Introduction: Understanding the mechanisms of heat transfer is essential for B.Pharm students involved in drug formulation, sterilization, drying, and storage. This concise guide covers conduction, convection, and radiation with practical emphasis on pharmaceutical processes—tablet coating, freeze-drying, spray drying, and autoclave sterilization. You will learn key concepts such as thermal conductivity, convective heat transfer coefficients, Newton’s law of cooling, Stefan–Boltzmann law, Biot number, and the lumped-capacitance approach, all tailored to drug manufacturing and stability. The material links theory to equipment design, process control, and product quality to help you solve real-world thermal problems in pharmaceutics. ‘Now let’s test your knowledge with 50 MCQs on this topic.’
Q1. What is the primary mechanism of heat transfer through a solid dosage tablet during hot air drying?
- Conduction through the tablet matrix
- Convection from the air to the tablet
- Radiation from dryer walls
- Mass diffusion of solvent
Correct Answer: Conduction through the tablet matrix
Q2. Fourier’s law describes which aspect of heat transfer?
- Heat flux proportional to temperature gradient
- Convective heat transfer coefficient dependence
- Radiative heat emission from a blackbody
- Latent heat during phase change
Correct Answer: Heat flux proportional to temperature gradient
Q3. Which mode of heat transfer dominates in vacuum freeze-drying (lyophilization)?
- Conduction through shelf and product
- Convection from gas to product
- Radiation from chamber walls
- Mass diffusion only
Correct Answer: Conduction through shelf and product
Q4. Newton’s law of cooling relates convective heat transfer to which variables?
- Heat flux, convective coefficient, and temperature difference
- Thermal conductivity and temperature gradient
- Emissivity and absolute temperature to the fourth power
- Specific heat and mass
Correct Answer: Heat flux, convective coefficient, and temperature difference
Q5. Which property best describes a material’s ability to conduct heat?
- Thermal conductivity
- Specific heat capacity
- Thermal diffusivity
- Viscosity
Correct Answer: Thermal conductivity
Q6. In forced convection drying of granules, increasing air velocity primarily affects which parameter?
- Convective heat transfer coefficient
- Thermal conductivity of the product
- Specific heat of the air
- Latent heat of solvent
Correct Answer: Convective heat transfer coefficient
Q7. Stefan–Boltzmann law is used to quantify which type of heat transfer?
- Thermal radiation from a surface
- Conduction through a wall
- Convective heat exchange
- Mass transfer of vapor
Correct Answer: Thermal radiation from a surface
Q8. The Biot number (Bi) compares which two resistances?
- Internal conductive resistance to external convective resistance
- Radiative to convective resistance
- Mass transfer resistance to heat transfer resistance
- Latent heat resistance to sensible heat resistance
Correct Answer: Internal conductive resistance to external convective resistance
Q9. For which Biot number condition is the lumped capacitance method valid?
- Bi < 0.1
- Bi > 10
- Bi ≈ 1
- Bi between 0.5 and 2
Correct Answer: Bi < 0.1
Q10. Which parameter describes how quickly a material responds to temperature changes?
- Thermal diffusivity
- Thermal conductivity
- Specific heat capacity
- Density only
Correct Answer: Thermal diffusivity
Q11. In tablet coating, heat transfer is important to control which outcome?
- Solvent evaporation rate and film formation
- Pore size distribution in the tablet core
- Chemical compatibility of excipients
- Tablet hardness unrelated to temperature
Correct Answer: Solvent evaporation rate and film formation
Q12. Which of the following increases radiative heat transfer from a heated surface?
- Higher emissivity
- Lower surface temperature
- Reduced surface area
- Low Stefan–Boltzmann constant
Correct Answer: Higher emissivity
Q13. What role does latent heat play in pharmaceutical drying?
- Energy required for phase change (evaporation) of solvent
- Heat required to raise temperature without phase change
- Heat lost by radiation only
- It is negligible in spray drying
Correct Answer: Energy required for phase change (evaporation) of solvent
Q14. Which heat transfer mode is most significant during autoclave sterilization of liquids?
- Convection within the liquid and conduction through container walls
- Radiation from chamber surfaces
- Conduction only through the autoclave air
- Mass diffusion of steam into liquid
Correct Answer: Convection within the liquid and conduction through container walls
Q15. Emissivity is a measure of what property?
- Ability of a surface to emit thermal radiation relative to a blackbody
- Convective heat transfer strength
- Thermal resistance of a wall
- Specific heat per unit mass
Correct Answer: Ability of a surface to emit thermal radiation relative to a blackbody
Q16. Which dimensionless number characterizes the relative importance of momentum and thermal diffusivity in convection?
- Prandtl number
- Reynolds number
- Nusselt number
- Biot number
Correct Answer: Prandtl number
Q17. Nusselt number correlates to which physical quantity in convective heat transfer?
