7. A gas refrigeration system as shown in Fig.??, using air as the working fluid has a pressure ratioof 5. Air enters the compressor at 0 °C. The high pressure air is cooled to 35 °C by rejectingheat to the surroundings. The refrigerant leaves the turbine at -80 °C and then it absorbs heatfrom the refrigerated space before entering the regenerator. The mass flow rate of air is 0.4 kg/s.Assuming isentropic efficiencies of 80 % for the compressor and 85 % for the turbine and usingconstant specific heats at room temperature, determine0.434]21.4 kW0.48(a) the effectiveness of the regenerator,(b) the rate of heat removal from the refrigerated space,(c) the COP of the cycle, and(d) the refrigeration load and the COP if this system operated on the simple gas refrigeration cycleUse the same compressor inlet temp. as given, the same turbine inlet temperature as calculated,27.7 kW, 0.599and the same compressor and turbine efficiencies.

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Asked Nov 12, 2019
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7. A gas refrigeration system as shown in Fig.??, using air as the working fluid has a pressure ratio
of 5. Air enters the compressor at 0 °C. The high pressure air is cooled to 35 °C by rejecting
heat to the surroundings. The refrigerant leaves the turbine at -80 °C and then it absorbs heat
from the refrigerated space before entering the regenerator. The mass flow rate of air is 0.4 kg/s.
Assuming isentropic efficiencies of 80 % for the compressor and 85 % for the turbine and using
constant specific heats at room temperature, determine
0.434]
21.4 kW
0.48
(a) the effectiveness of the regenerator,
(b) the rate of heat removal from the refrigerated space,
(c) the COP of the cycle, and
(d) the refrigeration load and the COP if this system operated on the simple gas refrigeration cycle
Use the same compressor inlet temp. as given, the same turbine inlet temperature as calculated,
27.7 kW, 0.599
and the same compressor and turbine efficiencies.
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7. A gas refrigeration system as shown in Fig.??, using air as the working fluid has a pressure ratio of 5. Air enters the compressor at 0 °C. The high pressure air is cooled to 35 °C by rejecting heat to the surroundings. The refrigerant leaves the turbine at -80 °C and then it absorbs heat from the refrigerated space before entering the regenerator. The mass flow rate of air is 0.4 kg/s. Assuming isentropic efficiencies of 80 % for the compressor and 85 % for the turbine and using constant specific heats at room temperature, determine 0.434] 21.4 kW 0.48 (a) the effectiveness of the regenerator, (b) the rate of heat removal from the refrigerated space, (c) the COP of the cycle, and (d) the refrigeration load and the COP if this system operated on the simple gas refrigeration cycle Use the same compressor inlet temp. as given, the same turbine inlet temperature as calculated, 27.7 kW, 0.599 and the same compressor and turbine efficiencies.

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Expert Answer

Step 1

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First calculate the temperature at the compressor exit,

The isentropic temperature at the compressor exit

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Р. T2 T Р 1.4- Ty= (273+0) (5) = 432.38K Isentropic efficiency of the compressor is given as 80%, this can be used to calculate the actual temperature at the compressor exit -T Т, — Т, h-h 432.38-273 0.8 Т, — 273 T 472.22K

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Step 2

The temperature at the turbine exit can be calculated from the isentropic relation and the turbine efficiency

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Р. Т, 3DТ, 4 Р. 4 1.4- 14 1 T =T 5 The turbine efficiency is 85%, from this h-hT-T h-h T-T 4 Т, —193 0.85 14-1 114 Т, -Т, 5 Т, - 193 T -0.6317 0.85= 193 1- 0.85 1-0.631 T 281.2K

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Step 3

Now, balance the energy of regenerator to calculate the...

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тс, (7, -Т.) - тс, (Т -т,) (Т,-т.) - (Т-Т,) (308- 281.2) - (273-Т,) Т, %3D246.2K

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