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PDD > SYSTEMS - MECHANICAL PDD > Flashcards

SYSTEMS - MECHANICAL PDD Flashcards

1
Q

Emissivity

A

Emissivity - of an object is a measure of its ability to absorb and then radiate heat. Shiny objects have low emissivity

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2
Q

Emittance

A

Emittance - of an object is ratio of the radiation emitted by object or material to that emitted by a black body at the same temperature. Shiny objects have low emissivity

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3
Q

Mean Radiation temperature MRT

A

weighted average of the various surface temperatures in a room and the angle of exposure of occupant to the surfaces, as well as any sunlight present. all room surfaces and the temperatures and positions must be taken into account.

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4
Q

Thermal conductivity K

A

Thermal conductivity K

Rate At Which Heat Passes Through 1 SF Of 1 Inch Thickness Of Material When Temperature Differential Is 1°F

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5
Q

Conductance C

A

Rate At Which Heat Passes Through 1 sf Of Thickness Of Material Other Than One Inch When Temperature Differential Is 1°F

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6
Q

R-value Formula

A

Measure of resistance to heat flow through a given thickness of material. So the higher the R-value, the more thermal resistance the material has and therefore the better its insulating properties

R = 1 / C

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7
Q

Overall coefficient of heat transmission U Formula

A

U = 1 / sum R

CONDUCTANCE OF THE WHOLE ASSEMBLY

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8
Q

Heat Infiltration Formula

A

transfer of air into building through open doors, cracks, around windows, flues, vents etc

Air Infiltration Heat Loss = Room Volume * ΔT * Air Changes / hr * 0.O18

ΔT=Design Temperature Difference

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9
Q

Design cooling load factor DCLF - formula

A

Area Of Glazing * DCLF = Heat Gain through Glazing

DCLF - Design cooling load factor

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10
Q

Heat gain through lighting

A

1 W equals 3.41 Btu/ hr

(for fluorescent lighting W of ballast must be included)

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11
Q

BTU

A

heat required to raise the temperature of 1 LBM water by 1°F

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12
Q

Enthalpy

A

total heat of substance, including latent heat and sensible heat

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13
Q

Specific heat

A

Number of BTUs required to raise the temperature of specific material by 1°F

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14
Q

Balance point temperature:

A

temp at which the building does not require mechanical heating or cooling

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15
Q

sensible heat

A

the temperature of the air

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16
Q

latent heat

A

the moisture content of the air

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17
Q

Temperature at a point in a wall - Formula

A

Toutside + [(Rvalue outside of point in wall/Rvalue total) x ΔT]

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18
Q

The average R-value of sloped insulation

A

The average R-value of sloped insulation is the average of the thickest and thinnest values.

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19
Q

Fibrous filters for dust - maintenance

A

Fibrous filters for dust, must be replaced

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20
Q

electrostatic filters for dust - maintenance

A

electrostatic filters for dust, must be wiped down

21
Q

activated charcoal filters

A

activated charcoal filters for odors or chemicals

22
Q

prallel / opposed blade dampers best for

A

parallel best for on off,

opposed blade dampers based for throttling airflow

23
Q

ASHRAE standards: 90.1

A

energy and lighting

24
Q

ASHRAE standards: 62.1

A

ventilation

25
Q

ASHRAE standards: 55

A

thermal comfort

26
Q

1 horsepower?

1 ton of cooling ?

A

1 horsepower = 2544 BTU/hr,

1 ton of cooling = 12,000 BTU/hr

27
Q

Solar Heat Gain Coefficient (SHGC)

A

ratio of solar heat gain through a fenestration to the total solar radiation incident (falling upon/striking) on the glazing (0.0 - 0.87)

28
Q

Shading Coefficient (SC)

A

ratio of solar heat gain through a glazing product to the solar heat gain through an unshaded 1/8” thick clear double strength glass under the same set of conditions (0.0 - 1.0)

SHGC is considered more accurate.

29
Q

• Poor Indoor Air Quality gets upgraded to Sick Building Syndrome when:

A

10% of occupants are sick

20% of occupants complain

30
Q

calculate daylighting:

A
  • Measure from bottom of floor to the top of the window (doesn’t matter how big it is)
  • You can go 2.5x that length into the building for lighting penetration
  • Daylighting Factor

max = 0.2 (window area/floor area)

min = 0.1 (window area/floor area)

• Remember…it should be between 1% - 5%!

