Assignment $2$

Consider a two$-$stage compression refrigeration system operating between the

pressure limits of $0\mathrm{.}8$ and $0\mathrm{.}14$ MPa $.$ The working fluid is refrigerant$-134$a$.$

The refrigerant leaves the condenser as a saturated liquid and is throttled to

a flash chamber operating at $0\mathrm{.}32$ MPa $.$ Part of the refrigerant evaporates

during this flashing process, and this vapor is mixed with the refrigerant

leaving the low$-$pressure compressor. The mixture is then compressed to the

condenser pressure by the high$-$pressure compressor. The liquid in the flash

chamber is throttled to the evaporator pressure and cools the refrigerated

space as it vaporizes in the evaporator. Assuming the refrigerant leaves the

evaporator as a saturated vapor and both compressors are isentropic$,$ deter$-$

mine $($a$)$ the fraction of the refrigerant that evaporates as it is throttled to

the flash chamber, $($b$)$ the amount of heat removed from the refrigerated

space and the compressor work per unit mass of refrigerant flowing through

the condenser, and $($c$)$ the coefficient of performance.