1. What are the factors to be considered for designing a heat exchanger?
a) Thermal analysis
b) Hydraulic calculations
c) Pressure calculations
d) Thermal analysis and hydraulic calculations
Discussion
Explanation: There are 2 factors to be considered for designing a heat exchanger. They are Thermal analysis and hydraulic calculations. The thermal analysis is a study of the physical and chemical properties of the fluid with respect to temperature under controlled temperature program. Hydraulic analysis refers to the study of fluid under different conditions.
2. Are these statements about the regenerative heat exchangerstrue?
Statement 1: Regenerators are commonly used in gas/gas heat recovery applications.
Statement 2: Regenerative heat exchangers are also known as capacitive heat exchangers.
a) True, False
b) True, True
c) False, True
d) False, False
Discussion
Explanation: Regenerative heat exchangers are also known as capacitive heat exchangers. The flow path consists of the matrix where heat from the hot fluid is captured in the matrix and then it is released to the cold fluid. Regenerators are commonly used in gas/gas heat recovery applications mainly in power stations. Static and dynamic are the two types of regenerators.
3.What are main advantages of continuous heat exchanger over batch heat exchanger?
a) Efficiency and cost
b) Quantity and cost
c) Efficiency and quality
d) Efficiency and quantity
Discussion
Explanation: The two important merits of continuous heat exchanger over batch heat exchanger are efficiency and quantity. The efficiency of the continuous heat exchanger depends on the continuous cleaning and calibration. The quantity depends on the feed rate which is higher than the batch process. But continuous heat exchanger is expensive than a batch system.
4. Which of the following statements about two-phase heat exchangers are correct?
Statement 1: Two-phase heat exchangers undergo phase change during the heat transfer process.
Statement 2: It is used mainly in water-to-water heat transfer applications.
a) True, False
b) True, True
c) False, True
d) False, False
Discussion
Explanation: Two-phase heat exchangers undergo phase change during the heat transfer process. The phase change occurs in either or both the fluids thus resulting in liquid to gas or gas to liquid change. The two-phase heat exchangers includecondensers, boilers and evaporators.
5. The deposition of any undesired material on heat transfer surfaces is called _____________
a) fouling
b) debris
c) scaling
d) rubble
Discussion
Explanation: The deposition of any undesired material on heat transfer surfaces is called fouling. It refers to the deposit collected on the surfaces of the heat exchanger. It contains organic particles, inorganic particles, microorganisms. This increases the risk of corrosion.
6. Which is the common fouling mechanism seen when untreated water is used as the coolant?
a) Biological Fouling
b) Chemical Fouling
c) Corrosion Fouling
d) Freezing Fouling
Discussion
Explanation: Biological Fouling is due to the microorganisms present on heat transfer surfaces. It is a common fouling mechanism seen when untreated water is used as the coolant. A variety range from algae to other microbes can be seen. These microbes are grow into colonies within hours, restricting heat transfer.
7. ___________ results from a chemical reaction involving the heat exchanger surface material.
a) Biological Fouling
b) Chemical Fouling
c) Corrosion Fouling
d) Freezing Fouling
Discussion
Explanation: Corrosion fouling results from a chemical reaction involving the heat exchanger surface material.Biological Fouling is due to the microorganisms present on heat transfer surfaces. Chemical fouling results from chemical reactions of fluid that causes deposition of material on the surface of the heat exchanger. Freezing fouling is seen when one of the component in hot fluid is cooled to near freezing point.
8. Is heat exchanger and condenser are same?
a) True
b) False
Discussion
Explanation: Heat exchanger is the equipment which is used to recover the heat and also transfer of heat takes place in between two fluids. The heat is transferred without any phase change. A condenser is the equipment where the vapor is condensed and converted into liquid. In condenser along with the transfer of heat, phase change also takes place.
9. What is the purpose of the portholes on the plates of plate heat exchangers?
a) To have a even flow of the fluid throughout the plate
b) To drain the excess liquid from the plate
c) To maintain the pressure inside the heat exchanger
d) To stack the plates
Discussion
Explanation: The main purpose of the portholes on the plates of plate heat exchangers is to ensure that flow of the liquid is even throughout the plate. It also increases the heat transfer efficiency and reduces the fouling.
10. The corrugation of V shape embossed on the plates is termed as _______________
a) reflex angle
b) V angle
c) Z angle
d) chevron angle
Discussion
Explanation: The corrugation of V shape engraved on the plates is known aschevron angle. It is measured with horizontal direction. This is normally used to produce the turbulence effect to the flow.