Unformatted text preview: e. The
valve remains open during the process so that the trapped air
also reaches mechanical equilibrium with the atmosphere.
Determine the net heat transfer through the wall of the bottle
and the entropy generation during this filling process.
Answers: 0.5 kJ, 0.0017 kJ/K 7–177 (a) Water flows through a shower head steadily at a
rate of 10 L/min. An electric resistance heater placed in the
water pipe heats the water from 16°C to 43°C. Taking the density of water to be 1 kg/L, determine the electric power input to
the heater, in kW, and the rate of entropy generation during this
process, in kW/K.
(b) In an effort to conserve energy, it is proposed to pass
the drained warm water at a temperature of 39°C through a
heat exchanger to preheat the incoming cold water. If the heat
exchanger has an effectiveness of 0.50 (that is, it recovers only
half of the energy that can possibly be transferred from the
drained water to incoming cold water), determine the electric
power input required in this case and the redu...
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