A High Efficiency Motor Replacement: Reduction in Heat Gain Calculation

What is the reduction in heat gain in the room due to the replacement of a worn-out 75-hp motor with an efficiency of 91.0% by a high-efficiency 75-hp motor with an efficiency of 95.4% under full-load conditions? The reduction in the heat gain is 2.8358 kW.

Calculation of Reduction in Heat Gain:

Given Data:
- Shaft output power of the motor = 75 hp = (75 × 746) = 55950 W
- Efficiency of the original motor = 91.0% = 0.91
- Efficiency of the high-efficiency motor = 95.4% = 0.954

Firstly, we calculate the electric input given to the original motor:

Efficiency of motor = Output Power / Input Power

0.91 = 55950 W / Input Power

Input Power = 55950 W / 0.91 = 61483.5 W = 61.4835 kW

Next, we calculate the electric input given to the high-efficiency motor:

0.954 = 55950 W / Input Power

Input Power = 55950 W / 0.954 = 58647.79 W = 58.6477 kW

Therefore, the reduction in heat gain due to higher efficiency is:

Reduction in Heat Gain = Power Input Original Motor - Power Input High-Efficiency Motor

Reduction in Heat Gain = 61.4835 kW - 58.6477 kW = 2.8358 kW

Conclusion: The reduction in the heat gain in the room due to the replacement of the motor with a higher efficiency is calculated to be 2.8358 kW. This reduction is a result of the increased efficiency of the high-efficiency motor, which requires less power input to operate at the same output power level. This can lead to cost savings and energy efficiency improvements in the system. If you have any further questions or need clarification, please feel free to ask.

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