Termo II Uas 2013_036
1
Ujian Akhir Semester JurusanTeknik Mesin Undip Mata Kuliah : ThermodinamikajL Dosen : Dr. Ir. Eflita Yohana, MT Hari/Tanggai : Jumaat, 5 Juli 2013 Waktu : 100 menit Sifat : Closed Book cut o9 xoKxi 5 S 1. An ideal diesel engine has a compression ratio of 20 and uses air as the working fluid. The state of air at the beginning of the compression process is 95 kPa and 20°C. I f the maximum temperature in the cycle is not to exceed 2200 K, detennine (a) the thermal efficiency and (b) the mean effective pressure. Assume constant specific heats for air at room temperature (c) Determine the thermal efficiency. 2. A gas-turbine power plant operates on the simple Brayton cycle with air as the working fluid and delivers 32 MW of power. The minimum and maximum temperatures in the cycle are 310 and 900 K, and the pressure of air at the compressor exit is 8 times the value at the compressor inlet. Assuming an isentropic efficiency of 80 percent for the compressor and 86 percent for the turbine, determine the mass flow rate of air through the cycle. Account for the variation of specific heats with temperature. s 3. A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at - 30°C by rejecting its waste heat to cooling water that enters the condenser af 18°C at a rate of 0.25 kg/s and leaves at 26°C. The refrigerant enters the condenser at 1.2 MPa and 65°C and leaves at 42°C. The inlet state of the compressor is 60 kPa and - 34°C and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine (a) the quality of the refrigerant at the evaporator inlet, (b) the refrigeration load, (c) the COP of the refrigerator, and (d) the theoretical maximum refrigeration load for the same power input to the compressor. 4. A 5m X 5m X 3m, contains air at 25°C and lOOkPa at a relative humidity of 75 percent. Determine (a) the partial pressure of dry air, (b) the specific humidity, (c) the enthalpy per unit mass of the dry air, and (d) the masses of the dry air and water vapor in the room 5 a .Apa yang di sebut dengan Relatif humidity b. Apa yang di sebut dengan Humidity Ratio c. Apa yang di sebut dengan dew point temperatur Selamat Bekerja
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Transcript of Termo II Uas 2013_036
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Ujian Akhir Semester JurusanTeknik Mesin Undip Mata Kuliah : ThermodinamikajL
Dosen : Dr. Ir. Eflita Yohana, MT Hari/Tanggai : Jumaat, 5 Juli 2013
Waktu : 100 menit Sifat : Closed Book
cut o9 xoKxi 5 S
1. An ideal diesel engine has a compression ratio of 20 and uses air as the working fluid. The state of air at the beginning of the compression process is 95 kPa and 20C. I f the maximum temperature in the cycle is not to exceed 2200 K, detennine (a) the thermal efficiency and (b) the mean effective pressure. Assume constant specific heats for air at room temperature (c) Determine the thermal efficiency.
2. A gas-turbine power plant operates on the simple Brayton cycle with air as the working fluid and delivers 32 MW of power. The minimum and maximum temperatures in the cycle are 310 and 900 K, and the pressure of air at the compressor exit is 8 times the value at the compressor inlet. Assuming an isentropic efficiency of 80 percent for the compressor and 86 percent for the turbine, determine the mass flow rate of air through the cycle. Account for the variation of specific heats with temperature.
s
3. A commercial refrigerator with refrigerant-134a as the working fluid is used to keep the refrigerated space at - 30C by rejecting its waste heat to cooling water that enters the condenser af 18C at a rate of 0.25 kg/s and leaves at 26C. The refrigerant enters the condenser at 1.2 MPa and 65C and leaves at 42C. The inlet state of the compressor is 60 kPa and - 34C and the compressor is estimated to gain a net heat of 450 W from the surroundings. Determine (a) the quality of the refrigerant at the evaporator inlet, (b) the refrigeration load, (c) the COP of the refrigerator, and (d) the theoretical maximum refrigeration load for the same power input to the compressor.
4. A 5m X 5m X 3m, contains air at 25C and lOOkPa at a relative humidity of 75 percent. Determine (a) the partial pressure of dry air, (b) the specific humidity, (c) the enthalpy per unit mass of the dry air, and (d) the masses of the dry air and water vapor in the room
5 a .Apa yang di sebut dengan Relatif humidity b. Apa yang di sebut dengan Humidity Ratio c. Apa yang di sebut dengan dew point temperatur
Selamat Bekerja
