Assignment 1 Thermodynamics

ASSIGNMENT 1 ELEMENTS OF MECHANICAL ENGINEERING 1. Explain the terms: State, process, path, cycle, Thermodynamic equilibrium, property, open system, closed system, adiabatic system and isolated system 2. What do you mean by quasi static process? List its characteristics. 3. A vessel of cylindrical shape, 50 cm diameter and 75 cm height, contains 4 kg of a gas. The pressure gauge mounted on the vessel indicates 620 mm of mercury above atmosphere. If the barometer reading is 760 mm of mercury, calculate the absolute pressure of gas in bar. Also determine the density and specific volume of the gas. (Ans. 1.841 bar, 27.21 kg/m3, 0.03675 m3/kg ) 4. In a piston cylinder arrangement, the non flow process is given by v=200/p m³, where p is in bar. Find the work done when the pressure increases from 1 bar to 10 bar. Also indicate whether the process is compression or expansion. (Ans. -460.4 J, Compression) 5. A non flow reversible process occurs for which p=3v²+1/v where p is in bar and v in m³. What will be the work done when v changes from 0.5 to 1.5 m³. (Ans. 4.349 x 105 J) 6. An ideal gas requires 1150kJ/kg of heat to raise its temperature from 20ºC to 100ºC, when heated at constant pressure. When heat is supplied to the same gas at constant volume, the heat requirement is 825 kJ/kg for the same temperature range. Determine specific heat at constant pressure, specific heat at constant volume and adiabatic exponent. (Ans. 14.375 KJ/Kg k, 10.312 KJ/Kg k, 1.394) 7. An air bottle of 20 liters capacity used for starting a diesel engine contains air at 0.11 MPa and 20ºC. After charging the bottle, the pressure reaches 1.5 MPa and temperature rises to 50ºC. Make calculations for mass of air added to the bottle. (Ans. 0.297 Kg) 8. A cylinder contains 1kg of a certain fluid at an initial pressure of 20 bar. The fluid is allowed to expand reversibly behind a piston according to a law pv²=constant until the volume is doubled. The fluid is then cooled reversibly at constant pressure until the piston regains its original position. Heat is then supplied reversibly with piston firmly locked in position until pressure rises to original value of 20 bar. Calculate the net work done by the fluid for an initial volume of 0.05m³. (Ans. 25 KJ) 9. A tank of 0.35 m³ capacity contains H2S (molecular mass 34) at 300K. When 2.5 kg of air is withdrawn, the temperature of the tank becomes 288K and pressure 10.5 bar absolute. Calculate the mass of gas initially present in the tank. Also determine the initial pressure. (Ans. 7.7 Kg, 16.1 bar) 10. Define and explain the Zeroth law of thermodynamics.