Climbing film evaporator is a key unit operation in pharmaceutical processing that concentrates solutions by forming a thin liquid film on heated vertical tubes. This introduction explains the principle, construction, and working of climbing (rising) film evaporators, plus common uses, merits, and demerits relevant to B.Pharm students. You will learn how feed distribution, steam heating, vapor-liquid separation, and short residence time affect heat transfer, fouling, and product quality. Keywords: climbing film evaporator, rising film evaporator, principle, construction, working, uses, merits, demerits, MCQs, B.Pharm. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary principle behind the operation of a climbing (rising) film evaporator?
- Capillary action draws liquid upwards without vapor formation
- Vapor formation drives liquid to form a thin film that rises along heated tubes
- Mechanical pumps force the liquid up while steam heats it
- Gravity pulls liquid down while heating occurs externally
Correct Answer: Vapor formation drives liquid to form a thin film that rises along heated tubes
Q2. In a climbing film evaporator, where is the feed typically introduced?
- At the top of the tubes
- At the shell side inlet
- At the bottom of the tubes
- Directly into the vapor-liquid separator
Correct Answer: At the bottom of the tubes
Q3. What component separates vapor and liquid in a climbing film evaporator?
- Condenser
- Feed distributor
- Vapor-liquid separator (flash chamber)
- Rotary wiper
Correct Answer: Vapor-liquid separator (flash chamber)
Q4. Which heating medium is commonly used in the shell side of climbing film evaporators?
- Cooling water
- Hot oil or steam
- Refrigerant gas
- Ambient air
Correct Answer: Hot oil or steam
Q5. A major advantage of climbing film evaporators is:
- High residence time for thorough heating
- Low heat transfer coefficient
- Short residence time and high heat transfer rate
- Ability to process extremely high-viscosity feeds without issues
Correct Answer: Short residence time and high heat transfer rate
Q6. Climbing film evaporators are best suited for which type of feed?
- Highly viscous and high solids slurries
- Low to moderate viscosity and low fouling feeds
- Pure solids
- Gaseous reactants
Correct Answer: Low to moderate viscosity and low fouling feeds
Q7. Which of the following is a common demerit of climbing film evaporators?
- They have extremely long residence times
- They require very high vacuum levels for all applications
- Not suitable for very viscous or high-solid feeds due to poor film formation
- They cannot be cleaned in place (CIP)
Correct Answer: Not suitable for very viscous or high-solid feeds due to poor film formation
Q8. In a climbing film evaporator, the driving force for evaporation is primarily:
- Mechanical agitation
- Temperature difference (ΔT) between heating medium and boiling liquid
- Electrical heating inside tubes
- Magnetic stirring
Correct Answer: Temperature difference (ΔT) between heating medium and boiling liquid
Q9. How does vapor velocity affect film formation in a climbing film evaporator?
- Higher vapor velocity prevents film formation entirely
- Vapor velocity has no effect on film formation
- Adequate vapor velocity helps lift the liquid film up the tubes
- Lower vapor velocity always improves film uniformity
Correct Answer: Adequate vapor velocity helps lift the liquid film up the tubes
Q10. Which part of the climbing film evaporator removes condensed vapor?
- Feed distributor
- Bottom drain
- Condenser connected to vapor outlet
- Steam trap
Correct Answer: Condenser connected to vapor outlet
Q11. Compared to a falling film evaporator, a climbing film evaporator generally:
- Performs better with very viscous feeds
- Relies on vapor generation to create upward flow
- Has lower heat transfer coefficients
- Always requires a rotating wiper
Correct Answer: Relies on vapor generation to create upward flow
Q12. Which operational parameter directly influences heat transfer coefficient in climbing film evaporators?
- Feed color
- Tube surface area only
- Liquid film thickness and fluid flow regime
- Ambient humidity
Correct Answer: Liquid film thickness and fluid flow regime
Q13. What is the typical flow regime inside the tubes of a climbing film evaporator?
