Heat exchangers - Test
  • 1. Which type of heat exchanger uses a set of parallel tubes to transfer heat?
A) Plate
B) Shell and tube
C) Finned tube
D) Double-pipe
  • 2. Which material is commonly used for the construction of heat exchanger tubes?
A) Copper
B) Steel
C) Plastic
D) Aluminum
  • 3. What is used to enhance heat transfer in a heat exchanger by increasing surface area?
A) Valves
B) Fins
C) Gaskets
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) Distribute the fluid evenly to the tubes
D) Reduce pressure
  • 5. What is the purpose of the bypass valve in a heat exchanger system?
A) Remove air from the system
B) Regulate pressure
C) Increase heat transfer
D) Control flow rate through the exchanger
  • 6. What is the function of the expansion valve in a refrigeration system?
A) Remove moisture from the system
B) Increase the pressure of the refrigerant
C) Regulate the flow of refrigerant into the evaporator
D) Cool the refrigerant
  • 7. What helps maintain efficient heat transfer by preventing fouling in a heat exchanger?
A) Increased pressure
B) Less insulation
C) Higher flow rate
D) Regular cleaning and maintenance
  • 8. What is meant by the term 'heat exchanger fouling'?
A) Expansion of tube material
B) Increase in heat transfer rate
C) Accumulation of deposits on heat transfer surfaces
D) Decrease in fluid velocity
  • 9. In which flow arrangement do the two fluids enter the exchanger from opposite ends?
A) Parallel-flow
B) Counter-flow
C) Cross-flow
D) Direct-contact
  • 10. What is the driving temperature difference across a heat exchanger surface called?
A) Log mean temperature difference (LMTD)
B) Net thermal unit (NTU)
C) Heat transfer coefficient
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) Surface condenser
B) Double-pipe heat exchanger
C) Evaporator
D) Plate 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) Applications requiring robust construction due to high pressure.
C) High-pressure applications greater than 30 bar.
D) Low-pressure applications with temperatures below 260 °C.
  • 14. What is a critical consideration when determining tube thickness in shell and tube heat exchangers?
A) Maximizing the flow-induced vibration.
B) Reducing the availability of spare parts.
C) Ensuring enough room for corrosion resistance.
D) Minimizing the axial strength.
  • 15. What is the expected annual growth rate of the global demand for heat exchangers?
A) 10% annually.
B) 1% annually.
C) About 5% annually.
D) 15% annually.
  • 16. How can pillow plates be constructed inside a tank?
A) By embedding them in concrete
B) As flat plates that are stacked inside a tank
C) Through external attachment
D) Using flexible rubber sheets
  • 17. Which method for designing helical-coil heat exchangers is from the United States?
A) Ramachandra K. Patil (et al.) method
B) Boardman-Germer method
C) Laminar flow method
D) Scott S. Haraburda method
  • 18. What is the advantage of using U-tubes in shell and tube heat exchangers?
A) They allow for thermal expansion without stressing the tubesheets.
B) They reduce the overall size of the heat exchanger.
C) They increase the likelihood of fouling.
D) They eliminate the need for baffles.
  • 19. What patterns may plates in a plate heat exchanger have?
A) No patterns at all
B) Square grids
C) Circular patterns
D) Chevron, dimpled, or other patterns
  • 20. What is the typical hydraulic diameter of channels in microchannel heat exchangers?
A) Smaller than 1mm
B) Larger than 5mm
C) Between 1mm and 3mm
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) Heating milk before pasteurization
B) Fermenting yogurt
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) Holds the gaskets
B) Contains only the Plate side flowpath
C) Creates a second flowpath called the 'Shell side'
D) Is used for cleaning purposes
  • 25. Which cycle is typically used in large systems with high volume and temperature gas streams?
A) Phase-change heat exchanger.
B) Steam Rankine cycle (SRC).
C) Organic Rankine cycle (ORC).
D) Dynamic scraped surface heat exchanger.
  • 26. Which of the following is NOT typically used as an organic refrigerant in ORC?
A) Toluene.
B) Ammonia.
C) Pentafluoropropane (R-245fa).
D) Water.
  • 27. Which method for designing helical-coil heat exchangers originates from India?
A) Scott S. Haraburda method
B) Ramachandra K. Patil (et al.) method
C) Turbulent flow 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) Air separation plants
D) Chemical manufacturing
  • 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) Aluminum alloys
B) Titanium
C) Stainless steel
D) Copper
  • 31. What is the primary criterion often considered when selecting a heat exchanger?
A) Cost.
B) Shape.
C) Color.
D) Size.
  • 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 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) Larger size
B) Less compact
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) The furnace will produce less heat.
B) The system will become more energy-efficient.
C) Airflow will increase significantly.
D) Combustion products may enter living space.
  • 36. What is a significant concern for HVAC designers regarding water or steam coils?
A) Microchannel design
B) Freeze protection
C) High pressure drops
D) Low refrigerant charges
  • 37. Which tube layout is preferred when high fouling is expected?
A) Rotated triangular (60°) pattern.
B) Triangular (30°) pattern.
C) Rotated square (45°) pattern.
D) Square (90°) pattern.
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