- Enhancement of convective heat transfer relative to conduction
- Ratio of inertial to viscous forces
- Convective flux per unit mass
- Radiative heat flux magnitude
Correct Answer: Enhancement of convective heat transfer relative to conduction
Q18. During spray drying, which heat transfer process primarily evaporates solvent from droplets?
- Convective heat transfer from hot air to droplets
- Radiative heating from walls
- Conduction between droplets
- Phase conduction within the drying chamber
Correct Answer: Convective heat transfer from hot air to droplets
Q19. Which factor does NOT directly affect conductive heat transfer through a homogeneous slab?
- External air velocity far from the slab
- Thermal conductivity of the slab
- Slab thickness
- Temperature difference across the slab
Correct Answer: External air velocity far from the slab
Q20. Thermal resistance of a composite wall in series is calculated by:
- Summing individual layer resistances
- Multiplying conductivities of layers
- Inversely summing conductances in parallel only
- Using only the highest resistance layer
Correct Answer: Summing individual layer resistances
Q21. Which heat transfer mode becomes negligible in well-evacuated pharmaceutical packaging?
- Convection
- Conduction through solids
- Radiation between surfaces
- Internal heat generation
Correct Answer: Convection
Q22. In drying kinetics, the constant rate period is controlled by which process?
- External mass and heat transfer to the surface
- Diffusion of moisture from the interior
- Chemical degradation reactions
- Crystallization of solutes
Correct Answer: External mass and heat transfer to the surface
Q23. Which of these materials generally has the highest thermal conductivity?
- Metal (e.g., stainless steel)
- Polymers
- Air
- Expanded foam
Correct Answer: Metal (e.g., stainless steel)
Q24. The term “heat flux” refers to:
- Rate of heat transfer per unit area
- Total heat transferred over time
- Temperature difference across a material
- Thermal resistance multiplied by area
Correct Answer: Rate of heat transfer per unit area
Q25. Which technique measures thermal conductivity of a powder or granule bed?
- Hot plate or guarded hot plate method
- Titration
- UV-Vis spectrophotometry
- HPLC
Correct Answer: Hot plate or guarded hot plate method
Q26. In convective boiling for heat removal, what greatly enhances heat transfer?
- Vigorous bubble formation and turbulence
- Low surface roughness only
- Reduced liquid flow rate
- Insulating the heating surface
Correct Answer: Vigorous bubble formation and turbulence
Q27. The Arrhenius equation relates reaction rate to temperature. Which heat transfer concern is directly linked to this in pharmaceuticals?
- Temperature control to limit thermal degradation of drugs
- Enhancing radiative heating for sterilization
- Improving conduction through packaging
- Modifying airflow patterns only
Correct Answer: Temperature control to limit thermal degradation of drugs
Q28. Which is the correct unit for thermal conductivity in SI?
- W/m·K
- J/kg
- W/m2
- K/W
Correct Answer: W/m·K
Q29. In laminar boundary layer over a flat plate, how does heat transfer coefficient change with distance from the leading edge?
- It decreases with distance due to growth of thermal boundary layer
- It increases linearly with distance
- It remains constant
- It oscillates periodically
Correct Answer: It decreases with distance due to growth of thermal boundary layer
Q30. For a spherical particle, which simplifies transient conduction analysis when internal resistance is small?
- Lumped capacitance method
- Using Stefan–Boltzmann law
- Assuming pure radiation transfer
- Neglecting external convection
Correct Answer: Lumped capacitance method
Q31. Which process relies heavily on radiative heat transfer in pharmaceutical drying?
- Infrared-assisted drying of surface coatings
- Vacuum freeze-drying of bulk solution
- Conventional convective tray drying exclusively
- Isothermal storage
Correct Answer: Infrared-assisted drying of surface coatings
Q32. Thermal contact resistance between a tablet and a shelf affects which operation most directly?
- Heat conduction during tray drying
- Radiative heat exchange in a vacuum
- Mass transfer coefficient of air
- Solubility of API
Correct Answer: Heat conduction during tray drying
Q33. Which heat transfer coefficient would a pharmaceutical engineer adjust to speed up cooling of a reactor jacket?
- Convective heat transfer coefficient on the cooling side
- Emissivity of reactor walls
- Specific heat capacity of the product only
- Latent heat of reactants
Correct Answer: Convective heat transfer coefficient on the cooling side
Q34. Which situation increases convective heat transfer in storage rooms?
- Using fans to promote forced convection
- Sealing the room to prevent airflow
- Adding vacuum insulation
- Reducing temperature gradients only
Correct Answer: Using fans to promote forced convection
Q35. Which statement about radiative heat transfer between two surfaces is true?
