Kerala PSC Range Forest Officer – Kerala Forest and Wildlife Department Previous Question Paper – 019/2026

The Commission publishes this paper without an answer key, so no answers are shown.

1. Define recycle, bypass and purge. How does recycle affect reactor size? (5)

2. A liquid-phase reactor carries out the reaction : A → B. Fresh feed to the reactor is 100 kmol/hr of pure A. The single-pass conversion of A is 30%. Calculate : Amount of A leaving the reactor, B formed and the total outlet flow rate. (5)

3. What are the limiting conditions to be followed by any equation of states? (5)

4. Define partial molar property. Explain its physical significance. (5)

5. Write about the rheological behaviour of any 5 non-Newtonian fluids and give examples for each. (5)

6. Explain the extended Bernoulli’s equation including :
• Pump work
• Head loss (5)

7. Write about any two methods used for the particle size distribution of subsieve particles? (5)

8. Distinguish between free and hindered settling. (5)

9. Prove that the rate of heat transfer between two infinite parallel plates reduces to half its value when a very thin radiation shield is placed between them. State the assumptions required, if any. (5)

10. A brick wall of area 25 m² and thickness 25 cm has a refractory lining 5 cm thick. Surface temperatures are 700°C and 100°C. Calculate heat lost per day and the interface temperature. Thermal conductivities are 0.5 W/(m·K) for brick and 2 W/(m·K) for refractory. (5)

11. Explain why the Log Mean Temperature Difference (LMTD) is used instead of the arithmetic mean temperature difference in the analysis of heat exchangers. State the conditions under which the LMTD method is applicable and mention one limitation of the method. (5)

12. Explain the physical significance of the thermal boundary layer in forced convection over a flat plate. Discuss how the Prandtl number influences the relative thickness of the thermal and hydrodynamic boundary layers and the heat transfer coefficient. (5)

13. Analyse why the penetration theory predicts higher mass-transfer coefficients than the film theory, with the help of physical reasoning. (5)

14. Justify the effect of reflux ratio on the number of theoretical stages, energy requirement, and product purity in a distillation column. (5)

15. Differentiate between gas-phase and liquid-phase controlled mass transfer with suitable equations. (5)

16. Write down five differences between evaporation and drying. (5)

17. An aqueous phase autocatalytic reaction, A + R → R + R is conducted in an isothermal batch reactor with certain initial concentration of R. Suggest a reactor configuration for this reaction (plug flow, mixed flow or combination of mixed flow and plug flow) which will give the lowest total volume of the reactor under the following condition. Justify your answer with appropriate graphical representation of performance equation.
(a) Plot the rate of reaction (− rA ) against concentration (CA) for this
reaction.
(b) If the conversion is lower, say 40%.
(c) If the conversion is higher, say 90%. (5)

18. (a) Two reactors, one with zero dispersion and the second with infinite
dispersion are placed in series. If the residence times of the reactors are τ 1 and τ 2 . Sketch the residence time distribution, E(t) of the reactors in series.
(b) A pulse tracer is introduced into the fluid entering a reaction vessel
having a volume of 1 m3 and flow rate 1 m3/min. The concentration of the tracer measured in the fluid leaving the vessel is shown below. Find the flow model parameters that fit the measured RTD in terms of one or all of the mixing element namely, volume of plug flow reactor Vp, mixed flow volume VM, and the dead space VD. (5)

19. (a) Define Thiele modulus φ and discuss its significance in an isothermal
solid catalysed reaction.
(b) A first order isothermal catalytic reaction A → R, occurs in an
infinitely long cylindrical pore. How the effectiveness factor is related to Thiele modulus. (5)

20. In an enzymatic reaction, the substrate (S) bind with the enzyme (E) and produce the product (P). Let [S] be the concentration of S and –rs be the rate of consumption of S.
(a) Write the form of rate expression and the mechanism proposed by
Michaelis-Menten to explain the enzyme fermentation reaction.
(b) How to evaluate the two rate constants of the enzyme fermentation
from the –rs versus [S] graph. (5)

21. A tank has a slotted weir whose outflow mass rate w is proportional to liquid level h to the 1.5 power: w = Rh¹·⁵. If a single stream enters with mass rate wᵢ, find the transfer function relating change in height to change in input mass flow rate. Identify gain and time constant and verify units. Cross-sectional area is A and density is constant. (5)

22. Consider the block diagram shown in the figure.
Y (s )
(a) Find the order of the overall transfer function relating G (s ) = .
X (s )
(b) Find the gain, poles, and zeros of G (s ) and the location of poles on the
complex s plane.
(c) What condition(s) will one or more of the zeros be located in the
right-half s-plane?
(d) For any bounded input, is the output bounded? Justify your answer. (5)

23. Using a Routh array, determine the stability of the feedback system shown, where G_p = 1/(12s + 1), G_v = 1/(6s + 1), G_m = 1/(s + 1), and G_c = K_c. (5)

24. The set-point of a proportional-control system with K_c = 2.0 undergoes a step change of magnitude 2. For G_p = 5/[(s + 1)(2s + 1)], (a) determine the closed-loop transfer function and (b) determine the offset. (5)

25. List and briefly explain five methods used for estimating capital investment. (5)

26. Give the basic mathematical formula for Discounted Cash Flow (DCF). Also discuss two major advantages and two critical limitations of using DCF as a valuation tool. (5)

27. Explain the concept of optimum reflux ratio in a distillation column. How does the selection of reflux ratio influence the column height, diameter and overall equipment cost? (5)

28. The book value of a reactor decreases uniformly every year. Identify the depreciation method, provide its mathematical formulation and state its primary advantages and disadvantages. (5)

29. Prepare an engineering flow sheet for the manufacture of sulphuric acid by single absorption contact process. (5)

30. Explain the following related to petroleum coking process :
(a) Influence of the process variables temperature and pressure.
(b) Three distinct types of coking units. (5)

31. Explain the low-pressure Ziegler polymerization process used in the manufacture of polyethylene. (5)

32. List five major engineering problems encountered during the production of urea through ammonium carbamate decomposition. (5)

33. Define lapse rate and discuss the effect of lapse rate on dispersion of gases emitted from a stack. (5)

34. A water sample contains 100 mg/lit of Ca2+ and 24 mg/lit Mg2+. Express hardness of this water sample as milliequivalent/lit and mg/lit of CaCO 3. Equivalent weight of Calcium ion is 20 and that of Magnesium ion is 12. (5)

35. Landfilling is one of the most widely used methods for the disposal of solid wastes. Explain various stages of decomposition process in a landfill. (5)

36. In water treatment plants, trivalent metallic salts are typically added to achieve chemical coagulation. Explain four possible mechanisms by which coagulation is accomplished. (5)

37. Describe the theory of fire extinguishing. Suppose a fire is detected in a room that stores sensitive measuring and control equipment. Suggest a fire extinguisher which is suitable to deal with fires in this room. Justify your answer. (5)

38. What are the causes for runaway reactions? Describe the essential requirements to prevent runaway reactions. (5)

39. How are industrial hazardous zones classified? Explain. (5)

40. Distinguish between event tree and fault tree analysis. Explain the advantages and disadvantages of fault tree analysis. (5)