OPEN SYSTEMS

Question 1. Name the four forms in which energy enters an open system via the working fluid.

Question 2. Explain the meaning of the term enthalpy.

Question 3. What are the units of:
(a) density
(b) specific volume?

Question 4. Which of the following parameters remain constant throughout a steady flow system?
(a) volumetric flow rate
(b) enthalpy
(c) mass flow rate
(d) internal energy

Question 5. A pipe carries fluid of density of 3 kg m^-3 at a velocity of 20 m s^-1 in a pipe 300 mm diameter. Calculate:
(a) the volumetric flow rate of the fluid
(b) the mass flow rate of the fluid.

Question 6. Air with a density of 2.5 kg m^-3 and internal energy 1800 kJ kg^-1 enters a steady flow system at a pressure of 3 bar. Calculate the enthalpy of the fluid at inlet to the system.

Question 7. An open system develops 5 kW of power. Calculate the work produced per kg of working fluid if the mass flow rate is 200 kg h^-1.

Question 8. State the steady flow energy equation in its specific form.

Question 9. Steam enters a turbine with a velocity of 15 m s^-1 and an enthalpy of 2500 Id kg^-1. It leaves the turbine with a velocity of 30 m s^-1 and an enthalpy of 2000 kJ kg^-1. What is the mass flow rate of fluid required for the turbine to develop a power output of 100 MW if the turbine loses heat to the surroundings at the rate of 50 kJ kg^-1?

Question 10. A compressor receives air at a pressure of 1 bar with a velocity of 30 m s^-1 through a pipe 100 mm diameter, a density of 1.3 kg m^-3 and internal energy of 300 kJ kg^-1. The compressor consumes 100 kW and delivers air at a pressure of 8 bar and internal energy of 500 kJ kg^-1. If the compressor loses heat at the rate of 30 kW and we can consider the exit velocity of the air to be negligible, calculate the density of the air delivered by the compressor.