Residential building cooling load
Heat gain: The rate at which energy is transferred to or generated within a space Cooling load: The rate at which energy must be removed from a space to maintain the temperature and humidity at the design values
Heat gain ^ Cooling load (radiation, thermal mass, thermal lag)
Heat extraction: The rate at which energy is removed from the space by the cooling and dehumidification equipment.
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Figure 8-2 Actual cooling load and solar heat gain for light, medium, and heavy construction. |
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Figure 8-1 Schematic relation of heat gain to cooling load. |
Cooling loads:
• through structural components
• through windows
• by infiltration
• due to occupants and appliances
The method uses regression data of computer generated transfer function solution.
Calculation procedure:
• Cooling load through structural components:
Cooling Load Temperature Difference (CLTD) combines the temperature difference between indoor and outdoor and solar radiation and considers thermal capacity of the enclosure.
Q = U A (CLTD)
U = overall heat transfer coefficient A = area of roof, wall, or glass
CLTD = cooling load temperature difference; tabulated for flat roofs, walls, glasses (Table A27-1 and A27-22)
• Cooling load through windows:
Glass Load Factor (GLF) includes effects of both transmission and solar radiation Q = (GLF) A
GLF = glass load factor (Table A27-3 and A27-4)
• Cooling load due to infiltration:
Q = (ACH) Vroom (T0 — TO x 1200/3600
• Cooling load due to occupants and appliances:
People:
Q = 70 W/person Appliances:
Q = 470 W for both kitchen and laundry for single family Q = 350 W for multi-family
For latent cooling load:
• Calculate from individual components or estimate as 30% of the sensible load
Posted in Fundamentals of Heating. Ventilating, and Air-Conditioning