Heat exchangers - Test
  • 1. Which type of heat exchanger uses a set of parallel tubes to transfer heat?
A) Finned tube
B) Double-pipe
C) Shell and tube
D) Plate
  • 2. Which material is commonly used for the construction of heat exchanger tubes?
A) Steel
B) Aluminum
C) Copper
D) Plastic
  • 3. What is used to enhance heat transfer in a heat exchanger by increasing surface area?
A) Fins
B) Gaskets
C) Valves
D) Bearings
  • 4. What is the function of the header in a shell and tube heat exchanger?
A) Control temperature
B) Separate hot and cold fluids
C) Reduce pressure
D) Distribute the fluid evenly to the tubes
  • 5. What is the purpose of the bypass valve in a heat exchanger system?
A) Control flow rate through the exchanger
B) Regulate pressure
C) Remove air from the system
D) Increase heat transfer
  • 6. What is the function of the expansion valve in a refrigeration system?
A) Cool the refrigerant
B) Remove moisture from the system
C) Increase the pressure of the refrigerant
D) Regulate the flow of refrigerant into the evaporator
  • 7. What helps maintain efficient heat transfer by preventing fouling in a heat exchanger?
A) Regular cleaning and maintenance
B) Increased pressure
C) Higher flow rate
D) Less insulation
  • 8. What is meant by the term 'heat exchanger fouling'?
A) Decrease in fluid velocity
B) Accumulation of deposits on heat transfer surfaces
C) Increase in heat transfer rate
D) Expansion of tube material
  • 9. In which flow arrangement do the two fluids enter the exchanger from opposite ends?
A) Cross-flow
B) Direct-contact
C) Counter-flow
D) Parallel-flow
  • 10. What is the driving temperature difference across a heat exchanger surface called?
A) Heat transfer coefficient
B) Net thermal unit (NTU)
C) Log mean temperature difference (LMTD)
D) Thermal resistance
  • 11. Which flow arrangement in heat exchangers involves fluids traveling roughly perpendicular to one another?
A) Direct-contact
B) Parallel-flow
C) Counter-flow
D) Cross-flow
  • 12. What is a common type of shell-and-tube heat exchanger used for cooling air?
A) Plate heat exchanger
B) Evaporator
C) Surface condenser
D) Double-pipe heat exchanger
  • 13. Which of the following is NOT a typical application for shell and tube heat exchangers?
A) Processes involving fluids at temperatures greater than 260 °C.
B) High-pressure applications greater than 30 bar.
C) Low-pressure applications with temperatures below 260 °C.
D) Applications requiring robust construction due to high pressure.
  • 14. What is a critical consideration when determining tube thickness in shell and tube heat exchangers?
A) Reducing the availability of spare parts.
B) Ensuring enough room for corrosion resistance.
C) Maximizing the flow-induced vibration.
D) Minimizing the axial strength.
  • 15. What is the expected annual growth rate of the global demand for heat exchangers?
A) 15% annually.
B) About 5% annually.
C) 1% annually.
D) 10% annually.
  • 16. How can pillow plates be constructed inside a tank?
A) Using flexible rubber sheets
B) By embedding them in concrete
C) Through external attachment
D) As flat plates that are stacked inside a tank
  • 17. Which method for designing helical-coil heat exchangers is from the United States?
A) Laminar flow method
B) Ramachandra K. Patil (et al.) method
C) Scott S. Haraburda method
D) Boardman-Germer method
  • 18. What is the advantage of using U-tubes in shell and tube heat exchangers?
A) They increase the likelihood of fouling.
B) They eliminate the need for baffles.
C) They allow for thermal expansion without stressing the tubesheets.
D) They reduce the overall size of the heat exchanger.
  • 19. What patterns may plates in a plate heat exchanger have?
A) Circular patterns
B) Square grids
C) No patterns at all
D) Chevron, dimpled, or other patterns
  • 20. What is the typical hydraulic diameter of channels in microchannel heat exchangers?
A) Between 1mm and 3mm
B) Smaller than 1mm
C) Larger than 5mm
D) Equal to 10mm
  • 21. In HVAC applications, what is a large plate heat exchanger called?
A) Circular plate pack
B) Shell and tube
C) Welded plate variety
D) Plate-and-frame
  • 22. What is the primary application of a pillow plate heat exchanger in the dairy industry?
A) Fermenting yogurt
B) Heating milk before pasteurization
C) Storing cheese
D) Cooling milk in large direct-expansion stainless steel bulk tanks
  • 23. Which type of direct contact heat exchanger involves heat transfer between gas and liquid?
A) Solid-liquid or solid – gas
B) Microchannel
C) Gas – liquid
D) Immiscible liquid – liquid
  • 24. What is the purpose of the outer shell in a plate and shell heat exchanger?
A) Creates a second flowpath called the 'Shell side'
B) Holds the gaskets
C) Is used for cleaning purposes
D) Contains only the Plate side flowpath
  • 25. Which cycle is typically used in large systems with high volume and temperature gas streams?
A) Dynamic scraped surface heat exchanger.
B) Organic Rankine cycle (ORC).
C) Phase-change heat exchanger.
D) Steam Rankine cycle (SRC).
  • 26. Which of the following is NOT typically used as an organic refrigerant in ORC?
A) Water.
B) Pentafluoropropane (R-245fa).
C) Toluene.
D) Ammonia.
  • 27. Which method for designing helical-coil heat exchangers originates from India?
A) Turbulent flow method
B) Ramachandra K. Patil (et al.) method
C) Scott S. Haraburda method
D) Boardman-Germer method
  • 28. Which industry commonly uses plate and fin heat exchangers for low temperature services?
A) Chemical manufacturing
B) Nuclear power plants
C) Oil refineries
D) Air separation plants
  • 29. In which industry is a pillow plate heat exchanger commonly used?
A) Textile industry
B) Dairy industry
C) Construction industry
D) Automotive industry
  • 30. What material are plate and fin heat exchangers usually made of?
A) Aluminum alloys
B) Stainless steel
C) Titanium
D) Copper
  • 31. What is the primary criterion often considered when selecting a heat exchanger?
A) Cost.
B) Shape.
C) Size.
D) Color.
  • 32. What is a notable tradeoff in heat exchanger design?
A) Pressure drop vs fluid velocity.
B) Capital cost vs operating cost.
C) Material strength vs corrosion resistance.
D) Thermal efficiency vs size.
  • 33. What happens to the thin metal after welding in pillow plate construction?
A) It becomes thinner and more flexible
B) It is removed to create channels
C) It contracts and forms a flat surface
D) It bulges out around the welds when pressurized
  • 34. What is a key characteristic of microchannel heat exchangers compared to finned tube heat exchangers?
A) Larger size
B) Higher refrigerant charges
C) Lower airside pressure drops
D) Less compact
  • 35. What is a potential danger associated with cracked heat exchangers in direct-combustion furnaces?
A) Airflow will increase significantly.
B) Combustion products may enter living space.
C) The furnace will produce less heat.
D) The system will become more energy-efficient.
  • 36. What is a significant concern for HVAC designers regarding water or steam coils?
A) Microchannel design
B) Low refrigerant charges
C) High pressure drops
D) Freeze protection
  • 37. Which tube layout is preferred when high fouling is expected?
A) Triangular (30°) pattern.
B) Rotated square (45°) pattern.
C) Rotated triangular (60°) pattern.
D) Square (90°) pattern.
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