- It depends on surface temperatures, areas, view factors and emissivities
- It only depends on convection coefficients
- It is independent of surface geometry
- It can be ignored at all typical pharmaceutical temperatures
Correct Answer: It depends on surface temperatures, areas, view factors and emissivities
Q36. In designing a drying oven, which property of the product most directly affects drying time?
- Thermal diffusivity and moisture diffusivity of the product
- Molecular weight of the API only
- Color of the product exclusively
- Packaging label design
Correct Answer: Thermal diffusivity and moisture diffusivity of the product
Q37. Which is an important consideration when using hot melt granulation regarding heat transfer?
- Controlling temperature to avoid API melting or degradation
- Maximizing radiative heat only
- Eliminating all convection in the granulator
- Using materials with lowest possible thermal conductivity
Correct Answer: Controlling temperature to avoid API melting or degradation
Q38. Which heat transfer mechanism dominates in thermal conduction through a hollow glass vial wall?
- Conduction through the glass material
- Convection inside the glass material
- Radiation through the glass only
- Mass transfer across the wall
Correct Answer: Conduction through the glass material
Q39. What effect does adding a vacuum layer have in insulated pharmaceutical containers?
- It greatly reduces convective and conductive heat transfer
- It increases conduction across the container
- It enhances radiative heat transfer only
- It makes thermal conductivity of air higher
Correct Answer: It greatly reduces convective and conductive heat transfer
Q40. Which dimensionless number is most directly used to correlate convective heat transfer coefficients?
- Nusselt number
- Prandtl number only
- Biot number exclusively
- Péclet number only
Correct Answer: Nusselt number
Q41. In conductive heat transfer through multilayer tablet coatings, which parameter must be considered for each layer?
- Thermal conductivity and thickness of each coating layer
- Only the outermost layer’s color
- Solubility of API only
- Relative humidity only
Correct Answer: Thermal conductivity and thickness of each coating layer
Q42. Which is a practical method to improve heat transfer in freeze-drying shelves?
- Improve thermal contact between product trays and shelves
- Reduce chamber vacuum to atmospheric pressure
- Use thicker trays to insulate product
- Minimize shelf temperature differences intentionally
Correct Answer: Improve thermal contact between product trays and shelves
Q43. In conduction, heat transfer through a cylindrical pipe wall depends on:
- Logarithmic function of inner and outer radii and thermal conductivity
- Linear difference of radii only
- Square of the wall thickness only
- Viscosity of the fluid inside only
Correct Answer: Logarithmic function of inner and outer radii and thermal conductivity
Q44. For a given heating surface, increasing surface roughness typically does what to convective heat transfer?
- Can increase heat transfer by promoting turbulence
- Always decreases heat transfer
- Has no effect on heat transfer
- Eliminates radiative transfer
Correct Answer: Can increase heat transfer by promoting turbulence
Q45. Which is true about thermal stability testing in pharmaceutical storage?
- Temperature control and heat transfer determine degradation rates
- Only light exposure matters, not temperature
- Heat transfer is irrelevant for solid dosage forms
- Higher thermal conductivity always protects API stability
Correct Answer: Temperature control and heat transfer determine degradation rates
Q46. Which heat transfer consideration is important when designing a heat exchanger for solvent recovery?
- Corrosion resistance, fouling, and overall heat transfer coefficient
- Only the color of the exchanger shell
- Neglecting flow arrangement
- Maximizing pressure drop irrespective of heat transfer
Correct Answer: Corrosion resistance, fouling, and overall heat transfer coefficient
Q47. Why is the concept of heat capacity important for batch reactors?
- It determines how much energy is needed to change reactor temperature
- It determines radiative emissivity only
- It is irrelevant for exothermic reactions
- It solely defines pressure changes
Correct Answer: It determines how much energy is needed to change reactor temperature
Q48. Which approach helps prevent hot spots during drying of large pharmaceutical batches?
- Ensure uniform airflow and load distribution to enhance convective transfer
- Use intermittent heating with no airflow
- Place product only at chamber corners
- Rely solely on radiation from heating elements
Correct Answer: Ensure uniform airflow and load distribution to enhance convective transfer
Q49. The Q10 rule estimates how reaction rates change with a 10°C temperature increase. This is relevant to heat transfer because:
- Small temperature rises can significantly change degradation rates
- Heat transfer coefficients always change by Q10
- It describes radiative emission changes only
- It replaces the need to control temperature
Correct Answer: Small temperature rises can significantly change degradation rates
Q50. In evaluating thermal design for cold chain logistics, which factor is least relevant?
- API color in the formulation
- Insulation thermal resistance of packaging
- Ambient convective conditions during transport
- Heat load from internal product warming
Correct Answer: API color in the formulation
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.
Mail- Sachin@pharmacyfreak.com