# Food Processing Unit Operations Questions and Answers – Heat Transfer Applications – Plate Heat Exchangers

This set of Food Processing Unit Operations Multiple Choice Questions & Answers (MCQs) focuses on “Heat Transfer Applications – Plate Heat Exchangers”.

1. 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

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.

2. The corrugation of V shape embossed on the plates is termed as _______________
a) reflex angle
b) V angle
c) Z angle
d) chevron angle

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.

3. Which heat exchanger is most efficient?
a) Parallel flow
b) Cross flow
c) Counter flow
d) Tangent flow

Explanation: A counterflow heat exchanger works on the principle that the hot fluid enters at one end of the exchanger and thecold fluid enters at the other end. Counter flow is the widely used in liquid-liquid heat exchanger, as it is the most efficient flow compared to others.

4. Are these statements about the heat exchangerstrue?
Statement 1: In parallel flow, the temperature difference between the two fluids is large at the entrance end, but it becomes small at the exit end.
Statement 2: The log mean temperature difference is greater for parallel flow.
a) True, False
b) True, True
c) False, True
d) False, False

Explanation: In parallel flow, both the fluids enter at one end and exit at the other end.the temperature difference between the two fluids is large at the entrance end, but it becomes small at the exit end. The log mean temperature difference is greater for counter flow. So the surface area of the parallel flow heat exchanger should be larger than for a counter flow heat exchanger.

5. Air conditioner evaporator coil uses _______ in the heat exchanger.
a) parallel flow
b) cross flow
c) counter flow
d) tangent flow

Explanation: Car radiator and air conditioner evaporator coil uses crossflow heat exchangers. Crossflow heat exchangers are widely used for transfer of heat between a gas and a liquid. In air conditioner evaporator coil, the air flows past the evaporator coils are cooled by the cold refrigerant that is flowing inside the tubes of the coil.

6. What is main advantage of Brazed Plate Heat Exchanger?
a) Thermal efficiency
b) Quality
c) Leak proof
d) Easy cleaning

Explanation: A Brazed Plate Heat Exchanger has the highest level of thermal efficiency and durability, low-cost unit. It also works under high temperature and pressure conditions. It is used in boilers, heat pumps, district heating, domestic water, radiant, air conditioners.

7. In ________, pressure is applied in between the plates.
a) pillow plate exchangers
b) plate fin exchangers
c) plate and shell heat exchangers
d) spiral plate heat exchangers

Explanation: In pillow plate exchangers, pressure is applied in between the plates. This is an additional benefit to increase the heat transfer efficiency across the surface of the plate.

8. Which exchanger is called as modified floating-head shell-and-tube exchanger?
a) Pillow plate exchangers
b) Plate fin exchangers
c) Lamella plate heat exchangers
d) Spiral plate heat exchangers

Explanation: Lamella plate heat exchanger is called as modified floating-head shell-and-tube exchanger. One fluid flows inside the lamella whereas the other flows longitudinally in the spaces between them. There are no baffles on the shell side. The flow arrangement is generally counter flow.

9. What method is used to manufacture panel coils?
a) Die stamping process
b) 3 D printing process
c) Cold bonding process
d) Hot bonding process

Explanation: Die stamping process is usedfor manufacturing panel coils. In this process, flow channels are die stamped on either one or two metal sheets. When one sheet is engraved and joined to a flatplate, it forms a one-sided embossed panelcoil. When both sheets are stamped, it forms a double sidedembossed panelcoil. Finally the two plates are joined by electric resistance welding.

10. _______ are also referred toas a matrix heat exchanger.
a) Pillow plate exchangers
b) Plate fin exchangers
c) Lamella plate heat exchangers
d) Spiral plate heat exchangers

Explanation: Plate fin exchanger is also referred to as a matrix heat exchanger. In this heat exchanger, layers of corrugated sheets are made which is separated by flat metal plates therefore creating a series of finned chambers. The hot and cold fluid streams flow in alternate layers of the heat exchanger.

Sanfoundry Global Education & Learning Series – Food Processing Unit Operations.

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