Question

1.45 L of 16°C water is placed in a refrigerator. The refrigerator's motor must supply an extra 10.7 W power to chill the water to 6°C in 0.7 hr. What is the refrigerator's coefficient of performance?

Answer 1

The coefficient of performance of the refrigerator is 2.251.

Step-by-step explanation:

In this case, the coefficient of performance of the refrigerator (
), no unit, is equal to the ratio of the heat rate received from the water to the power needed to work, that is:

(1)

(2)

Where:

- Heat rate received from the water, in watts.

- Power, in watts.

- Density of water, in kilograms per cubic meter.

- Volume of water, in cubic meters.

- Specific heat of water, in joules per kilogram-degree Celsius.

- Temperature change, in degrees Celsius.

- Cooling time, in seconds.

If we know that
,
,
,
,
and
, then the coefficient of refrigeration of the refrigerator is:

The coefficient of performance of the refrigerator is 2.251.