JNTU
JNTU B.Tech II THERMAL SCIENCE Previous Question Paper (March - 2021 - R16/R13)
Answer any five questions
All questions carry equal marks
Main
Differentiate among open, closed and Isolated systems.
Answer
A closed system (control mass) is one in which only energy (heat and work) can cross the boundary, while the mass remains constant. A control volume or open system allows both mass and energy to cross its boundaries, typically used for analyzing flow devices like turbines and pumps. An isolated system is a special case of a closed system where neither mass nor energy can cross the boundary, meaning the total energy and mass of the system remain constant.
A gas expands according to the equation
Answer
Given the process equation
- Express volume as a function of pressure: V = 1000 / P.
- Differentiate to find dV:dV = -1000 / P2 dP.
- Set up the integral for work: W = ∫ P dV = ∫P1P2 P (-1000 / P2) dP = -1000 ∫P1P2 (1 / P) dP.
- Evaluate the integral: W = -1000 ln(P2 / P1).
- Substitute the values P1 = 1000 kPaandP2 = 500 kPa:W = -1000 ln(500 / 1000) = -1000 ln(0.5).
- Calculate the result: W = -1000 × (-0.693) = 693 kJ/kg.
The work done by the gas is 693 kJ/kg.
State and explain the Zeroth law of Thermodynamics.
Answer
Sign in to view the complete answer paper.
Derive the steady flow energy equation and reduce it for a turbine, pump, nozzle and a heat exchanger.
Answer
Sign in to view the complete answer paper.
Derive the expression for reversible work done by a closed system if it interacts only with the surroundings.
Answer
Sign in to view the complete answer paper.
Air in a closed vessel of fixed volume 0.15 m3 exerts pressure of 12 bar at 250°C. If the vessel is cooled so that the pressure falls to 3.5 bar, determine the final pressure, heat transfer and change of entropy.
Answer
Sign in to view the complete answer paper.
An engine working on dual cycle has bore of 20 cm and stroke of 40 cm. Compression ratio is 14.5 and pressure ratio at constant volume heat addition process is 1.5. The constant volume heat addition cut-off takes place at 4.9 % of the stroke. Assuming
Answer
Sign in to view the complete answer paper.
Show that the efficiency of the Otto cycle depends only on the compression ratio.
Answer
Sign in to view the complete answer paper.
What is a Perpetual Motion Machine of the first kind? Why is it impossible?
Answer
Sign in to view the complete answer paper.
A trial carried out in a four stroke single cylinder gas engine gave the following results. Cylinder dia = 300 mm, Engine stroke = 500 mm, Clearance volume = 6750 cc, Explosions per minute = 100, Pmax = 765 KN/m2 Net work load on the brake = 190kg, Brake dia = 1.5 m, Rope dia = 25mm, Speed of the engine = 240 rpm, Gas used = 30 m3/kghr, Calorific value of gas = 20515 kJ/m3. Determine the compression ratio, mechanical efficiency, and indicated thermal efficiency. Assume
Answer
Sign in to view the complete answer paper.
Describe the working principle of simple carburetor along with a suitable diagram.
Answer
Sign in to view the complete answer paper.
Explain with suitable sketches, explain the working of two stroke engine.
Answer
Sign in to view the complete answer paper.
Show that the efficiency of a reversible engine operating between two given constant temperatures is the maximum.
Answer
Sign in to view the complete answer paper.
Draw and explain the valve timing diagram for four stroke engine.
Answer
Sign in to view the complete answer paper.
Write short notes on:
Constant volume gas thermometer
Answer
Sign in to view the complete answer paper.
Modes of fuel admission to I C engine cylinder
Answer
Sign in to view the complete answer paper.
Equivalence of Kelvin-Planck and Clausius Statements.
Answer
Sign in to view the complete answer paper.