FACULTY OF PRACTICAL SCIENCE. METALLURGY III. (Students in Electro-metallurgy answer questions 3, 4 and 5). 1. Discuss the ordinary method of extracting zinc from its ores as practiced in America, and show how the operation is affected by iron, lead, sulphur and silica. 2. Describe the process at present in operation for recovering nickel from the pynhotite ores of the Sudbury district. 3. Given the heat formation of Al2O=392 large calories, one joule=.00024 large calories, and that 96,540 coulombs of electricity will liberate one chemical equivalent weight in grammes. Determine the critical voltage necessary to decompose the oxide and the cost of power for producing one pound of aluminium; when the amparage efficiency is 60%, the voltage efficiency 60%, and the electric power can be obtained at $15.00 per H.P. year. 4. Mention three metallurgical processes that require the high temperature that can be obtained by the electric arc or resistance furnace, and describe any one of them. 5. Describe in a few words the operation, principle. and practical uses of the Heroult pig iron furnace, Heroult steel furnace and Kjellin furnace. FACULTY OF PRACTICAL SCIENCE. THERMODYNAMICS II. 1. Discuss the difference between the function of an engine flywheel and that of a governor. Explain the action of an automatic cut-off governor and of a throttling governor. What are the advantages and disadvantages of each of these types? 2. Show how to determine the quality of steam with the help only of a steam gauge, a thermometer, a tank and a pair of scales. Explain the theory and the construction of a throttling calorimeter. If the steam pressure in the main be 80 lbs. and the temperature in the calorimeter 220° F., the pressure in the calorimeter being atmospheric, calculate the quality of the steam in the main. 3. A steam engine direct-connected to a D. C. generator and running non-condensing, gives the following results in an efficiency test: Dia. of cylinder=16", stroke 20′′. Mean effective pressure=36.5 lbs. per sq. in. Speed= 181 r.p.m. Steam used per hour 4200 lbs. Quality of steam 99%. Steam pressure=80 lbs. gauge. "Load 110 volts, 780 amperes. (a) The electrical horse-power. (d) Lbs. of steam per I. H. P.-hour. (e) Lbs. of steam per E. H. P.-hour. (f). Thermal efficiency of engine based on I. II. P. assuming an evaporation of 9 lbs. of steam per lb of coal and $3.00 for the price of a ton of coal. (h) The over-all efficiency from switch-board to coal pile, assuming 13,000 B.T.U. per lb. of coal (i) The probable steam consumption of the engine, if the steam were superheated 100°F. (Specific heat of superheated steam .55). 4. A boiler evaporated in a 12 hour test 28,300 lbs. of water, consuming 3,570 lbs. of coal. Steam pressure 80 lbs. gauge. Quality of steam=98%. Calculate: (a) the equivalent evaporation from and at 212° per lb. of dry coal; (b) the boiler horse-power developed ; (c) the thermal efficiency. The calorific value of the coal as fired was 13,000 B.T.U. and it contained 7% moisture. 5. Describe fully the arrangement of an ordinary jetcondensing plant. Explain why in some installations a surface condenser is preferred, and in others a jet condenser. 6. Show how the various quantities of the steam tables are represented by areas on the Entropy-Temperature Diagram, how to obtain the heating curve of water and the saturation-curve of steam, and how to calculate the ideal efficiency of a steam engine by means of this diagram. Latent heat of steam at atm. pressure = 965.7. FACULTY OF PRACTICAL SCIENCE. THERMODYNAMICS III. A gas engine is working on the ordinary Otto cycle. The fuel is producer gas of 135 B.T.U. per cu. ft, lower heat value, and the mixture is in the ratio of 1:1. Initial temperature of charge = 75°F. Compression: 160 lbs. absolute. Calculate (a) The ideal pressure, volume and temperature at the beginning and end of each phase. (b) The ideal mean effective pressure. (c) The ideal efficiency of the cycle. 2. A certain gas engine develops in a test 100 B.H.P., with the same gas as in question No. 1, and the thermal efficiency based on B.H.P. is 24%. If the temperature in the exhaust pipe close to the engine be 860° ̊F., calculate approximately how much steam at 5 lbs. gauge pressure could be raised for heating purposes by utilizing the heat of the exhaust, and using the jacket water which leaves the cylinder at 140°F., as feed water. Assuming that 50% of the heat energy supplied is lost in the jacket water, what percentage of the water would be vaporized? Also calculate the heating surface required in the boiler. 3. Discuss the value of the Entropy-Temperature Diagram for the analysis of an engine test and explain how to construct it from a given indicator card and the results of a test. Assume proper numerical data. 4. Calculate by the use of the E. T. diagram the ideal thermal efficiency of a steam engine working on the Rankine cycle. Boiler pressure 150 lbs. gauge, 150°F. superheat, 28" vacuum, Barometric pressure 29.6 inches of Mercury. Calculate also the theoretical steam consumption. |