Q1. A warehouse cold space is maintained at -18 oC by a large R-134a refrigeration cycle. In this cycle, R-134a leaves t

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Q1. A warehouse cold space is maintained at -18 oC by a
large R-134a refrigeration cycle. In this cycle, R-134a leaves the
evaporator as a saturated vapour at -24 °C. The refrigerant enters
the condenser at 1 MPa and leaves at 950 kPa. The compressor has an
isentropic efficiency of 82 % and the refrigerant flowrate through
the cycle is 1.2 kg/s. The temperature outside is 25 oC.
Disregard any heat transfer and pressure drops in the connecting
lines between the units.
a) Sketch a flow diagram of the cycle, labelling each
device, indicating where heat and work flows into, or out of, the
system, and the direction of flow of the refrigerant. Number your
streams, starting with 1 at outlet of the compressor and label with
values given from the question description above.
b) Show the cycle (approximately) on
a T-s diagram with respect to saturation lines. Number
points in the cycle the same as part (a), show the direction of the
cycle and where energy transfers into, or out of, the cycle.
c) What are three ways to reduce the energy consumption of
an industrial freezer? These measures can be part of the design or
the operation of the freezer. [Note: the freezer must operate at no
higher temperature than -18 oC due to food regulations.]