Note: You will be required to use data from the NIST Webbook $($found here$)$ for appropriate properties to

solve the problem. A "tutorial video" for using the Webbook has also been uploaded in this week's content.

Consider the cycle described below, where ammonia is used as the working fluid:

$2\mathrm{.}74mo\frac{l}{s}$ of air, initially at $36\mathrm{.}0C,$ is passed through the shell side of a heat exchanger, with $5\mathrm{.}00$ kg$/$hr of ammonia flowing through the tubes. There is no mixing of the streams.

The ammonia leaves the heat exchanger as a saturated vapour before entering a compressor, where

the pressure is raised to $5\mathrm{.}00$ bar, producing a superheated vapour

The superheated vapour enters a poorly designed isobaric cooler that drops the temperature to $0\mathrm{.}0C$

The resulting liquid stream is throttled through a valve, with a pressure gauge on the outlet reading

$1\mathrm{.}00$ bar $($atmospheric pressure is $1\mathrm{.}013$ bar$).$ The resulting two$-$phase mixture is fed to the heat

exchanger to complete the cycle.

You are investigating the viability of replacing the valve with a reversible turbine in the hope of harvesting

some of the energy avalable when expanding the ammonia. A schematic of the original process is provided

below. If the heat exchanger operates adiabatically, what is the temperature of the exiting air? The next questions consider the case of replacing the valve with a turbine. You design the turbine in such a way that the ammonia still leaves the turbine at $1\mathrm{.}00$ bar gauge. What is the entropy of the stream entering the turbine? Remembering the isentropic operation of the turbine, and using an energy balance over the unit, what is the quality of the stream leaving the turbine? If the heat exchanger operates adiabatically, what is the temperature of the exiting air? How much work could be extracted from the turbine $($remember the sign$)?$