Consider an electric motor with a shaft power output of 20 kW and an efficiency of 88 percent. Determine the rate at which the motor dissipates heat to the room it is in when the motor operates at full load. In winter, this room is normally heated by a 2-kW resistance heater. Determine if it is necessary to turn the heater on when the motor runs at full load. (Page 96).

Question

Aylin Case

Engineering

14 April, 20:28

Consider an electric motor with a shaft power output of 20 kW and an efficiency of 88 percent. Determine the rate at which the motor dissipates heat to the room it is in when the motor operates at full load. In winter, this room is normally heated by a 2-kW resistance heater. Determine if it is necessary to turn the heater on when the motor runs at full load. (Page 96).

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Answers (1)

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Hubbard · Answer 1

Rate of heat dissipation = 2.4 kW,

When the engine operates at complete load, it would not be essential to switch the heater on. As, the level of engine heat dissipation is higher than the heat dissipation level per heater.

Explanation:

The rate of heat dissipation = (total / output / power / times (1 - efficiency))

Rate of heat dissipation = 20 kW (1-0.88)

Rate of heat dissipation = 2.4 kW,

For, room heating if heat required is 2 kW,

Then,

When the engine operates at complete load, it would not be essential to switch the heater on. As, the level of engine heat dissipation is higher than the heat dissipation level per heater.