IFS - Indian Forest Service Chemical Engineering Previous Year Paper (2004)
PAPER - I : SECTION A
1. Answer any four of the following (10 x 4 = 40)
(a) (i) What is time dependent flow ? With the help of this phenomenon, explain the meaning of Thixotropic liquid and Rheopeptic substances.
(ii) Write the power law equation for dilatant and pseudo plastic fluids, and explain the terms ‘flow consistency index’ and ‘flow behaviour index’.
(b) Derive an equation for steady conduction in the radial direction of a hollow cylinder. From the equation, explain the term log-mean radius. Under what condition, can the log-mean radius be replaced by arithmetic mean radius?
(c) In a double pipe heat exchanger, a hot fluid is cooled from 150 to 100°C by using cold water, which is heated from 30 to 50°C. Derive a suitable expression to prove that there is a distinct advantage of using the exchanger in counter-current flow over that of using it in parallel flow.
(d) Explain how thermal condition of feed influences the liquid or vapour flow rate around the feed plate of a rectification column. What common factor can be used for characterizing five different feed conditions? From the value of this common factor, explain the meaning of horizontal and vertical feed lines.
(e) Explain the phenomenon of primary nucleation in the process of crystallization, and illustrate the difference between homogeneous and heterogeneous nucleation.
2. (a) For an incompressible fluid, write the Bernoulli equation for fractionizes flow. What correction would you apply for incorporating fluid friction? Explain the difference between skin friction and form friction. (10)
(b) What is terminal velocity? Write the equation for terminal velocity for the flow of a single particle through a fluid under the action of (i) gravity and (ii) centrifugal force. How is the equation for terminal velocity under free settling condition modified for hindered settling conditions? (10)
(c) What is a ball mill? Derive an equation for the critical speed of a ball mill. (10)
(d) What is a venture meter? Describe the principle of working of a venture meter and write an expression for the venture coefficient. (10)
3. (a) An air water system has a dry bulb temperature of 65.5°C and a wet bulb temperature of 54.5°C.
(i) If the air is cooled to 37.8°C, what per cent of the moisture will condense?
(ii) If the air is again heated to 65.5°C, how much heat will be required per kg of dry air? Specific heat of air = 0.23 kcal/ (kg 0C). (10)
(b) A spherical particle of ethanol of 10 mm diameter is evaporating in an air stream at 26°C. The thickness of the stagnant air surrounding the particle is 1.5 mm. Vapour pressure of ethanol at 26°C is 60 mm Hg and the mole fraction of ethanol in the main stream of the air is 0.005. The diffusion coefficient of ethanol in air is 1.04 × 10-5 m2/sec and the value of R is 82.06 × 10-3 m3 atm/kg mole. Determine,
(i) The mole fraction of ethanol at different positions across the stagnant layer.
(ii) Rate of evaporation of the particle per second. (10)
(c) What are different types of packing that are used in an absorption tower? Explain a simple procedure for calculating the height of a packed tower for absorption of a single component from a gas mixture. (10)
(d) What is critical moisture content? Describe the method for drying of a wet solid before it reaches the critical moisture content. (10)
4. (a) Develop a relation between heat transfer and fluid friction by using the Reynolds’s Analogy. (10)
(b) (i) What is a radiation shield? How does it help in reducing radiant heat loss?
(ii) A double walled spherical container is used for storing liquid oxygen. The diameter of the inner and outer walls of the container is 30 cm and 36 cm, respectively. The surfaces of both the spheres are plated, so that their emissivity is 0.05. Determine the rate at which oxygen will evaporate at -183°C, when the outer wall of the sphere ismaintained at 20°C. Latent heat of evaporation of oxygen is 57.2 kcal/kg. (5 + 5)
(c) What are drop wise and film wise condensation? Mention the conditions that favour drop wise condensation. Describe how the heat transfer coefficient in a vertical condenser is influenced by the height of the condenser. (10)
(d) What is effectiveness of a heat exchanger? Derive a relation between the effectiveness and number of transfer units for a countercurrent heat exchanger. (10)
5. Answer any four of the following (10 × 4 = 40)
(a) What are the relative advantages and disadvantages of the proportional, integral and derivative control actions? What are their characteristic effects on the closed loop response for a process?
(b) Explain briefly the essential elements of a computer controlled process system.
