Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion

The correct answer is: raising the higher temperature.

When the lower temperature of a refrigerating machine is fixed, the coefficient of performance (COP) can be improved by:

Raising the higher temperature: This reduces the temperature difference between the condenser and evaporator, which increases the COP. A smaller temperature difference requires less energy to transfer heat, resulting in a more efficient system.

The other options are not accurate:

- Operating the machine at higher speeds: While increasing the speed can increase the cooling capacity, it also increases the energy consumption, which may not necessarily improve the COP.
- Operating the machine at lower speeds: Reducing the speed can decrease the cooling capacity and may not necessarily improve the COP.
- Lowering the higher temperature: This would increase the temperature difference between the condenser and evaporator, which would decrease the COP.

Note that the COP is a measure of the efficiency of a refrigeration system, defined as the ratio of the cooling capacity to the energy input. Improving the COP can lead to energy savings and reduced operating costs.

The correct answer is: raising the higher temperature.

When the lower temperature of a refrigerating machine is fixed, the coefficient of performance (COP) can be improved by:

Raising the higher temperature: This reduces the temperature difference between the condenser and evaporator, which increases the COP. A smaller temperature difference requires less energy to transfer heat, resulting in a more efficient system.

The other options are not accurate:

- Operating the machine at higher speeds: While increasing the speed can increase the cooling capacity, it also increases the energy consumption, which may not necessarily improve the COP.
- Operating the machine at lower speeds: Reducing the speed can decrease the cooling capacity and may not necessarily improve the COP.
- Lowering the higher temperature: This would increase the temperature difference between the condenser and evaporator, which would decrease the COP.

Note that the COP is a measure of the efficiency of a refrigeration system, defined as the ratio of the cooling capacity to the energy input. Improving the COP can lead to energy savings and reduced operating costs.

Cop= T2/T1-T2.

As the value of T1 is lower, the difference of Temperature is lower so which directly shows an increase in COP.

COP = refrigerating effect/work done.
work done = area enclosed.

So, if the lower temperature is fixed we can only reduce work by lowering the higher temperature and hence increasing the CoP.

I think C is right answer.