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Q1. In a non-flow process 0.4 m³ of a gas is initially compressed from 3 bar and 250℃ to 25 bar and 0.2 m³ according to the law PVⁿ = C. Then the volume of the gas is reduced isothermally to 0.09 m³

Calculate EACH of the following:

a) the temperature after the initial compression (2)

b) the final pressure (2)

c) the specific work done in the initial compression (2)

d) the total specific heat transfer (6)

e) sketch the process on p-V and T-s graphs. (4)

Note: γ = 1.32, n = 3.06, c₀ = .2058 4 J/kgK c_v = 15,59.4 J/kgK

Q2. The ratio of compression of an engine working on the constant volume cycle is 9.3:1. At the beginning of compression the temperature is 32℃ and at the end of heat supply the temperature is 1205℃

Determine EACH of the following:

a) the temperature at the end of compression and expansion (4)

b) the specific net work and thermal efficiency (6)

c) IF V₁ = 0.1 m³ AND P₁ = 1 bar find the volume and pressure at each point in the cycle (6)

Note: For air γ = 1.4, c_v = 0.718 kJ/kgK

Q3. A three -stage reciprocating air compressor onboard a tanker. The compressor is perfectly intercooled and has a clearance ratio of 3.5%. The air properties at induction are 1 bar and 20℃ and the compressor delivers 25m³/min at these conditions

The discharge pressure of the compressor is 15. 50 bar. The stage pressure ratios are equal. And the index of compression and expansion is 1. 34 for all stages.

a) Sketch the p-v diagram of the compression (4)

b) Calculate EACH of the following:

(i) calculate the indicated power of the compression. (8)

(ii) the volumetric efficiency. (4)

Note: For Air c_p = 1005 J/kgK, c_v = 718 J/kgK

Q4. In a steam plant, using reheat, the turbine receives the steam at a pressure and temperature of 20 bar and 400℃ respectively. The steam expands isentropically in the first stage until it is just dry saturated.

It is then reheated at constant pressure to 400℃ and is expanded isentropically in the second stage to a condenser pressure of 0.04 bar.

The feed pump work cannot be neglected, there is no undercooling in the condenser and the steam flow rate is 4. 86 tonne per hour.

Calculate EACH of the following:

a) The power output (14)

b) The specific steam consumption. (2)

Q5. A vapour compression refrigeration cycle uses R124a as a refrigerant. The refrigerant enters the compressor at 1.0637 bar and -15℃, where it undergoes isentropic compression until it reaches 11. 595 bar.

The condenser undercools the refrigerant by 25 K.

a) Sketch the p-h and T-s graphs of the cycle. (4)

b) Determine the following points:

(i) the enthalpy and entropy at the compressor inlet. (2)

(ii) the temperature and enthalpy at the compressor outlet. (4)

(iii) the enthalpy and entropy at the evaporator inlet. (3)

(iv) coefficient of performance COP. (3)

Q7. A gas containing carbon 75%, hydrogen H₂ 24%, and Sulphur 1% by volume is burnt completely with 23% excess air. Air is 21% Oxygen and 79% Nitrogen by volume.

Calculate EACH of the following:

a) The mass of air per 100 m³ of the exhaust gas (5)

b) The volumetric analysis of the exhaust wet gas. (5)

c) The mass analysis of the dry exhaust gas. (6)

Q8. The velocity of steam leaving the nozzles of an impulse turbine is 900 m/s and the nozzle angle is 20°. The blade velocity is 300 m/s and the blade velocity coefficient is 0.7.

a) Sketch the blade velocity diagram for the turbine. (4)

b) For a mass flow of 1 kg/s, and symmetrical blading, calculate EACH of the following:

(i) The blade inlet angle. (4)

(ii) The driving force on the wheel. (5)

(iii) The axial thrust (3)

Q9. A 70 degree bend is fitted in a horizontal section of a 480 mm diameter fresh water cooling system. The cooling system pressure is 2.95 bar, the flowrate is 0.94m³/s and the pressure loss due to the bend is negligible.

Calculate the magnitude of the resultant force acting on the bend. (16)