A fan is to accelerate quiescent air to a velocity of 10 m/s at a rate of 4 m3/s. Determine the minimum power that must be supplied to the fan. Take the density of air to be 1.18 kg/m3.
a. A fan is to accelerate quiescent air to a velocity of 10
m/s at a rate of 4 m3/s. Determine the minimum power that
must be supplied to the fan. Take the density of air to be 1.18
kg/m3.
b. A classroom that normally contains 40 people is to
be air-conditioned with window air-conditioning units of 5-
kW cooling capacity. A person at rest may be assumed to
dissipate heat at a rate of about 360 kJ/h. There are 10 lightbulbs in the room, each with a rating of 100 W. The rate of
heat transfer to the classroom through the walls and the windows is estimated to be 15,000 kJ/h. If the room air is to be
maintained at a constant temperature of 21°C, determine the
number of window air-conditioning units required
c. A vertical piston–cylinder device contains water and
is being heated on top of a range. During the process, 65 Btu of heat is transferred to the water, and heat losses from the
side walls amount to 8 Btu. The piston rises as a result of
evaporation, and 5 Btu of work is done by the vapor. Determine the change in the energy of the water for this process.
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