Q$3)$ a$)$ & b$)$

The COP and the refrigeration rate of a refrigerator are given. The power consumption of the refrigerator is to be determined.

Assumptions The refrigerator operates steadily.

Analysis Since the refrigerator runs one$-$fourth of the time and removes heat from the food compartment at an average rate of $800k\frac{J}{h},$ the refrigerator removes heat at a rate of

$Q_L^{}=$

when running. Thus the power the refrigerator draws when it is running is

$W_{\text{n}\text{e}\text{t}\text{i}\text{o}\text{n}}^{}=\frac{Q_R^{}}{CO{P}_R}$

The diffuser in a jet engine is designed to decrease the kinetic energy of the ait entering the engine compressor without any work or heat interactions. Galcula the velocity at the exit of a diffuser when air at $100$ kPa and $30C$ enters it with velocity of $350\frac{m}{s}$ and the exit state is $200$ kPa and $90C.$

$P_1=100$kPa

$T_1=30C$

$v_1=350\frac{(m)}{(s)}$

$P_2=200$kPa

$T_2=90C$