- Plug flow without phase change
- Rising two-phase (vapor-liquid) flow forming a thin film
- Pure single-phase liquid laminar flow
- Solid suspension flow
Correct Answer: Rising two-phase (vapor-liquid) flow forming a thin film
Q14. Which maintenance issue is most likely in climbing film evaporators processing pharmaceuticals?
- Excessive electrical corrosion of internal motors
- Fouling or scaling on tube walls reducing heat transfer
- Degradation of cooling water quality only
- Complete inability to separate vapor and liquid
Correct Answer: Fouling or scaling on tube walls reducing heat transfer
Q15. Which advantage makes climbing film evaporators attractive for heat-sensitive pharmaceutical products?
- Long heating times at high temperatures
- Short residence time limiting thermal degradation
- Requirement for aggressive agitation
- Extremely high pressure operation
Correct Answer: Short residence time limiting thermal degradation
Q16. Where is the steam typically introduced in a climbing film evaporator?
- Into the vapor-liquid separator
- Directly into the product stream
- On the shell side surrounding the tube bundle
- Into the condenser
Correct Answer: On the shell side surrounding the tube bundle
Q17. Increasing the overall heat transfer coefficient (U) in a climbing film evaporator will:
- Reduce the evaporation rate
- Increase the required heating area for a given duty
- Increase evaporation rate or reduce required heating area
- Have no effect on performance
Correct Answer: Increase evaporation rate or reduce required heating area
Q18. Which phenomenon can cause entrainment losses in a climbing film evaporator?
- Very low vapor velocities
- Excessive foaming and high vapor carry-over
- Use of vacuum operation only
- Low feed temperature
Correct Answer: Excessive foaming and high vapor carry-over
Q19. For scale-up of climbing film evaporators, a critical parameter to maintain is:
- Tube color
- Mass velocity or vapor velocity to ensure film formation
- Length of external piping only
- Ambient room size
Correct Answer: Mass velocity or vapor velocity to ensure film formation
Q20. Which cleaning method is commonly used for pilot and production climbing film evaporators in pharma plants?
- Dry ice blasting only
- Cleaning-in-place (CIP) with appropriate solvents and detergents
- Immersion in molten salt
- No cleaning is required
Correct Answer: Cleaning-in-place (CIP) with appropriate solvents and detergents
Q21. The vapor-liquid separator in a climbing film evaporator is located:
- Below the tube bundle
- At the top of the tube bundle
- Outside the evaporator system entirely
- Inside each individual tube
Correct Answer: At the top of the tube bundle
Q22. What is one common use of climbing film evaporators in pharmaceutical manufacturing?
- Dry milling of powders
- Concentration of dilute aqueous drug solutions and solvent recovery
- Final tablet coating
- Sterilization by autoclaving
Correct Answer: Concentration of dilute aqueous drug solutions and solvent recovery
Q23. Which heat transfer mechanism predominates in climbing film evaporators?
- Radiation only
- Conduction through solids only
- Convection and boiling heat transfer at the liquid film interface
- Advection in gas phase only
Correct Answer: Convection and boiling heat transfer at the liquid film interface
Q24. Operating climbing film evaporators under vacuum is done primarily to:
- Increase boiling point and processing temperature
- Allow boiling at lower temperatures to protect heat-sensitive products
- Eliminate the need for a condenser
- Reduce vapor production entirely
Correct Answer: Allow boiling at lower temperatures to protect heat-sensitive products
Q25. Which control parameter is vital to avoid tube dry-out in a climbing film evaporator?
- Feed flow rate to maintain adequate film thickness
- Color of the vessel
- Ambient lighting conditions
- Motor RPM of external pumps only
Correct Answer: Feed flow rate to maintain adequate film thickness
Q26. How does fouling affect performance of a climbing film evaporator?
