Steam (9bar and 200°C) enters an insulated nozzle with a velocity of 50m/s. It leaves at a
pressure 1,5bar and a velocity 560m/s. Determine the exit temperature of the steam and the
steam quality (steam fraction) and isentropic efficiency. Use tables for this problem!
A solid vessel (2m³) contains a mixture of steam and water at pressure of 200kPa. The
steam fraction is 70% How much heat in [kJ] must be delivered to the mixture to reach the
final pressure of 700kPa? Which is the final temperature?
Calculate the properties of moist air. P=1bar, dry bulb T=20°C, humidity ratio=0,006
Calculate specific volume and specific enthalpy by using Psychrometric chart (2p)
Calculate specific enthalpy and specific entropy by assuming Ideal mixture of air
and H2O (3p)
Calculate specific enthalpy and specific entropy by assuming Ideal mixture of N2,
O2 (N2/02=4/1 volume ratio) and H2O (4p)
Clue: Volume ratio = mole ratio
Answer the following questions:
Explain why a process that violet the 2nd law may not violate the 1= law of
Explain why heat can NOT be 100% convert to work (2p)
Explain the impacts of the ambient temperature on the Carnot efficiency of
refrigeration and heat pump cycles (4p)
Pls note: you cannot copy/paste anything from any source You have to answer with
your own words Plagiarism will also be checked
2 kg air performs a counterclockwise process in a piston-cylinder assembly due to:
1-2: Isochoric from (V, P1 to V2
2-3: Isobaric expansion from pressure p2 to V3
3->1: Isothermal compression back to p
V2=2m³, p==100kPa and V2=10m³
Sketch the process in ap-V-diagram
1. (3p) Calculate the temperature during the isothermal process
2. (3p) Calculate the net work Wn. for the process! Is it net work input or net work
3. (4p) Calculate the heat amounts Qu, a and Q2,
6: An operating ideal Otto Cycle works with air (2,5kg). At the inlet of the engine the
pressure is 1bar and the temperature is 300K. After the compression the pressure is
15bar and after the heat delivery the temperature is 2100K. Calculate:
1. (2p) The pressure after the heat delivery
2. (3p) The heat delivery in the cycle
3. (3p) The heat extraction in the cycle
4. (1p) The thermal efficiency of the cycle
The states are given before (25bar, 400°C) and after (0,25bar, x=98%) a well isolated
steam turbine (neglect potential and kinetic energies): x= steam fraction
The turbine delivers shaft power (3MW)
1. (2p) The turbine isentropic efficiency
2 (3p) Mass flow through the turbine
A cooling unit works with the refrigerant (R134a). The unit works between the pres-
sure levels 1,4 bars and 7,5 bars. The compressor input power is given (30kW). After
the evaporator the refrigerant is superheated by 8°C and the compressor isentropic
efficiency is 70% After the condenser the refrigerant is subcooled by 3°C.
1. (2p) Which are the evaporation- and condensation temperatures?
2 (2p) What is the mass flow in the process?
3. (2p) What is the cooling power?
4. (1p) What is the temperature after the compressor?
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