Question Paper: Thermodynamics Question Paper - Dec 18 - Mechanical Engineering (Semester 3) - Jawaharlal Nehru Technological University (JNTUH)

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## THERMODYNAMIC- Dec 18

### Mechanical Engineering (Semester 3)

Total marks: 80

Total time: 3 Hours
INSTRUCTIONS

(1) Question 1 is compulsory.

(2) Attempt any **three** from the remaining questions.

(3) Draw neat diagrams wherever necessary.

PART- A (25 MARKS)

**1.a.**What is ideal gas ?

**1.b.**What is the difference between the work transfer and heat transfer?

**1.c.**What is pMN-1. Justify with reason whether it is feasible or not?

**1.d.**A heat pump takes up heat from cold outdoor and transfer it to the warmer Indore space is this evaluation of second law of thermodynamics? Explain.

**1.e.**What is the difference between critical point and triple point?

**1.f.**Is it true that water boils at higher temperature at higher pressure? Explain.

**1.g.**Define the degree of saturation. What are the limiting values?

**1.h.**Distinguish between wet bulb temperature and thermodynamics wet bulb temperature.

**1.i.**Draw the P-V and T-S diagram of lenoir cycle.

**1.j.**Compare otto and Dual cycle for the same maximum pressure and temperature.

PART- B (50 MARKS)

**2.b.**Explain the concept of ideal gas temperature scale.

**2.b.**A milk chilling unit can remove heat from milk at the rate of 4.187 MJ/h. Heat leaking in into milk from surroundings at an average rate of 4.187 MJ/h. Find the time required for Colling a batch off 500 kg of milk from 45°C to 5°C. Take the Cp of milk to be 4.187 MJ/h

OR

**3.a.**Explain what do you understand by concept of Continuum? How will you define density and pressure using this concept?

**3. b.**A balloon is filled with air (200kpa and 300K) such that it become a sphere of diameter 1 m. It is gradually heated in the pressure reasons to 500 kpa. Determine the amount of work done during the process, assuming that the pressure inside the balloon is proportional to the diameter of the balloon.

**4.a.**Is the Third law of thermodynamics, an extension of second law? Is it an independent law of nature? Explain.

**4.b.**Two bodies of equal heat capacities C and temperature T1 and T2 from an adiabatically closed system. What will be the final temperature is one lets this system come to equilobium (i)freely; (ii) reversibly.

OR

**5.a.**Discuss about clausius Inequality.

**5.b.**One kg of ice at -5°C is exposed to the atmosphere which is at 20°C. Ice melt and come into thermal equilibrium with the atmosphere. Determined the entropy increase of the universe.

**6.a.**Stream initially at 0.3 MPa, 250°C is cooled at constant volume. I) At what temperature will stream become superheated vapour. ii) What is a quality of stream of 80°C? iii) What is the heat transferred per kg of stream in cooling from 250°C to 50°C.

**6.b.**Discuss about triple point, critical temperature and critical pressure.

OR

**7.a.**Write the clapeyron equation and and point out its utility.

**7.b.**In a separating and throttling calorimeter the pressure and temperature of steam before throttling is 10bar. The pressure and temperature of stream after throttling is 1.1bar and 110°C respectively. At the separator 0.6 kgs of water is trapped and 3.4 kgs of condensed water is collected from the condenser. Determine the dryness fraction of steam in the main pipeline. Take Cp for superheated steam 2.1kj)kg k.

**8.a.**State Avagadro's Hypothesis.

**8.b.**A gas mixture contain 1 kg of O2 and 3 kg of N2. The pressure and temperature of the mixture are 1 bar and 27°C. Determine: I) Mass fraction amd mole fraction of each constituent ii) Average molecular weight of mixture iii) Partial pressure of constituents iv) Specific gas constant v) Mixture volume vi) Mixture density

OR

**9.a.**A reversible aduabatic process begin at p1 = 10 and T1 =300°C and end with p2=2 bar. Find the specific volume and the work done per kg of fluid (i)if the fluid is air and (ii) The fluid is steam.

**9.b.**Discuss about sensible heating, cooling and dehumidification processes.

**10.a.**Draw the veriation of thermal efficiency again compression ratio of an otto-cycle. TYPE_QUESTION_HERE

**10.b.**An air standard diesel cycle has a compression ratio of 17. The pressure at the beginning of compression stroke is 1bar and temperature is 23°C .The maximum temperature is 1430°C. Determine the thermal efficiency and the mean effective pressure for this cycle. Take X = 1.4.

OR

**11.a.**With a neat sketch explain the working of simple vapourcompression refrigeration cycle and drive the expression of COP.

**11.b.**Define mean effective pressure and thermal efficiency of an air standard cycle.