1. (a) Explain the differences between fire-tube boilers and water-tube boilers with respct to the following:
• construction
• operation
• main mechanisms of heat transfer
• properties and uses of steam produced.
(b) Discuss the major factors which affect the choice of boiler type for particular applications.
(c) A boiler produces superheated steam at 40 bar and 350°C from feedwater at 30°C. The higher heating value (calorific value) of the fuel is 45 MJ kg-1 and the heat from each kg of fuel generates 13.1 kg of steam. Calculate the boiler efficiency based on the higher calorific value of the fuel.
2. (a) Using brief notes explain the function of the following components which make up a steam production and power plant system:
(i) water treatment plant
(ii) de-aerator
(iii) feedwater pumps
(iv) combustion air pre-heater
(v) economiser
(vi) boiler
(vii) steam drum
(viii) superheater
(ix) turbine
(x) condenser
(xi) generator.
(b) Construct a simple block diagram to show these major components of a steam production and power plant system in their correct sequence.
(c) A surface condenser is to be designed to condense 150 000 kg h-1 of dry saturated steam at 0.05 bar. If the overall heat transfer coefficient is 11.5 kW m-2 K-1 and the inlet and outlet water temperatures are 14°C and 24°C respectively, calculate the heat transfer surface area required.
3. (a) Using simple sketches describe the construction and operating principles of the following:
(i) reciprocating compressors
(ii) centrifugal compressors.
(b) Explain the meaning and importance of the phrase 'multi-stage compression with interstage cooling'.
(c) A three-stage compressor takes air at a pressure of 0.96 bar and delivers it at 12 bar. Assuming the intermediate pressures are in geometric progression, find the two intermediate pressures. Take the gas constant R for air as 0.287 kJ kg-1 K-1.
(d) Discuss four examples of the use of compressed air in industry.
4. (a) State the two main groups of compressor in industry and explain the differences between them with respect to method of compression, compression ratio and capacity. Quote an example from each group.
(b) Discuss the factors which affect the choice of a compressor type for particular application.
(c) Select a suitable compressor for each of the following applications; state whether single or multi-stage is indicated. You may use
FIGURE 2 on page 6 of lesson PSR - 3 - 3.
(i) A capacity of 1000 m3 h-1 at a pressure of 9 bar at a steady nonpulsating flowrate.
(ii) A capacity of 10 000 m3 h-1 at a pressure of 100 bar.
(iii) A capacity of 100 m3 h-1 at 100 bar.
Attachment:- Assignment.rar