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Q1. A gas in a cylinder is heated at constant pressure from a temperature of 387°C to 568°C and then cooled at constant volume to 427°C.

The change in specific entropy in the first process is 0.182 kJ/kgK.

After the cool processes the gas expands isentropically to 5 times V1 and a temperature of 17°C.

(a) Sketch PV and Ts diagrams to show the process.

(b) Calculate EACH of the following:

(i) C_v, C_P and y;

(ii) the change in specific entropy in the constant volume process;

(iii) the specific heat in the constant pressure process.

Q2. For air standard Diesel cycle the volume compression ratio is 8/1.

The maximum and minimum temperature are respectively 1500 K and 279 K, and the minimum pressure is 0. 95 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 mean effective pressure. (3)

Note: For air C_v = 0.7181 < kJ/kg K C_p = 1.0051 < 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

Q4. In a steam plant, using reheat, the turbine receives the steam at a pressure and temperature of 20 bar and 300°C respectively. The steam isentropically expands in the first stage until it is just dry saturated. It is then reheated at constant pressure to 250°C and is isentropically expanded in the second stage to a condenser pressure of 1 bar.

The feed pump work can be neglected, there is no undercooling in the condenser.

(a) Sketch the T-s diagram for the cycle.

(b) Calculate the thermal efficiency of the process.

Q5. A vapour compression refr1geratton system using R134a operates between the pressure of 6.6525 bar and 32.433 bar.

It enters the compressor with 10 K of superheating and compressed through a compressor with an isentropic efficiency of 92%.

No undercooling takes place in the condenser.

(a) Draw the cycle on pressure-specific enthalpy and Temperature-specific entropy diagrams.

(b) Calculate EACH of the following:

(i) the temperature leaving the compressor; (ii) the coefficient of performance.

Q6. A fruit juice carrier has 2 spherical tanks each of radius 12 m. They contain liquid at a temperature of 3°C. The tanks are insulated with 600 mm thickness material of fibre glass with a thermal conductivity of 0.04 W /mK.

The outside surface heat transfer coefficient is 2 W /m²K and the outside air temperature is 30°c.

Calculate EACH of the following:

(a) the total rate of heat lost;

(b) the external surface temperature;

(c) the total percentage mass evaporated each 28 days.

Note: Density= 1250 kg/m³ Latent heat of evaporation is 2700 kJ/kg.

Q7. An unknown hydrocarbon fuel combusts with dry air, the resulting products have

the following dry volumetric products, 11% CO₂, 1.5% CO, 2% O₂ and 85.5% N₂.

(a) Calculate the percentage excess air.

(b) Determine the partial pressure of the water vapour and dew point.

(c) Describe the difference between HCV and LCV values.

Note:  [Air contain 21% Oxygen by volume and atmospheric pressure is 1.0135 x 10⁵ Pa]

Q8. A single stage impulse turbine has a mean blade diameter of 1.2 m, and the peed of rotation Is 5093 rev/min. The nozzle angle is 17 degrees to the plane of rotation and the steam leaves the nozzles at 900 mis. The blade velocity coefficient is 0. 91 and there is no axial thrust.

The steam mass flow rate is 0.05 kg/s. Calculate EACH of the following:

(a) the velocity of the blades;

(b) the blade inlet angle;

(c) the blade outlet angle;

(d) the power output.

Q9. A horizontal pipe carrying water tapers from 500 mm diameter to 100 mm diameter. The volumetric flowrate is 0.1 m³/s, before increasing again to a diameter of 330 mm with a difference in height of 7 m.

(a) Calculate the velocities at all points. (6)

(b) Determine the pressure difference between point 1 and 2 and between point 2 and point 3. (10)

Note: the density of water is 1000kg/m³