(c) What is reverse osmosis? How can it be used for the separation of a solute from an aqueous solution?
(d) What is molecular distillation? With a neat sketch describe the working of a molecular distillation unit.
(e) Discuss how wind load is taken care of in the design of a tall vertical vessel.
6. (a) Illustrate the principle of separation of gases by using non-porous membrane. (10)
(b) Discuss about electrolytic regeneration of mixed bed ion exchange resins. (10)
(c) Explain the process of diffusion dialysis and mention its applications. (10)
(d) What are absorption and extraction type separation processes? Illustrate them with examples. (10)
7. (a) Discuss how to find the frequency response of a proportional + integral controller, (10)
(b) Explain how a strain gauge is used for pressure measurement. (10)
(c) Illustrate the process of feed forward control. (10)
(d) Write a relationship that will give the molar or specific enthalpy of a multi-component liquid at temperature T, with known composition for N components. What are the principal control considerations that affect the scope of mathematical modeling of a chemical process? (10)
8. (a) Illustrate the method for the design of a conical head of a cylindrical pressure vessel. (10)
(b) Discuss about major loads and subsidiary loads that must be considered for the design of a pressure vessel. (10)
(c) What are skirt supports? Discuss the method for calculating the thickness of a skirt support. (10)
(d) Discuss the method for calculating the thickness of the shell of a thin wall pressure vessel. (10)
PAPER - II : SECTION A
1. Answer any four of the following
(a) Explain the graphical procedure for finding the concentrations in a series of mixed reactor. (10)
(b) A solution of FeCl3 in water contains 64.1% FeC13 by weight. Calculate the yield of FeC13.6H2O crystals obtained from 1000 kgs solution, if cooled to 27°C. Solubility at 27°C = 68.3% by weight. (10)
(c) Derive the following relation from the fundamentals. (10)
(d) Explain the procedure to calculate the bubble pressure 8 dew pressure for a given ideal Binary mixture. (10)
(e) Derive the performance equation for a given 1st order Ideal CSTR operating at steady-state conditions. (10)
2. A Producer gas with composition by volume 27.3% CO, 5.4% CO2, 0.6% O2, 66.7% N2 is burnt with 20% excess air. If the combustion is 98% complete, calculate the composition, by volume, of the flue gas. (40)
3. Substance A in a liquid reacts to produce R & S as follows:
A feed (CA0 = 1, CR0 CS0 = 0) enters two mixed reactors in series (τ1 = 2.5 min, τ2 = 5 min). Knowing the composition in the final reactor ( ) 1 1 1 CA = 0.4, CR = 0.4, CS = 0.2 , find the compositions leaving the 2nd reactor. (40)
4. The system (1) n-pentane (2) n-hexane (3) n-heptane obeys Raoults law, for a system at 105°C. In a flash drum has overall composition of Z1 = 0.25, and Z2 = 0.45. Determine,
(a) Bubble pressure, Dew pressure and its composition.
(b) L (Liquid rate), V (Vapour rate) and xiyi when The data of Antoine’s constants are: (40)
5. Answer any four of the following
(a) What are the various steps involved for calculating Total Product Cost? (10)
(b) What is profitability? Discuss different methods for evaluating the profitability. (10)
(c) Briefly explain the concept of straight and mixed fertilizers. List out various sources for the manufacture of Ammnonium sulphate. (10)
(d) Describe in detail the activated sludge process. (10)
(e) What is polymerization? Explain different methods of polymerization. (10)
6. The total capital investment for a chemical plant is Rs. 15, 00,000 and the plant produces 30 laths kg of product annually. The selling price of the product is Re. 0.41/kg. Working capital amounts to 15% of total capital investment. Raw material costs for the products are Re. 0.045/kg, labour cost Re. 0.04/kg. Distribution costs are 5% of the total product cost.
(a) Manufacturing cost/kg of product
(b) Total product cost/year
(c) Profit/kg of product before taxes. (40)
7. (a) Describe with neat flow sheet the manufacture of soap by continuous process. (20)
(b) With a neat flow sheet explain the manufacture of LDFE. (20)
8. (a) Explain the thermal processes for the treatment of solid wastes. (20)
(b) Discuss the various sources of air pollutants and their effect on man and his environment. (20)