JNTU
JNTU B.Tech III THERMODYNAMICS FOR PETROLEUM ENGINEERS Previous Question Paper (February - 2022 - R18)
Answer any five questions. All questions carry equal marks.
Main
Three moles of nitrogen at 300C contained in a rigid vessel, its heated to 2500C. How much heat is required to do this, it vessel weight 100 kg and has a capacity of 0.5 kg/kgC, how much heat is required? For nitrogen Cv = 20.8 J/molC, Cp = 29.1 J/molC.
Answer
To calculate the total heat required, we must consider the heat absorbed by both the nitrogen gas and the rigid vessel. The temperature change is ΔT = 250°C - 30°C = 220°C.
1. Heat required for nitrogen (Q_gas): Using the formula Q = n * Cv * ΔT, where n = 3 moles, Cv = 20.8 J/mol°C, and ΔT = 220°C:
2. Heat required for the vessel (Q_vessel): Using the formula Q = m * C_vessel * ΔT, where m = 100 kg, C_vessel = 0.5 kJ/kg°C (or 500 J/kg°C), and ΔT = 220°C:
3. Total heat required (Q_total):
Differentiate between reversible and irreversible processes.
Answer
A reversible process is an idealized process that occurs infinitely slowly, such that the system remains in thermodynamic equilibrium at every stage. It can be reversed without leaving any trace on the surroundings, and it produces the maximum possible work.
An irreversible process occurs at a finite rate and involves internal dissipative effects such as friction, turbulence, or unrestrained expansion. It cannot be reversed to restore the system and surroundings to their initial states without external work, and it results in an increase in the total entropy of the universe.
For an adiabatic process prove that:
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Calculate ΔU and ΔH in kJ for 1kmol water as it is vaporized at temperature of 373K and constant pressure of 101.3kPa. The specific volume of liquid and vapor at these conditions are 1.04 × 10-3 and 1.675 m3/kmol respectively. 1030 kJ of heat is added to water for this change.
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Explain P-T diagram for a pure substance.
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Calculate the enthalpy and entropy departure for n-octane vapor at 427.85 K and 0.215 Mpa, using the generalized Redlich-Kwong equation of state a=4.426 m6 Pa Mol2 and b=164.3 × 10-6 m3/mol; Z=0.9308, B=9.9306 × 10-3.
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Find the compressibility factor at the critical point for a gas obeying Vander Waal equation of state.
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Derive the Vander Waals constants in terms of critical properties Tc and Pc.
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A small metallic object 4 kg in mass at a temperature of 500 K is thrown into the lake which is at 300 K. Calculate the change in entropy of the universe. Data: CP of object=0.50 kJ/(kg.K)
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An adiabatic nozzle receives dry saturated steam at 0.6 MPa (6 bar) with negligible velocity. The steam leaves the nozzle as dry saturated steam at 0.15 MPa (1.5 bar). Calculate the exit velocity of the steam. Data: Saturated steam at 6 bar: Hv=2756.80 kJ/kg, Saturated steam at 1.5 bar: Hv=2693.60 kJ/kg.
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Derive Maxwell’s equations from first principles.
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Derive the expression for activity coefficient if solution follows the Margules equation as a model of solution behavior.
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The partial molar volume of methanol in a methanol-water solution at X1=0.3881 is 39.176 × 10-6 m3/mol. The density of the mixture is 905 kg/m3. Calculate the partial molar volume of water in the solution.
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For the VLE system ethyl ethanoate(1)/n-heptane(2), assuming the validity of modified Raoult’s Law make BUBL P calculations at T=343.15 K, x1 = 0.05. Data: P1sat = 79.80 kPa and P2sat = 40.50 kPa; ln γ1 = 0.95 x22; ln γ2 = 0.95 x12.
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Explain the solid-liquid equilibrium (SLE) with neat diagram.
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