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