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.

Residential building cooling load

Figure 8-2 Actual cooling load and solar heat gain for light, medium, and heavy construction.

Residential building cooling load

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

CLTD/GLF Method

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


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