College

An automotive air conditioner produces a 1-kW cooling effect while consuming 0.75 kW of power. What is the rate at which heat is rejected from this air conditioner?

Answer :

Final answer:

The rate at which heat is rejected from the air conditioner is 1.75 kW, which is the sum of the electrical energy input (0.75 kW) and the cooling effect (1 kW).

Explanation:

To find the rate at which heat is rejected from an air conditioner, we need to apply the principle of energy conservation. The air conditioner is taking in electrical energy and converting part of it into a cooling effect, with the rest being dissipated as heat. The cooling effect is provided by removing heat from the indoor air.

The energy input to the air conditioner is 0.75 kW (this is the electrical power consumed). The cooling effect produced is 1 kW. Since energy cannot be created or destroyed, the heat rejected equals the energy input plus the cooling effect.

The rate of heat rejection can be calculated using the formula:

Heat rejected = Energy input + Cooling effect

Substituting the given values:

Heat rejected = 0.75 kW + 1 kW = 1.75 kW

Therefore, the air conditioner rejects 1.75 kW of heat.

Answer:

The rejected by the air conditioning system is 1.75 kilowatts.

Explanation:

A air conditioning system is a refrigeration cycle, whose receives heat from cold reservoir with the help of power input before releasing it to hot reservoir. The First Law of Thermodynamics describes the model:

[tex]\dot Q_{L} + \dot W - \dot Q_{H} = 0[/tex]

Where:

[tex]\dot Q_{L}[/tex] - Heat rate from cold reservoir, measured in kilowatts.

[tex]\dot Q_{H}[/tex] - Heat rate liberated to the hot reservoir, measured in kilowatts.

[tex]\dot W[/tex] - Power input, measured in kilowatts.

The heat rejected is now cleared:

[tex]\dot Q_{H} = \dot Q_{L} + \dot W[/tex]

If [tex]\dot Q_{L} = 1\,kW[/tex] and [tex]\dot W = 0.75\,kW[/tex], then:

[tex]\dot Q_{H} = 1\,kW + 0.75\,kW[/tex]

[tex]\dot Q_{H} = 1.75\,kW[/tex]

The rejected by the air conditioning system is 1.75 kilowatts.