Consider an electric motor with a shaft power output of 22.5 kW and an efficiency of 85%. 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 2.5 kW resistance heater. Determine if it is necessary to turn the heater on when the motor runs at full load.

Rate of heat dissipation = 3.375 Kw

Explanation:

Given:

Old power output (Heat) = 22.5 Kw

Efficiency = 85% = 0.85

New power output (Heat) = 2.5 Kw

Find:

Rate of heat dissipation = ?

Computation:

Rate of heat dissipation = Total output power ( 1 - Efficiency)

Rate of heat dissipation = 22.5 Kw (1 - 0.85)

Rate of heat dissipation = 3.375 Kw

So, room heating if heat required is 2.5 Kw  then ,

It will not be necessary to turn the heater on.

Rate of heat dissipation by electric motor is greater than rate of heat dissipation by heater.

gets less