primary functions of an HVAC System?

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Answer 21

1. To generate and maintain the comfort level for occupants in a conditioned space
2. The supplying of a set of environmental conditions for a process or product within a space

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Question 22

IND405

List the three (3) typical formulas for calculating the SHR?

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Answer 22

1. SHR = Qsensible/Qtotal
2. SHR = Qsensible/(Qsensible + Qlatent)
3. SHR = cp*(t2-t1)/(h2-h1)

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Question 23

IND405

Define Thermodynamics.

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Answer 23

The science devoted to the study of energy, its transformations, and its relation to status of matter.

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Question 24

IND405

What is the constant R value for typical air in imperial units?

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Answer 24

R = 53.352 (ft-lbf)/(lbm-R)

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Question 25

# IND405 What is the name of the code standard focusing on the **Thermal Comfort of Humans**? ## Footnote [L2]

Answer 25

ASHRAE 55 ## Footnote [L2]

Question 26

# IND405 List the **seven (7)** important parameters from a Psycrometric chart. ## Footnote [L2]

Answer 26

1. Dry-Bulb 2. Wet-Bulb 3. Relative Humidity 4. Dew Point 5. Humidity Ratio 6. Specific Volume 7. Enthalpy ## Footnote [L2]

Question 27

# IND405 What is the definition of **Quality** in regards to steam? ## Footnote [L2]

Answer 27

It is the ratio of the mass of vapor to total mass of liquid plus vapor when a substance is in a saturation state. ## Footnote [L2]

Question 28

# IND405 List the **four (4)** states of the **Refrigeration Cycle**. ## Footnote [L2]

Answer 28

1. Expansion 2. Evaporator 3. Compression 4. Condensing ## Footnote [L2]

Question 29

# IND405 * How many **state change processes** can occur on a Psychrometric Chart? * Name **each** of them. ## Footnote [L2]

Answer 29

* There are **eight (8)** state change processes. 1. Humidication 2. Heating + Humidification 3. Sensible Heating 4. Heating + Dehumidification 5. Dehumidification 6. Cooling + Dehumidification 7. Sensible Cooling 8. Cooling + Humidification ## Footnote [L2]

Question 30

# IND405 What is the **1st professional license test** you can sit for after graduating from your Bachelor's degree? ## Footnote [L2]

Answer 30

The Fundamentals of Engineering Exam (FE) or The Engineering In Training Exam (EIT) ## Footnote [L2]

Question 31

# IND405 Define what a **BTU** is. ## Footnote [L2]

Answer 31

Is the amount of heat energy needed to raise the temperature of one (1lb) of water by one (1) degree F. ## Footnote [L2]

Question 32

# IND405 Define **Latent Heat**. ## Footnote [L2]

Answer 32

Heat energy change associated with the addition or removal of moisture from a substance. ## Footnote [L2]

Question 33

# IND405 Define **Sensible Heat**. ## Footnote [L2]

Answer 33

Heat energy that, when added to or removed from a substance, results in a measurable change in dry bulb temperature. ## Footnote [L2]

Question 34

# IND405 **True or False:** A theoretical cooling process is carted exactly the same on a psychrometric chart as an in field cooling process. ## Footnote [L2]

Answer 34

False. ## Footnote [L2]

Question 35

# IND405 Should Professionally Licensed Engineers design using **Rule of Thumb** guidelines only? ## Footnote [L2]

Answer 35

No. ## Footnote [L2]

Question 36

# IND405 If a space needs to provide **OA** during the **summer**, what **process** must occur to create a **MA** stream? ## Footnote [L2]

Answer 36

Cooling + Dehumidification ## Footnote [L2]

Question 37

# IND405 What is the formula for ideal gases in terms of **pv** & also **enthalpy**? ## Footnote [L2]

Answer 37

* pv = mRT * h = u + pv = u+RT ## Footnote [L2]

Question 38

# IND405 What is the definition of **Enthalpy** and it's most base formula? ## Footnote [L2]

Answer 38

* The change of state for a substance defined as (h) * H = U + pV ## Footnote [L2]

Question 39

# IND405 List the **(3) Laws of Thermodynamics** and what they are. ## Footnote [L2]

Answer 39

1. **First Law**: Energy cannot be created nor destroyed 2. **Second Law**: The total entropy of the universe must increae in every spontaneous process 3. **Third Law**: The Entropy (S) of a pure, perfectly crystalline compound at T=0 degree (K) or absolute 0 is **ZERO** ## Footnote [L2]

Question 40

# IND405 What is the formula in finding the **Quality** of a **mixture** via its **Entropy**? ## Footnote [L2]

Answer 40

sx = ((1-x)*sL) + (x*sv) ## Footnote [L2]

Question 41

# IND405 What is the formula in finding the **Quality** of a **mixture** via its **Internal Energy**? ## Footnote [L2]

Answer 41

ux = ((1-x)*uL) + (x*uv) ## Footnote [L2]

Question 42

# IND405 What year was the **first electric refrigerator invented** and by whom? ## Footnote [L2]

Answer 42

Fred W. Wolf in 1913 ## Footnote [L2]

Question 43

# IND405 What is the parameter highlighted in **RED** from the image and define it. ## Footnote [L2]

Answer 43

Wet Bulb (wb) is when the evaporation rate reaches equilibrium with moisture content of the surrounding air. ## Footnote [L2]

Question 44

# IND405 What is the **formula** needed for calculating latent heat in terms of **pounds of water**? ## Footnote [L2]

Answer 44

Ql = 4840 * CFM * ∆W ## Footnote [L2]

Question 45

# IND405 What is the parameter highlighted in **RED** from the image and define it. ## Footnote [L2]

Answer 45

Dry Bulb Temperature (db) is the temperature of air measured by a thermometer exposed to the air but is shielded from radiation and moisture. ## Footnote [L2]

Question 46

# IND405 What design code standard is **Article 690**? ## Footnote [L2]

Answer 46

National Electric Code ## Footnote [L2]

Question 47

# IND405 What is the parameter highlighted in **RED** from the image and define it. ## Footnote [L2]

Answer 47

Relative Humidity (RH%) is the percent of saturation at a given dry bulb temperature. ## Footnote [L2]

Question 48

# IND405 What is the **name** of this equipment? ## Footnote [L2]

Answer 48

DOAS (Dedicated Outdoor Air System) ## Footnote [L2]

Question 49

# IND405 What is the typical equation for the **Quality** of **Steam**? ## Footnote [L2]

Answer 49

x = mvapor/(mvapor + mliquid) ## Footnote [L2]

Question 50

# IND405 List the three **(3)** types of **Heat Transfer** possible. ## Footnote [L2]

Answer 50

1. Conduction 2. Convection 3. Radiation ## Footnote [L2]