A commercial office building is located in the city of Lansing, Michigan, and is heatedusing a gaseous fuel with a heating value of 725 Btu/std ft3. The indoor designtemperature is 71ºF. The heat load for the building is known to be 250,000 Btu/hr. Thisheat load accounts for the fact that there are internal heat gains in the building, due tothe presence of people and electronic equipment (e.g., lights and radios). People in thebuilding are usually seated and involved in light activity.a) The furnace had an initial efficiency factor of 73% when installed, but since thenefficiency-improvement retrofits were implemented that raised the efficiency factorto its present value of 82%. The building was designed using the 99% designheating temperature value for the city to determine the outdoor design temperature.Evaluate the annual fuel quantity (in std ft3) required to heat the building, using thedegree-day or bin method.b) Seventy people use the building, but the occupancy pattern for the building variesthroughout the day. Sixty of the people who use the building arrive at 7:30 a.m. andleave at 5:00 p.m. Ten people work part time, with seven of these arriving at 11:45a.m. and leaving at 5:00 p.m., and three of these people arriving at 3:00 p.m. andleaving at 7:30 p.m. The internal heat gain in the building due to the operation ofequipment is constant throughout the day and night at 20,000 Btu/hr, and is entirely sensible in nature. Determine the sensible and latent internal heat gains (in Btu/hr)in the building at the following three times: 4:00 p.m., 8:00 p.m. and at 5:00 a.m.
A commercial office building is located in the city of Lansing, Michigan, and is heated
using a gaseous fuel with a heating value of 725 Btu/std ft3
. The indoor design
temperature is 71ºF. The heat load for the building is known to be 250,000 Btu/hr. This
heat load accounts for the fact that there are internal heat gains in the building, due to
the presence of people and electronic equipment (e.g., lights and radios). People in the
building are usually seated and involved in light activity.
a) The furnace had an initial efficiency factor of 73% when installed, but since then
efficiency-improvement retrofits were implemented that raised the efficiency factor
to its present value of 82%. The building was designed using the 99% design
heating temperature value for the city to determine the outdoor design temperature.
Evaluate the annual fuel quantity (in std ft3
) required to heat the building, using the
degree-day or bin method.
b) Seventy people use the building, but the occupancy pattern for the building varies
throughout the day. Sixty of the people who use the building arrive at 7:30 a.m. and
leave at 5:00 p.m. Ten people work part time, with seven of these arriving at 11:45
a.m. and leaving at 5:00 p.m., and three of these people arriving at 3:00 p.m. and
leaving at 7:30 p.m. The internal heat gain in the building due to the operation of
equipment is constant throughout the day and night at 20,000 Btu/hr, and is entirely sensible in nature. Determine the sensible and latent internal heat gains (in Btu/hr)
in the building at the following three times: 4:00 p.m., 8:00 p.m. and at 5:00 a.m.
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