31
Q

• High Efficiency Particulate Arrestance (HEPA) filter

A

• High Efficiency Particulate Arrestance (HEPA) filter:

the highest efficiency option, typically found in special air cleanser for unusually polluted or IAQ demanding environments like hospitals

32
Q

Electric heating

A
  • Radiant heat is run through panels or wires to rooms
  • Low initial cost , Simple system , Can turn on only in occupied room
  • Expensive life cycle cost , Wasteful
  • Baseboard heat uses convection to heat spaces
33
Q

What is an RTU

A

A packaged AHU for larger buildings is also termed a Rooftop Unit (RTU).

An RTU is used as a primary system in buildings because it has enough power to regulate the heating and cooling for a building by itself, or with the assistance of an additional rooftop unit.

34
Q

issues due to having a well-constructed air-tight building

A

The gas fireplace is not working well,

the doors and windows can be difficult to open,

and odors tend to linger.

The goal is to keep the air tight construction while bringing in fresh air.

35
Q

Q. Which of the following best describes why it is important for ductwork to follow a simple, direct path?

Ducts are expensive to install.

Ductwork takes up a significant amount of space.

Round ducts maintain better air pressure.

Ducts can pose acoustical challenges.

A

The correct answer is B.

The correct answer is that ductwork takes up a significant amount of space, and a simple, direct path will help to reduce the amount of space necessary. They are not expensive to install, and pose no acoustical challenges. Although round ducts do maintain better air pressure, that is not a reason to ensure they follow a simple, direct path.

36
Q

R value formula

A
37
Q

Outdoor air, infiltarion formula

A

qinfiltration = (Aexposed) (infiltration factor)

Aexposed- Area of exposed wall surface, including fenestration.

Infiltration Factor- Should be presented in a tabulated format.

Outdoor air includes mechanically introduced outdoor air.

38
Q

Cooling Degree Day - CDD

A

A cooling degree day (CDD) is a measurement designed to quantify the demand for energy needed to cool
a building

CDD is the number of degrees that a day’s average temperature is above 65° Fahrenheit.

39
Q

Important Formula for Heating Capacity (Btu/h)

A
40
Q

Calculating Btu Cooling

A
41
Q

1 ton cooling capacity

A

1 ton cooling capacity
= 12,000Btu/h or 3,516 W

42
Q

Effective Temperature:

A

Effective Temperature: fictitious temperature that produces the same physiological

effect as the combined effects of temperature, humidity, and air movement NOT AN

ACUTAL TEMPERATURE.

43
Q

measuring instruments temp

A

Barometer: an instrument for measuring atmospheric pressure

Globe Thermometer: used to measure radiant temperature. It’s a dry bulb thermometer, encased in a matte black copper sphere

Hygrometer: instrument used to measure the relative humidity of the air

44
Q

CFM formula

A

cfm=(space volume) x ACH / (60 min/hr)

Start with the total volume of air (in cubic feet), divide by the exchange rate (ach/ how quickly you want to replace the air), and the result is the total CFM (cubic feet per minute) you need for your system

45
Q

Heat Gain (q, in BTU/hr)!

A

Heat Gain (q, in BTU/hr) = U value x Area, A x (∆T)

46
Q

Balance Point (Tbalance )

A

The building balance point temperature is the outdoor air temperature when the heat gains of the building are equal to the heat losses.

Internal heat sources due to electric lighting, mechanical equipment, body heat, and solar radiation may offset the need for additional heating although the outdoor temperature may be below the thermostat set-point temperature. The building balance point temperature is the base temperature necessary to calculate heating degree day to anticipate the annual energy demand to heat a building. The balance point temperature is a consequence of building design and function rather than outdoor weather conditions

47
Q

• A typical US home uses about ? BTU/year (amount) for space heating

A

• A typical US home uses about 50 MILLION BTU/year (amount) for space heating

48
Q

Heating Degree Days (HDD65)

A

0-1000 no problem, no need to heat

1000 - 3000 good insulation is enough

3000 - 5000 moderate, use 2 systems

5000 - 7000 need serious heating

Over 7000 year long heating (just move)

• Ex: Phoenix HDD65 = 444, Portland = 4693, and Anchorage = 10825

49
Q

CFM temperature rise method

A

CFM = BTUHoutput / (1.08 x DeltaT)

PDD (20 decks)

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