Problem 1

Problem 1In a gas turbine unit, the gases flow through the turbine is 15 kg/s and the power developed by the turbine is 12000 kW. The enthalpies of gases at the inlet and outlet are 1260 kJ/kg and 400 kJ/kg respectively, and the velocity of gases at the inlet and outlet are 50 m/s and 110 m/s respectively. Calculate :(i) The rate at which heat is rejected to the turbine, and(ii) The area of the inlet pipe given that the specific volume of the gases at the inlet is 0.45 m3/kg.Problem 2Steam at a 6.87 bar, 205C, enters in an insulated nozzle with a velocity of 50 m/s. It leaves at a pressure of 1.37 bar and a velocity of 500 m/s.Determine the final enthalpy of steam.Problem 3The working fluid, in a steady flow process flows at a rate of 220 kg/min. The fluid rejects 100 kJ/s passing through the system. The conditions of the fluid at inlet and outlet are given as : C1 = 320 m/s, p 1 = 6.0 bar, u1 = 2000 kJ/kg, v1 = 0.36 m3/kg and C 2 = 140 m/s, p2 = 1.2 bar, u2 = 1400 kJ/kg, v2 = 1.3 m3/kg. The suffix 1 indicates the condition at inlet and 2 indicates at outlet of the system.Determine the power capacity of the system in MW.The change in potential energy may be neglected.

Problem 412 kg of air per minute is delivered by a centrifugal air compressor. The inlet and outlet conditions of air are C1 = 12 m/s, p1 = 1 bar, v1 = 0.5 m3/kg and C2 = 90 m/s, p2 = 8 bar, v2 = 0.14 m3/kg. The increase in enthalpy of air passing through the compressor is 150 kJ/kg and heat loss to the surroundings is 700 kJ/min.Find : (i) Motor power required to drive the compressor ;(ii) Ratio of inlet to outlet pipe diameter.

Assume that inlet and discharge lines are at the same level.

Problem 5A centrifugal pump delivers 50 kg of water per second. The inlet and outlet pressures are 1 bar and 4.2 bar respectively. The suction is 2.2 m below the centre of the pump and delivery is 8.5 m above the centre of the pump. The suction and delivery pipe diameters are 20 cm and 10 cm respectively.Determine the capacity of the electric motor to run the pump.

Problem 6A rigid cylinder of volume 0.028 m3 contains steam at 80 bar and 350C. The cylinder is cooled until the pressure is 50 bar. Calculate :(i) The state of steam after cooling ;(ii) The amount of heat rejected by the steam.

Problem 70.08 kg of dry steam is heated at a constant pressure of 2 bar until the volume occupied is 0.10528 m3. Calculate :(i) Heat supplied ;(ii) Work done.

Problem 8Steam at 7 bar and dryness fraction 0.95 expands in a cylinder behind a piston isothermally and reversibly to a pressure of 1.5 bar. The heat supplied during the process is found to be 420 kJ/kg. Calculate per kg :(i) The change of internal energy ;(ii) The change of enthalpy ;(iii) The work done.

Problem 9In a steam engine cylinder the steam expands from 5.5 bar to 0.75 bar according to a hyperbolic law, pv = constant. If the steam is initially dry and saturated, calculate per kg of steam :(i) Work done ;(ii) Heat flow to or from the cylinder walls.

Problem 101 kg of steam at 120 bar and 400C expands reversibly in a perfectly thermally insulated cylinder behind a piston until the pressure is 38 bar and the steam is then dry saturated. Calculate the work done by the steam.

Problem 11In a steam engine the steam at the beginning of the expansion process is at 7 bar, dryness fraction 0.98 and expansion follows the law pv1.1 = constant, down to a pressure of 0.34 bar. Calculate per kg of steam (i) The work done during expansion ;(ii) The heat flow to or from the cylinder walls during the expansion.

Problem 12 Steam enters a steam turbine at a pressure of 15 bar and 350C with a velocity of 60 m/s. The steam leaves the turbine at 1.2 bar and with a velocity of 180 m/s. Assuming the process to be reversible adiabatic, determine the work done per kg of steam flow through the turbine.Neglect the change in potential energy.

Problem 13Steam at 10 bar and 200C enters a convergent divergent nozzle with a velocity of 60 m/s and leaves at 1.5 bar and with a velocity of 650 m/s. Assuming that there is no heat loss, determine the quality of the steam leaving the nozzle.