UPTU Previous Year Question Papers
VI Semester TCH Examination 2006-07
Chemical Engineering Thermodynamics -1
Note: Attempt all questions.
Steam table and other thermodynamic
charts are permitted. Missing data may be suitably assumed.Be precise in your answer.
1. Attempt any four parts of the following :
(a) A hydroturbine operates with a head of 50 m of water. Inlet and Outlet conduits are 2 meters in diameter. Estimate the mechanical power developed by the turbine for an outlet velocity of 5ms-1.
(b) A 0.4m3 rigid vessel initially contains saturated liquid-vapour mixture of water at 100°C. The water is now heated unti it reaches the critical state. Determine the mass of the liquid water at the initial state.
(c) Steam flows at steady state through a nozzle, 25 cm long and with an intel diameter of 5 cm. At the nozzle entrance the temperature and pressure are 320°C and 700 kPa, and the velocity is 30 m/s.At the nozzle exit, the steam temperature and pressure are 240°C and 350 kPa Property values are : H^= 3112.5 kJ kg !(entrance) H2 = 2945.7 kJ kg-1 Vx = 388.61 cm3 g~x V2 = 667.75 cm3 g~x
2. What is the velocity of the steam at the nozzle exit ?
(d) An insulated evacuated tank of 1.75 m3 volume is attached to a line containing steam at 400 kPa and 250°C. Steam flows into the tank until the pressure in the tank reaches 400 kPa. What is the final temperature in the tank ?
(e) A spherical balloon contains 5 kg of air at 200 kPa and 500 k. The balloon material is such that the pressure inside is always proportional to the squam of the diameter. Determine the work done when the volume of the balloon doubles as a result of heat transfer.
(f) A rigid tank contains water vapour at 200°C and an unknown pressure. When the tank is cooled to 150°C, the vapour starts conducting. Estimate the initial pressure in the tank.
2. Attempt any two parts of the following :
(a) Determine the molar volume of n-butane at 2+4+4=10 510 K and 25 bar by
(i) The ideal gas equation
(ii) The generalized compressibility factor correlation
(iii) The generalized virial coefficient concetation Given data :
Z° = 0.865, Z’ = 0.038, W = 0.200 B° = -0.232, B’ = 0.059 Z=l + BPc KRTC J Pr Tc = 425.1 K, Pc = 37.96 bar
(b) One mole of an ideal gas, initially at 30°C and 1 bar, undergoes the following mechanically reversible changes. It is compressed isothermally to a point such that when it is heated at constant volume to 120°C its final pressure is 12 bar. Calculate Q, W, AU and AH for the process.Take Cp = R and Cv =R
(c) Write notes on the following :
(1) Acentric factor
(2) P-V diagram of a pure substance showing all three phases
(3) Generalized compressibility chart.
3. Attempt any four parts of the following :
(a) Derive Carnot’s equation for an ideal gas.
(b) An ideal gas is Throttled from 10 atmorphence pressure to 2 atm If the initial temperature in 30°C, what is the change in entropy ?
(c) An inventor claims to have devised a cyclic engine which exchange heat with reservoirs at 25°C and 250°C, and which produces 0.45 kJ of work for each kJ of heat extracted from the hot reservoir. Is the claim believable ?
(d) A heat engine which rejects waste heat to a sink at 310 K has a thermal efficiency of 36 percent and a second law efficiency of 60 percent. Determine the temperature of the source that supplies heat to this heat engine.
(e) What is the ideal work for the separation of an equimolar mixture of methane and ethane at 175°C and 3 bar in a steady-flow process into product streams of the pure gases at 35°C and 1 bar if sumudays=™K ?
(f) For an ideal gas prove that
4. Attempt any two of the following :
(a) Derive the following relations :
(b) An insulated, vertical piston-cylinder device 10 initially contains 5 kg of water, 4 kg of which is in the vapour phase. The mass of the piston is such that it maintains a constant pressure of 300 kPa inside the cylinder. Now steam at 1 MPa and 400°C is allowed to enter the cylinder from a supply line until all the liquid in the cylinder has vaporized. Determine the final temperature in the cylinder and the mass of the steam that has entered.
(c) Nitrogen gas is compressed for 100 kPa and 5+5=10 27°C to 600 kPa by a 5-kW compressor. Determine the mass flow rate of nitrogen through the compressor, assuming the compression process to be (i) polytropic with n = 1.3 and (ii) ideal two stage polytropic with n = 1.3 show the process on P-V diagram.
5. Attempt any two of the following :
(a) A refrigerator use R-134 a as the working fluid and operates on an ideal vapour-compression refrigeration cycle between 0.12 and 0.7 MPa. The mass flow rate of the refrigerant is 0.05 kg/s. Show the cycle on a T-S diagram with respect to saturation lines. Determine :
(1) The rate of heat removal from the refrigerated space and the power input the compressor
(2) The rate of heat rejection to the environment
(3) The C O P. Data : R 134 a (saturated)
(b) An absorption refrigeration system is to 10 remove heat from the refrigerated sapce at – 10°C at a rate of 15 kW, while operating in an environment at 25°C. Heat is to be supplied from a solar pond 85°C. What is the minimum rate of heat supply required ?
(c) Write notes on the following :
(1) Jet engines
(2) Linde lqiue faction process
(3) Bryton cycle
(4) Cogeneration system for chemical process plants.