- Improves heat transfer and reduces energy costs
- Has no measurable effect
- Increases thermal resistance and reduces evaporator efficiency
- Increases vapor production automatically
Correct Answer: Increases thermal resistance and reduces evaporator efficiency
Q27. Which geometry is typical for the tube bundle in a climbing film evaporator?
- Horizontal U-tubes only
- Vertical straight tubes
- Spiral coils inside the shell only
- Plate stacks without tubes
Correct Answer: Vertical straight tubes
Q28. What is the role of feed preheating in climbing film evaporator operation?
- Preheating is never used as it causes fouling
- Preheating reduces temperature driving force required and improves overall energy efficiency
- Preheating increases viscosity dramatically
- Preheating solidifies the feed
Correct Answer: Preheating reduces temperature driving force required and improves overall energy efficiency
Q29. Which operational sign indicates insufficient vapor generation in a climbing film evaporator?
- Excessive liquid carryover at the vapor outlet
- Very high vapor velocity with no liquid discharge
- No change in feed concentration downstream
- Excessively high product temperature only
Correct Answer: No change in feed concentration downstream
Q30. For processing solutions that foam, what is a recommended practice in climbing film evaporators?
- Increase feed temperature to promote more foaming
- Add antifoam agents and design separators to handle foam
- Eliminate condensers to reduce foam
- Operate at atmospheric pressure only
Correct Answer: Add antifoam agents and design separators to handle foam
Q31. Which equation or correlation is often used to estimate evaporation rates or heat transfer in film evaporators?
- Nernst equation
- Reynolds and heat transfer correlations (e.g., Dittus-Boelter, Sieder-Tate) adapted for two-phase flow
- Planck’s radiation law only
- Ideal gas law exclusively
Correct Answer: Reynolds and heat transfer correlations (e.g., Dittus-Boelter, Sieder-Tate) adapted for two-phase flow
Q32. Which is an operational advantage of multiple-effect climbing film evaporator trains?
- Higher steam consumption per kilogram evaporated
- Reduced specific steam usage by reusing vapor as heating media across effects
- Increased residence time in each effect dramatically
- Less efficient thermal economy
Correct Answer: Reduced specific steam usage by reusing vapor as heating media across effects
Q33. What is the expected effect of increasing feed concentration on climbing film performance?
- Always improves film formation
- May increase viscosity, risk of fouling, and reduce evaporation rate per area
- Has no impact on heat transfer
- Eliminates the need for a condenser
Correct Answer: May increase viscosity, risk of fouling, and reduce evaporation rate per area
Q34. Which safety consideration is important when operating climbing film evaporators with organic solvents?
- Ensure good ventilation and explosion-proof equipment due to flammable vapor
- Operate at high oxygen concentration intentionally
- Use open flames for steam generation near the vessel
- No special precautions needed compared to water
Correct Answer: Ensure good ventilation and explosion-proof equipment due to flammable vapor
Q35. How is product discharge typically performed in a climbing film evaporator?
- Through the top vapor outlet
- From the bottom liquid outlet after vaporization and separation
- By evaporating the entire feed to dryness
- Through steam traps only
Correct Answer: From the bottom liquid outlet after vaporization and separation
Q36. Why might a pharmaceutical process prefer a falling film evaporator over a climbing film evaporator?
- Falling film cannot handle heat-sensitive materials
- Falling film has lower residence time and gentler handling for extremely heat-sensitive products
- Falling film always uses less surface area than climbing film
- Falling film requires no condensers
Correct Answer: Falling film has lower residence time and gentler handling for extremely heat-sensitive products
Q37. In plate-type climbing film evaporators, what replaces the tubular bundle?
- Horizontal trays only
- Flat plates or plate channels designed to form films
- A rotating screw conveyor
- Woven mesh packing
Correct Answer: Flat plates or plate channels designed to form films
Q38. Which parameter directly reduces the likelihood of tube scaling in climbing film evaporators?
