[L7]_Cooling Loads - Part I Flashcards
IND405
What is the difference between space and system loads?
[L7]
Space load calculated include the necessary values to satify the envelope load, but does not account for other heat gains/losses that occur from equipment outside of the envelope.
[L7]
IND405
(Yes or No) It is possible to have a scenario where HVAC equipment heat gain loads can be larger than the combined space loads of a project?
[L7]
Yes.
[L7]
IND405
List the four (4) common System Loads outside of Space Loads.
[L7]
- Infiltration/Ventilation Load
- AHU Fan Load
- Ductwork Load
- Plenum Load
[L7]
IND405
What is the most common type of ventilation for existing building projects?
* Natural Ventilation
* Mechanical Ventilation
[L7]
Natural Ventilation
[L7]
IND405
What is the difference between Block & Peak building loads?
[L7]
Peak loads mean that the size of the system is based on the total peak CFMs in each room, while block loads mean that the size of the system is based on when the building as a whole is busy.
[L7]
IND405
To obtain the maximum amount of comfort in a space which is better? Single-Zone T-Stat or Multi-Zone T-Stat
[L7]
Multi-Zone T-Stat
[L7]
IND405
What is the largest heat gain or loss in terms of system loads?
a) Miscellaneous heat gain
b) Ductwork heat gain
c) Outdoor air introduced in mechanical ventilation
[L7]
Outdoor air introduced in mechanical ventilation
[L7]
IND405
What is the purpose of a psychrometric chart?
[L7]
To determine the properties of air, such as temperature, humidity, and enthalpy in order to calculate HVAC system loads at specific outdoor and indoor design temperatures.
[L7]
IND405
What is an economizer cycle?
[L7]
A cycle that uses outdoor air to cool a space instead of mechanical refrigeration.
[L7]
IND405
What is an Air-Barrier?
[L7]
A material or system that prevents the movement of air through the building envelope.
[L7]
IND405
What is an Insulation Barrier?
[L7]
A material or system that reduces heat transfer through the building envelope.
[L7]
IND405
What is thermal bridging?
[L7]
The transfer of heat through materials that are poor insulators, such as metal studs or concrete slabs.
[L7]
IND405
In a window, do you usually want or not a thermal break?
[L7]
Yes, you want to include a thermal break to stop heat transfer through the window frame.
[L7]
IND405
Latent heat gain in a building is caused by which of the following?
A. Solar radiation
B. Ventilation and occupants
C. High thermal mass walls
D. Dark roofs
[L7]
B. Ventilation and Occupants
[L7]
IND405
Match the equation component with its description:
1. U
2. A
3. CLTDCorrected
A. Cooling Load Temperature Difference (adjusted for conditions)
B. Area of the surface being analyzed
C. Overall heat transfer coefficient
[L7]
1 = C
2 = B
3 = A
[L7]
IND405
True/False: The sun is directly overhead at 23.5°S latitude on June 21st.
[L7]
False
[L7]
IND405
What is the typical summer indoor design condition for most comfort systems?
A. 65°F and 60% RH
B. 75°F and 50% RH
C. 70°F and 40% RH
D. 80°F and 55% RH
[L7]
B. 75°F and 50% RH
[L7]
IND405
Calculate the Cooling Degree Days (CDD65) for a day with an average outdoor temperature of 90°F.
[L7]
CDD65 = 90°F - 65°F = 25°F
[L7]
IND405
The equation 𝑄𝑆 = 𝑈⋅𝐴⋅𝐶𝐿𝑇𝐷 𝐶𝑜𝑟𝑟𝑒𝑐𝑡𝑒𝑑 is used to calculate ________.
[L7]
Sensible Heat Gain
[L7]
IND405
True/False: A roof with a U-value of 0.055, an area of 5,478 ft², and a corrected CLTD of 61.5 has a peak hour BTU load of 18,529.33 BTU/hr.
[L7]
True
[L7]
IND405
Which factor influences solar heat gain through windows the most?
A. Thermal mass of the window frame
B. Solar Heat Gain Coefficient (SHGC)
C. Type of window shading
D. CLTD of the exterior wall
[L7]
B. Solar Heat Gain Coefficient (SHGC)
[L7]
IND405
True/False: Solar transmission through glass includes both conductive and radiative components.
[L7]
True
[L7]
IND405
The cooling load for glass radiation transmission is calculated using the equation 𝑄𝐺𝑙𝑎𝑠𝑠𝑆𝑜𝑙𝑎𝑟 = 𝐴⋅𝑆𝐻𝐺𝐹⋅𝐶𝐿𝐹
[L7]
True
[L7]
IND405
Match the ventilation scenario to the space type:
1. Public Restrooms
2. Clean Rooms
3. Operating Rooms
A. Scenario 1 (100% outdoor air)
B. Scenario 2 (exhaust-only)
C. Scenario 3 (high ACH)
[L7]
1 = B
2 = A
3 = A
[L7]
IND405
Calculate the total heat gain 𝑞𝑇 using 𝑄=2,000 CFM, and Δℎ = 25 Btu/lbm.
[L7]
qT = 4.5⋅Q⋅Δh
𝑞𝑇 = 4.5⋅2,000⋅25 = 225,000-Btu/hr
[L7]
