Handbook of air conditioning and refrigeration / Shan K

6.18 CHAPTER SIX
Space latent heat gain for occupants staying in a conditioned space at time t, denoted by q lp,t, Btu/h
(W), is given as
q lp,t � N p,t(LHG p) (6.15)
where LHG p � latent heat gain of each person, Btu/h (W). Table 6.1 lists the heat gain from occupants
in conditioned space, as abridged from ASHRAE Handbook 1989, Fundamentals. In Table
6.1, total heat is the sum of sensible and latent heat. The adjusted heat is based on a normally
distributed percentage of men, women, and children among the occupants.
Lighting. The sensible heat gains from the electric lights depend on the types of installation, as
follows:
Inside Conditioned Space. For electric lights installed inside the conditioned space, such as
light fixtures hung below the ceiling, the sensible heat gain released from the electric lights, the
emitting element, and light fixtures q s, l is equal to the sensible heat released to the conditioned
space q es, l, Btu/h (W); both depend mainly on the criteria of illumination and the type and efficiency
of electric lights and can be calculated as
q s.l � 3.413 W lamp F uslF al
� 3.413 WAAfl where Wlamp � rated input of electric lights, W
WA � wattage per ft2 of floor area, W/ft 2 (W/m 2 )
Fusl � ratio of wattage in use to installation wattage
(6.16)
In Eq. (6.16), F al indicates an allowance factor for light fixtures, such as Ballast losses. For rapidstart
40-W fluorescent fixtures, F al varies from 1.18 to 1.3 with a recommended value of 1.2
(ASHRAE Handbook 1993, Fundamentals).
Recess-Mounted Fixtures Using Return Plenum. For situations in which electric lights are
recess-mounted on the ceiling and the ceiling plenum is used as a return plenum, the fraction of the
TABLE 6.1 Rates of Heat Gain from Occupants of Conditioned Spaces*
Total heat Total heat Sensible
of adults, adjusted, † heat, Latent heat,
Degree of activity Typical application male, Btu/h Btu/h Btu/h Btu/h
Seated at theater Theater—matinee 390 330 225 105
Seated at theater Theater—evening 390 350 245 105
Seated, very light work Offices, hotels, apartments 450 400 245 155
Moderately active office work Offices, hotels, apartments 475 450 250 200
Standing, light work; walking Department store, retail store 550 450 250 200
Walking; standing Drugstore, bank 550 500 250 250
Light bench work Factory 800 750 275 475
Moderate dancing Dance hall 900 850 305 545
Walking 3 m/h; light machine work Factory 1000 1000 375 625
Heavy work Factory 1500 1450 580 870
Heavy machine work; lifting Factory 1600 1600 635 965
Athletics Gymnasium 2000 1800 710 1090
*Tabulated values are based on 75°F room dry-bulb temperature. For 80°F room dry-bulb temperature, the total heat remains the same, but the
sensible heat values should be decreased by approximately 20 percent and the latent heat values increased accordingly. All values are rounded to
nearest 5 Btu/h.
† Adjusted heat gain is based on normal percentage of men, women, and children for the application listed, with the postulate that the gain from
an adult female is 85 percent of that for an adult male, and that the gain from a child is 75 percent of that for an adult male.
Sources: Adapted with permission from ASHRAE Handbook 1989, Fundamentals.