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Steam at 5 bar and 250 Deg is contained in
a rigid vessel of volume 2.2 m, The vessel
is cooled until the steam is just dry saturated.
Calculate the heated rejected, the change in
entropy, the final pressure and the mass of
the steam.
A mass of 0.05 kg of a perfect gas with a
molar mass of 70 kg/kmol, occupying a
volume of 0.03 m at 1.025 bar,
is
compressed
reversibly until the pressure is
6.15 bar. Calculate the final temperature, the
work done on the prefect gas and the heat
supplied:
I. When the process is according to a law
II. When the process is isothermal
II. When the process takes place in a
perfectly thermally insulated cylinder
Take cy = 395.93 J/kg.K
If 10-7 J of heat is added to a system w is so large that its temperature () /" does not change, by what factor will the number of accessible states of the system increase if the temperature is 30 K?
The power developed by a gas turbine is 15000 kW. Gases flow through the turbine of the gas turbine unit at 20 kg/s. The specific enthalpies of the gases at the inlet and the outlet of the turbine are 1300 kJ/kg and 400 kJ/kg respectively. The velocities of the gases at the inlet and the outlet are 65 m/s and 155 m/s respectively.
(a) Draw a schematic diagram of the turbine and label the flows in and out of it. (2 marks)
(b) What is the purpose of a gas turbine? How does irreversibility affect the performance of a gas turbine? (4 marks)
(c) Explain the equation which can be used to assess changes in energy in the turbine. (3 marks)
(d) Calculate the rate at which heat is rejected from the turbine. (11 marks)
(e) Calculate the area of the turbine inlet pipe if the specific volume of the gases at inlet is 0.6 m3 /kg. (5 marks)
1. (a) Explain what is meant by a reversible process. Why are real processes not reversible? (5 marks)
(b) A cylinder contains a unit mass of a fluid. The initial pressure is 10 bar and the initial volume is 0.03 m^3 . The fluid expands reversibly behind a piston according to the equation pV^2 = constant until the volume is doubled. The fluid is then cooled reversibly at constant pressure until the piston goes back to its initial position. Heat is then supplied with the piston firmly locked in position until the pressure increases and reaches the initial value of 10 bar.
(i) Sketch the cycle on a labelled pressure-volume diagram. (5 marks)
(ii) Calculate the net work done by the fluid. (15 marks)
a.What is meant by reversible process?
a. A certain tractor is said to be capable of pulling with a steady force of 18kN while moving at a velocity of 8.0m/s. How much power in kilowatts and in horsepower is the tractor developing under these conditions?
1. A human tissue cell has a diameter of the order 1.0µm. Assuming each cell occupies a cube of 1.0 µm on one side, estimate the number of cells in 1.0cm3 of tissue.
Heliox, a breathing gas composed of a mixture of helium (He) and oxygen (O₂), is used medically for treatment in acute asthma. In medicine heliox may refer to a mixture of 21% O2 (the same as air) and 79% He. Calculate the average molar mass and density of heliox at pressure Patm = 100 kPa and room temperature t = 22°C. The molar mass of oxygen is po 16 and helium He = 4 g/mole.
1. It is given that three moles of helium gas are at a temperature of 32 °C and at a pressure of 15 atm. Helium gas is heated while being at a constant volume container. As a result, the pressure of gas triples. what is the final temperature of it
