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hvac systems_sp24 > [L2]_A/C, Thermodynamics, & Psychrometrics - Part I & II > Flashcards

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

1
Q

IND405

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

[L2]

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

[L2]

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2
Q

IND405

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

[L2]

A

True.

[L2]

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3
Q

IND405

What activities will occur at 100%RH?

[L2]

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

[L2]

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4
Q

IND405

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

[L2]

A

Dry air becuase is behaves as a perfect gas.

[L2]

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5
Q

IND405

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

[L2]

A

DOAS Units = Dedicatied Outside Air Systems

[L2]

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6
Q

IND405

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

[L2]

A

Mollier Diagram of Entropy vs Enthalpy

[L2]

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7
Q

IND405

What design code standard is ASHRAE 62.1?

[L2]

A

Ventilation and Acceptable Indoor Air Qualit

[L2]

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8
Q

IND405

What design code standard is ASHRAE 90.1?

[L2]

A

Energy Standard for Buildings Except Low-Rise Residential Buildings

[L2]

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9
Q

IND405

Define Psychrometrics.

[L2]

A

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

[L2]

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10
Q

IND405

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

[L2]

A

False.

[L2]

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11
Q

IND405

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

[L2]

A

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

[L2]

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12
Q

IND405

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

[L2]

A

Dew-Point Temperature

[L2]

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13
Q

IND405

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

[L2]

A

νx = ((1-x)νL) + (xνv)

[L2]

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14
Q

IND405

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

[L2]

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

[L2]

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15
Q

IND405

What design code standard is NFPA 92?

[L2]

A

Standard for Smoke Control System

[L2]

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16
Q

IND405

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

[L2]

A

$2,000/Ton

[L2]

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17
Q

IND405

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

[L2]

A

12,000 Btu/h

[L2]

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18
Q

IND405

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

[L2]

A

Willis Haviland Carrier in 1902

[L2]

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19
Q

IND405

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

[L2]

A

1904

[L2]

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20
Q

IND405

Name the five (5) HVAC design system calculations required

[L2]

A
  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

[L2]

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21
Q

IND405

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

[L2]

A
  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

[L2]

22
Q

IND405

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

[L2]

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

[L2]

23
Q

IND405

Define Thermodynamics.

[L2]

A

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

[L2]

24
Q

IND405

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

[L2]

A

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

[L2]

25
Q

IND405

What is the name of the code standard focusing on the Thermal Comfort of Humans?

[L2]

A

ASHRAE 55

[L2]

26
Q

IND405

List the seven (7) important parameters from a Psycrometric chart.

[L2]

A
  1. Dry-Bulb
  2. Wet-Bulb
  3. Relative Humidity
  4. Dew Point
  5. Humidity Ratio
  6. Specific Volume
  7. Enthalpy

[L2]

27
Q

IND405

What is the definition of Quality in regards to steam?

[L2]

A

It is the ratio of the mass of vapor to total mass of liquid plus vapor when a substance is in a saturation state.

[L2]

28
Q

IND405

List the four (4) states of the Refrigeration Cycle.

[L2]

A
  1. Expansion
  2. Evaporator
  3. Compression
  4. Condensing

[L2]

29
Q

IND405

  • How many state change processes can occur on a Psychrometric Chart?
  • Name each of them.

[L2]

A
  • 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

[L2]

30
Q

IND405

What is the 1st professional license test you can sit for after graduating from your Bachelor’s degree?

[L2]

A

The Fundamentals of Engineering Exam (FE) or The Engineering In Training Exam (EIT)

[L2]

31
Q

IND405

Define what a BTU is.

[L2]

A

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

[L2]

32
Q

IND405

Define Latent Heat.

[L2]

A

Heat energy change associated with the addition or removal of moisture from a substance.

[L2]

33
Q

IND405

Define Sensible Heat.

[L2]

A

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

[L2]

34
Q

IND405

True or False: A theoretical cooling process is carted exactly the same on a psychrometric chart as an in field cooling process.

[L2]

A

False.

[L2]

35
Q

IND405

Should Professionally Licensed Engineers design using Rule of Thumb guidelines only?

[L2]

A

No.

[L2]

36
Q

IND405

If a space needs to provide OA during the summer, what process must occur to create a MA stream?

[L2]

A

Cooling + Dehumidification

[L2]

37
Q

IND405

What is the formula for ideal gases in terms of pv & also enthalpy?

[L2]

A
  • pv = mRT
  • h = u + pv = u+RT

[L2]

38
Q

IND405

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

[L2]

A
  • The change of state for a substance defined as (h)
  • H = U + pV

[L2]

39
Q

IND405

List the (3) Laws of Thermodynamics and what they are.

[L2]

A
  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

[L2]

40
Q

IND405

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

[L2]

A

sx = ((1-x)sL) + (xsv)

[L2]

41
Q

IND405

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

[L2]

A

ux = ((1-x)uL) + (xuv)

[L2]

42
Q

IND405

What year was the first electric refrigerator invented and by whom?

[L2]

A

Fred W. Wolf in 1913

[L2]

43
Q

IND405

What is the parameter highlighted in RED from the image and define it.

[L2]

A

Wet Bulb (wb) is when the evaporation rate reaches equilibrium with moisture content of the surrounding air.

[L2]

44
Q

IND405

What is the formula needed for calculating latent heat in terms of pounds of water?

[L2]

A

Ql = 4840 * CFM * ∆W

[L2]

45
Q

IND405

What is the parameter highlighted in RED from the image and define it.

[L2]

A

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

[L2]

46
Q

IND405

What design code standard is Article 690?

[L2]

A

National Electric Code

[L2]

47
Q

IND405

What is the parameter highlighted in RED from the image and define it.

[L2]

A

Relative Humidity (RH%) is the percent of saturation at a given dry bulb temperature.

[L2]

48
Q

IND405

What is the name of this equipment?

[L2]

A

DOAS (Dedicated Outdoor Air System)

[L2]

49
Q

IND405

What is the typical equation for the Quality of Steam?

[L2]

A

x = mvapor/(mvapor + mliquid)

[L2]

50
Q

IND405

List the three (3) types of Heat Transfer possible.

[L2]

A
  1. Conduction
  2. Convection
  3. Radiation

[L2]

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