Thermal Science

(b) An engine working on the Otto cycle is supplied with air at 0.1 MPa,35 °C. The compression ratio is 8. Heat supplied is kJ/kg. Calculate the maximum pressure and temperature of the cycle, the cycle efficiency and the mean effective pressure. For air C_p=1.005 kJ/kgK and C_v -0.718 kJ/kgK. 

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(j) Explain turbo-jet engine with a neat diagram.

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(i) Which of the following cycles is more efficient for the conditions of same maximum pressure and temperature: Otto cycle, Diesel cycle, Dual cycle. Explain with the help of p-v and T-s diagrams.

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(h) Sketch the p-v, T-s and h-s diagrams of the reversible cycle that represents a simple steam power plant.

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(g) What is limitation of using Throttling calorimeter to measure the dryness fraction of a very wet steam? Justify with the help of h-s diagram

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 (f) Can two reversible adiabatic paths intersect each other? Justify.

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 (e) State and explain the Gouy-Stodola theorm.

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 (d) How do you differentiate heat pump from a refrigerator? Can you use same plant as heat pump in winter and refrigerator in summer?

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(c) State Carnot's theorem? Also state the corollary of Carnot's theorem.Which law of thermodynamics do these statements represent?

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(b) What is flow work? How is it different from displacement work?

In a gas turbine plant working on the Brayton cycle with a regenerator of 70% effectiveness, the air at the inlet to the compressor is at 0.1 MPa, 27 °C, the pressure ratio is 6, and the maximum cycle temperature is 900°C. If the turbine and the compressor each has efficiency of 85%, find the percentage increase in efficiency due to regeneration 

(a) A person starts a 50 W Table fan in an insulated room of volume 90m. He expects to cool the room from 35 °C (pressure= 101 kPa) and aloows the fan to run for 4 hours. Will the fan heat or cool the room? What will be the final temperature of the room after 4 hours? C_v=0.718 kJ/kgK, R-0.287 kJ.kgK

(a) What is cut-off ratio? How does it affect the air standard efficiency of the diesel cycle?

In a thermal power plant operating on a rankine cycle, superheated steam produced at 5 MPa and 500°C is fed to a turbine where it expands to a condenser pressure of 10 kPa. If the net power output of the plant is to be 20 MW, Determine:

(a) Heat added in the boiler per kg of water

(b) thermal efficiency of the cycle

(c) mass flow rate of steam in kg/s

(d) mass flow rate of cooling water in condenser if the cooling water enters the condenser at 25°C and leaves at 35°C.

(b) During a certain process, a vapour condenses at 700K and transfer· heat to water evaporating at 500 K. The steam thus produced is used in power cycle which rejects heat to surroundings at 300K, Calculate the fraction of energy that becomes unavailable due to irreversible heat transfer. 

(a) Explain (1) Gibbs function (ii) Dead state (iii) Second law efficiency

(b) A rigid closed tanl of volume 3m³ contains 5 kg of wet steam at pressure of 200 kPa. The tank is heated until the steam becomes dry and saturated. Determine the final pressure and heat transferred to the tank 

(a) Derive the Maxwell's equations. 

(b) A reversible engine exchanges heat with 3 sources at 200 K, 300 K and 400 K respectively. If it draws 5 MJ of heat from source at 400 K and does 840 kJ of work. Find the values of heat it exchanges with the sources at 200 K and 300 K. 

(a) Using entropy principle, Calculate the maximum amount of work that is obtainable from a finite body and a thermal energy reservoir. 

(b) Two reversible heat engines HEI and HE2 are working in series, HEI rejecting heat to HE2. Engine HEl receives 250 kJ heat at a temperature of 410 °C from a hot source, while engine HE2 rejects heat to sink at 5 °C. If the work output of HE1 is twice as that of HE2, Find (a) Intermediatte temperature between HEI and HE2, (b) efficiency of each engine and heat rejected to the cold sink.