1. During an 8 hour trial on a boiler the following average data were obtained:

Boiler Pressure = 1400 kPa
Feed Water Evaporated = 28500 kg
Feed Water Inlet = 50 ‘C
Mass of Coal Fired = 4600 kg
Calorific Value = 29100 kJ/kg
Air Supplied per kg of coal = 18 kg
Flue Gas Temperature = 350 ‘C
Boiler Room Temperature = 27 ‘C

Sampled of steam leaving the boiler were passed through a throttling calorimeter and the average value of the pressure and temperature after throttling was 104 kPa and 140 ‘C. Find:

A) the condition of the steam leaving the boiler
B) the boiler efficiency
C) the equivalent evaporation from and at 100 ’C per kg of coal

2. A boiler tube has an outside diameter of 8cm, a wall thickness of 3.5mm and is 6m long. The tube has scale that is 1 mm thick on the inside of the tube. The thermal conductivities of the scale and steel at boiler temperature are 2.32 W/m’C and 46 W/m’C respectively. Calculate the heat transfer and compare it to the heat transfer without scale if the heat transfer through the tube is 39GJ/hr without scale.

3. A) Draw a Pressure-Volume chart with the following lines:
i) Constant Volume expansion from point 1 to point A
ii) Constant Pressure expansion from point 1 to point B
iii) Isothermal expansion from point 1 to point C
iv) Adiabatic expansion from point 1 to point D

B) Air having a pressure of 50kPa abs. and a volume of 1 m3, expands isothermally to a volume of 6 m3. Calculate:
i) External work of the expansion
ii) Heat required to produce the expansion
iii) Pressure at the end of expansion

4. A) Derive the steady-flow formula from the following formula:

Z1 + U1 + P1V1 + v12/2 + Q = Z2 + U2 + P2V2 + v22/2 + W
B) Dry air enters a compressor with a velocity of 6 m/s and an enthalpy of 230 kJ/kg and leaves with a velocity of 12m/s and an enthalpy of 475 kJ/kg. Assuming adiabatic compression and negligible change in potential energy, how much work is required to compress 1 kg of air?

5. A) Draw a pressure-volume chart for a refrigeration cycle and label the 4 processes (6) PG.180
B) Draw a temperature-entropy chart for a refrigeration cycle and label the 4 processes (6) PG.180
C) Identify the 4 processes of a refrigeration cycle (4) PG.181
D) Identify the 4 processes of a refrigeration plant (4) PG. 175

6. A) Draw a basic rankine cycle with no superheater, reheaters or feedwater preheater. (7) PG.12
B) Cannot remember!!!
C) Cannot remember!!!
D) What is the formula for isentropic efficiency.

7. One kilogram of steam at a pressure 4000 kPa and 85 percent dry is expanded under constant temperature until it reaches a pressure of 2000kPa. Find:
A) The heat removed by the expanding steam to it’s surroundings
B) The work done during the process

(Note: Take the internal energy value at Superheat to be 2681 kJ/kg)