Question

An inventor claims to have developed a food freezer that at steady state requires a power input of 0.25 kW to extract energy by heat transfer at a rate of 3000 J/s from freezer contents at 270 K. Investigate this claim for an ambient temperature of 293 K.

Answer 1

Answer:

investor claim is acceptable

Explanation:

given data

Win = 0.25 kW

Qc = 3000 J/s = 3kW

Th = 293 K

Tc = 270 K

solution

we get here coefficient of performance of cycle is

coefficient of performance = $\frac{Qc}{Win}$    ..................1

put here value and we get

coefficient of performance = $\frac{3}{0.25}$  

coefficient of performance = 1.2

and

coefficient of performance of ideal refrigeration is

coefficient of performance = $\frac{Tc}{Th-Tc}$    ..................2

coefficient of performance = $\frac{270}{293-270}$  

coefficient of performance = 11.74

and

we can see here that coefficient of performance of ideal refrigeration  is is more than real cycle coefficient of performance

so investor claim is acceptable