- Increasing temperature differences dramatically
- Effective pre-treatment of feed to remove scale-forming ions
- Operating with lower steam pressure always
- Using smaller diameter tubes exclusively
Correct Answer: Effective pre-treatment of feed to remove scale-forming ions
Q39. Which design modification can help handle slightly higher viscosity feeds in climbing film evaporators?
- Decrease tube length to zero
- Increase vapor velocity or use mechanical circulation to assist film formation
- Operate at extremely low temperatures only
- Eliminate the vapor-liquid separator
Correct Answer: Increase vapor velocity or use mechanical circulation to assist film formation
Q40. What is a common symptom of inadequate heat transfer area in a climbing film evaporator?
- Lower-than-target concentration of the product leaving the unit
- Excessive cooling of heating medium
- No vapor generation at all conditions
- Immediate boiling to dryness
Correct Answer: Lower-than-target concentration of the product leaving the unit
Q41. Which instrument is essential for monitoring evaporator performance by indicating concentration?
- pH meter only
- Refractometer or density meter
- Thermometer only
- Colorimeter exclusively
Correct Answer: Refractometer or density meter
Q42. In climbing film evaporators, increasing the number of effects primarily aims to:
- Reduce capital cost always
- Improve thermal economy by reusing vapor for heating subsequent effects
- Increase steam consumption per kg evaporated
- Decrease overall plant capacity
Correct Answer: Improve thermal economy by reusing vapor for heating subsequent effects
Q43. Which is a correct statement about energy efficiency of climbing film evaporators?
- They are always less efficient than single-effect batch evaporators
- Multiple-effect climbing film systems can have high thermal efficiency
- They consume no energy if operated at atmospheric pressure
- Energy efficiency is independent of effect count
Correct Answer: Multiple-effect climbing film systems can have high thermal efficiency
Q44. What happens when the feed temperature is too low entering the climbing film evaporator?
- Evaporation increases unexpectedly
- May reduce evaporation rate and cause inadequate film formation
- Film becomes thinner automatically and improves heat transfer
- No impact on vapor generation
Correct Answer: May reduce evaporation rate and cause inadequate film formation
Q45. Which operating condition favors formation of a more uniform thin film?
- Very low heat flux and stagnant vapor
- Adequate vapor generation with uniform feed distribution
- Non-uniform feed entry at the top of tubes
- Extreme superheating without boiling
Correct Answer: Adequate vapor generation with uniform feed distribution
Q46. Which of the following best describes a climbing film evaporator’s suitability for solvent recovery?
- Unsuitable because they cannot separate solvent vapors
- Suitable because they produce vapors that can be condensed and recovered efficiently
- Only suitable for non-volatile solvents
- Suitable only if the solvent is solid at room temperature
Correct Answer: Suitable because they produce vapors that can be condensed and recovered efficiently
Q47. What effect does scale layer on tube walls have on required heating surface area?
- It reduces required area by improving conduction
- It increases required area because heat transfer resistance rises
- No effect on required area
- Eliminates need for a condenser
Correct Answer: It increases required area because heat transfer resistance rises
Q48. Which parameter is used to express thermal driving force in evaporators?
- pH difference
- Temperature difference (ΔT) between heating medium and boiling liquid
- Color difference of feed
- Optical density
Correct Answer: Temperature difference (ΔT) between heating medium and boiling liquid
Q49. If a climbing film evaporator is operating with excessive foaming, which downstream problem might occur?
- Higher product purity automatically
- Liquid carryover into vapor line and condenser contamination
- Complete halt of vapor production only
- Reduction in feed viscosity
Correct Answer: Liquid carryover into vapor line and condenser contamination
Q50. Which operational strategy helps maintain consistent concentration in continuous climbing film evaporation?
- Constant steam pressure and controlled feed flow with proper level control in separator
- Random variations of feed and steam supply
- Closing the condenser intermittently
- Allowing uncontrolled foaming to set the level
Correct Answer: Constant steam pressure and controlled feed flow with proper level control in separator
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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