OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
The total light wattage is obtained from the ratings of all lamps installed, both for general illumination and for
display use.
The use factor is the ratio of the wattage in use, for the condition under which the load estimate is being made,
to the total installed wattage. For commercial applications, such as stores, the use factor is unity
The special allowance factor is for fluorescent fixtures that are either ventilated or installed so that only part of
the heat goes to the conditioned space. For fluorescent fixtures, the special allowance factor primarily accounts
for ballast losses and can be as high as 2.19 for 32W single-lump high-output fixtures on 227V circuits.
Heat Gain from Occupants
Human beings give off heat at a metabolic rate, which depends on their rate of working. The sensible and latent
heat proportion of the heat librated for any given activity depends on the value of the ambient dry bulb
temperature; the lower the dry bulb temperature the larger the proportion of sensible heat dissipated.
Deciding on the density of occupation is usually a problem for the designer. A normal density for an office
block is 9m 2 per person, as an average for the whole conditioned floor area. The density of occupation may be as
high as 20m 2 per person in executive offices or as low as 6m 2 per person in open office areas.
Heat Gain from Equipments
Instantaneous heat gain from equipment operated by electric motors within a conditioned space is calculated as
Where
Qem -heat equivalent of equipment operation, W
P-motor power rating, W
E M -motor efficiency, decimal fraction