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When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by
- a)operating the machine at higher speeds
- b)operating the machine at lower speeds
- c)raising the higher temperature
- d)lowering the higher temperature
Correct answer is option 'D'. Can you explain this answer?
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When the lower temperature of a refrigerating machine is fixed, then t...
When the lower temperature of a refrigerating machine is fixed, the coefficient of performance can be improved by lowering the higher temperature. This means that the temperature at which heat is rejected by the refrigerating machine should be decreased.
Lowering the higher temperature helps to improve the coefficient of performance of a refrigerating machine due to the following reasons:
1. Carnot Efficiency: The coefficient of performance of a refrigerating machine is defined as the ratio of the desired cooling effect to the work input. According to the Carnot cycle, the maximum efficiency of a heat engine is determined by the temperature difference between the hot and cold reservoirs. By lowering the higher temperature, the temperature difference between the hot and cold reservoirs decreases, resulting in an increase in the efficiency of the refrigerating machine.
2. Heat Transfer: Heat transfer is directly proportional to the temperature difference between the hot and cold reservoirs. By lowering the higher temperature, the temperature difference decreases, reducing the amount of heat that needs to be rejected by the refrigerating machine. This leads to a decrease in the energy consumption and an improvement in the coefficient of performance.
3. Compressor Work: The work required by the compressor in a refrigerating machine is directly proportional to the temperature difference between the evaporator and condenser. By lowering the higher temperature, the temperature difference decreases, reducing the work required by the compressor. This results in an increase in the coefficient of performance.
In summary, when the lower temperature of a refrigerating machine is fixed, the coefficient of performance can be improved by lowering the higher temperature. This leads to an increase in efficiency, a decrease in energy consumption, and a reduction in the work required by the compressor.
Lowering the higher temperature helps to improve the coefficient of performance of a refrigerating machine due to the following reasons:
1. Carnot Efficiency: The coefficient of performance of a refrigerating machine is defined as the ratio of the desired cooling effect to the work input. According to the Carnot cycle, the maximum efficiency of a heat engine is determined by the temperature difference between the hot and cold reservoirs. By lowering the higher temperature, the temperature difference between the hot and cold reservoirs decreases, resulting in an increase in the efficiency of the refrigerating machine.
2. Heat Transfer: Heat transfer is directly proportional to the temperature difference between the hot and cold reservoirs. By lowering the higher temperature, the temperature difference decreases, reducing the amount of heat that needs to be rejected by the refrigerating machine. This leads to a decrease in the energy consumption and an improvement in the coefficient of performance.
3. Compressor Work: The work required by the compressor in a refrigerating machine is directly proportional to the temperature difference between the evaporator and condenser. By lowering the higher temperature, the temperature difference decreases, reducing the work required by the compressor. This results in an increase in the coefficient of performance.
In summary, when the lower temperature of a refrigerating machine is fixed, the coefficient of performance can be improved by lowering the higher temperature. This leads to an increase in efficiency, a decrease in energy consumption, and a reduction in the work required by the compressor.
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When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved bya)operating the machine at higher speedsb)operating the machine at lower speedsc)raising the higher temperatured)lowering the higher temperatureCorrect answer is option 'D'. Can you explain this answer?
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