Question

3. Consider a dual-loop cycle utilizing air as the working fluid is shown schematically in the figure below. Air enters the compressor at 1 bar and 4°C and is compressed to 3 bar. Part of the air exiting the compressor enters the refrigeration cycle and remaining enters the power cycle. The air supplied to the refrigeration cycle from the compressor is cooled to the 55°C at constant pressure in a heat exchanger and then expands in a turbine to 1 bar. This low temperature air absorbs the cooling load at constant pressure before re-entering the compressor. The compressor is run by the turbines; all the power generated by the turbine of the refrigeration cycle and the turbine of the power cycle are supplied to the compressor. Air enters the turbine of the power cycle at 3 bar and exits at 1 bar. Air supplied to the power cycle is heated in the heater using fuel with heating value of 42,700 kJ/kg; the air to fuel mass ratio is 90 kg/kg. The mass flowrate of air through the power cycle is 1 kg/s. Air exiting the turbine of the power cycle is cooled before it re-enters the compressor. Take 1 bar 105 N/m2, T(°K)-273 T(C), and 1 atm -105 Pa. Assume air to be an ideal gas (Cp- 1.004 kJ/kg K and k-1.4) determine the following. Determine: a. T-s diagram of the cycle (2 points) b. Mass flowrate through the refrigeration cycle (2 points) c. Thermal efficiency of the power cycle (2 points) d. COP of the refrigeration loop (2 points) e. Heat rejected from the combined cycle (2 points) HE 2 6 1 HE T: Turbine, C: Compressor, HE: Heat exchanger, H: Heater, R: Heat rejection

Answer 1

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3 P3 Tu、= 622, 247, alant e Giuen (.mp 4-肉ls 。 (328-237, b36) +(3S('6737-622-247)-(Hrna) 31949-277 Mo' (13-776) 127, 3067 =

le. tGienC th 472.5S 345 247 472.S5 26 , 94 % d> cop of Ro lop 37 36 5 I4 37 36 2 7122 Re Je Combined cycle

nceo Riredta! Total -