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Q1) 0.08 kg of Helium is compressed isentropically from 0.325m³, 1.5 bar and 20℃ to 4.8 bar.

It is then heated at constant volume to 680 K.

(a) Sketch PV and Ts diagrams. (2)

(b) Calculate EACH of the followings.

(i) The Volume and Temperature at the end of the initial compression; (5)

(ii) The net heat; (3)

(iii) The net work; (3)

(iv) The total change in entropy. (3)

Note: C_p = 5234 J/kgK  and C_v = 3153 J/kgK

Q2. The ratio of compression for an engine working on the otto cycle is 7: 1.

At the beginning of compression, the. temperature is 2°C with a pressure of 0.89 bar. The maximum cycle pressure is 18 bar.

(a) Sketch a pV and Ts graph of the cycle.

(b} Calculate EACH of the following:

(i} the temperature at all points

(ii) the air standard efficiency of the cycle

(iii} the thermal efficiency for the ideal Carnot cycle.

Note: For air C_v = O. 718 kJ/ kgK and C_p = 1.005 kJ/kgK

Q3. A single-acting, TWO stage reciprocating air compressor fs designed for minimum work with perfect intercooling, and the LP cylinder has a volumetric efficiency of 94%. The compressor delivers 5.8 kg/min of air from an initial cond1t1on of 1.013S bar and 18°C.

In each stage the clearance volume is 4% of the respective swept volume, and the index for all compressions and expansions is n = 1. 37.

The speed of rotation is 420 r/min.

(a) Sketch the cycle on a pressure-volume diagram.

{b) Determine EACH of the following:

(i) the delivery pressure;

(ii) the power;

(iii} the volume per cycle for the LP stage.

Note: For air C_v = 0.718kJ/kgK C_p = 1. 005kJ I kgK

Q5) A vapour compression refrigeration system operates between the pressures of 4.233 bar and 9.607 bar.

R12 refrigerant enters the compressor dry saturated and is isentropically compressed. Upon leaving the condenser it is undercooled by 10 K. The mass flow rate is 1867  kg/hour.

(a) Sketch the cycle on pressure – specific enthalpy and temperature – specific entropy diagrams. (2)

(b) Calculate EACH of the following:

(i) the dryness fraction of the refrigerant entering the evaporator; (3)

(ii) the temperature leaving the compressor; (5)

(iii) the compressor power; (4)

(iv) the coefficient of performance. (2)

Q7. A Natural gas consists of the following volumetric composition, Propane

(C₃H₈) (2. 7%). Methane (CH₄) (88.6%), Ethene (C₂H₄) (3.5%) and Sulphur (S₂) (5.2%) .

Determine the Stoichiometric volume analysis of air, for the complete combustion of 1m³

Q8. A single stage impulse turbine has a mean blade diameter of 580 mm, and the speed of rotation is 10560 rev/min. The nozzle angle is 18 degrees to the plane of rotation and the steam leaves the nozzles at 829 m/s. The blade velocity coefficient is 0.9 and there is no axial thrust.

For a steam mass flow rate of 0.15 kg/s, determine EACH of the following:

(a) the velocity of the blades; (2)

(b) the blade inlet angle; (6)

(c) the blade outlet angle: (4)

(d) the power output. (4)

Q9) A centrifugal pump impeller is 665 mm outside diameter and 300 mm inside diameter and runs at 360 rpm. The radial velocity at the inlet and outlet is 7.2  m/s.

The velocity of the whirt at the exit is 6.1  m/s, and the volumetric flow rate throughout is 0.1355  m³/s.

Calculate EACH of the following:

(a) the blade outlet angle; (4)

(b) the blade inlet angle; (4)

(c) the width of the impeller at the inlet and outlet; (4)

(d) the power. (4)

Note: The working fluid is water.