Assignment-I Thermal Systems (Unit-I).pdf

ASSIGNMENT-1 1. 10 kg of air is heated in a rigid vessel from 20°C to 100°C. If the ratio of specific heat is 1.4, estimate the values of Cp and Cv, change in internal energy, and enthalpy. 2. In a throttling calorimeter, the steam is admitted at 10 bar, it is th...

ASSIGNMENT-1 1. 10 kg of air is heated in a rigid vessel from 20°C to 100°C. If the ratio of specific heat is 1.4, estimate the values of Cp and Cv, change in internal energy, and enthalpy. 2. In a throttling calorimeter, the steam is admitted at 10 bar, it is throttled to atmospheric pressure and 110°C. Determine the dryness fraction of steam. Assume the specific heat of superheated steam as 2.2 kJ/kg K. State 1, 10 bar:- hf1 = 762.81 kJ/kg; hfg1 = 2014.3 kJ/kg; State 2, 1.01325 bar:- hg2 = 2676 kJ/kg; Tsat2 = 100°C 3. ln an experiment, a sample of wet steam is passed through a separating calorimeter. At some instant, the mass of water collected in the separator Nwas 0.2 kg, while the amount of steam condensed was found to be 2.5 kg. Determine the dryness fraction of steam entering the calorimeter. 4. Calculate volume, density, enthalpy, and entropy of 2 kg of water at 2 bar and 80°C. At 80°C, the specific volume of water vf = 0.001029 m3/kg. 5. Calculate volume, density, enthalpy and entropy of 2 kg of steam at 80°C and having a dryness fraction of 0.85. Properties of water At 80°C; psat = 47.39 kPa; vf = 0.001029 m3/kg; vg = 3.40715 m3/kg; hf = 334.88 kJ/kg hfg = 2308.77 kJ/kg K sf = 1.0752 kJ/kg K sfg = 6.5369 kJ/kg K. 6. A certain boiler generates 1000 kg of steam per hour at 10 bar and 0.97 dry. This steam is then taken to a superheater and is heated to a temperature of 280°C keeping the pressure constant. The feed water is available at 30°C. Find (a) Heat supplied per hour in the boiler, (b) Heat supplied per hour in the superheater, (c) Internal energy of superheated steam, (d) Change in internal energy of steam. The properties of steam at 10 bar; Tsat = 179.91°C hf = 762.81, kJ/k hfg = 2014.3 kJ/kg vg = 0.19444 m3/kg vf = 0.001127 m3/kg hg = 2777.08 kJ/kg. 7. A vessel of volume 0.04 m3 contains a mixture of saturated water and saturated steam at a temperature of 250°C. The mass of the liquid present is 9 kg. Find the pressure, the mass. the specific volume, the enthalpy, the entropy, and the internal energy. Water At 250°C; psat = 3.973 MPa ; vf = 0.0012512 m3/kg; vg = 0.05013 m3/kg; hf = 1085.36 kJ/kg hfg = 1716.2 kJ/kg K sf = 2.7927 kJ/kg K sfg = 3.2802 kJ/kg K. 8. Define dryness fraction and state various methods of determination of dryness fraction. 9. Prove that for a constant pressure process, dq = dh. 10. Draw the phase equilibrium diagram for a pure substance on T-s plot with relevant constant property lines. 11. Draw the phase equilibrium diagram for a pure substance on h-s plot with relevant constant property lines. 12. What is qu11liry of steam? What are the different methods of measurement of quality? 13. Why cannot a throttling calorimeter measure the quality if the steam is very wet? How is the quality measured then? 14. What is the principle of operation of a separating calorimeter? 15. What are Maxwell relations and why are they important in thermodynamics? 16. Show that the internal energy and enthalpy of an ideal gas are functions of temperature only.