This set of Heat Transfer Operations Multiple Choice Questions & Answers (MCQs) focuses on “Dryers – General Overview”.
1. A dryer is an equipment used to remove ___________
a) Salt
b) Moisture
c) Fluids
d) Entrapped gases
View Answer
Explanation: A dryer is equipment that removes moisture from crystals/ solids / other substances possibly by dehydration, desiccation, dewatering and heating etc.
2. There are three principal factors that define the nature of a dryer, which one of the following is not?
a) The method of material conveyance through the drying section
b) The pressure and temperature of operation
c) Humidity of the atmosphere
d) The method of heating the material
View Answer
Explanation: The three factors upon which the dryer operation depends are –
- The method of material conveyance through the drying section
- The pressure and temperature of operation
- The method of heating the material
3. The method of conveyance of the feed through the dryer is not very important as a particular operation setup can handle all types of feed.
a) True
b) False
View Answer
Explanation: The method of conveying the feed through the dryer is one of the most important factor that governs the outward appearance of a dryer and limits its operating parameters.
4. Handling of awkward materials like loose fibres, which can tangle together, and very wet sticky feeds can be done by considering which one of the following factor?
a) The method of material conveyance through the drying section
b) The pressure and temperature of operation
c) Humidity of the atmosphere
d) The method of heating the material
View Answer
Explanation: The method of conveying the feed through the dryer is one of the most important factor that governs the outward appearance of a dryer and limits its operating parameters. While free-flowing small particles can be handled in a variety of ways, weird materials like loose fibres, which may tangle together, and very wet sticky feeds require special techniques.
5. Which one of the following is not a method of conveyance of feed?
a) Closed heap
b) Through-circulated heap
c) Cross-circulated layers on trays
d) Fluidized heap
View Answer
Explanation: The common methods of conveyance are-
- A large tile kept exposed
- Through-circulated packing
- Cross-ventilated layers on plates
- Fluidized pack
- Agitated pan
6. Drying methods can be classified as two processes, they are?
a) Batch and Continuous
b) Free falling and closed
c) Free and forced convection
d) Nucleate and non-nucleate heating
View Answer
Explanation: Yes, there are mainly two common ways to classify drying processes as Batch and continuous according to the way of supplying the feed which can be done as a particular set of batches, or a continuous flow of feed type operation.
7. Which one of the following is not a type of continuous drying method?
a) Circulated band dryer
b) Vibrated-band dryer
c) Fluidised Bed
d) Suction-drum dryer
View Answer
Explanation: Continuous-drying methods with undisturbed or cascading solids are of the following setups. They are circulated band dryer, vibrated-band dryer, suction-drum dryer, rotary cascading dryer, multi-tubular rotary cascading dryer, through-circulation rotary dryer.
8. A _____________ dryer will require less labour, fuel and floor space than a __________ dryer of the same capacity.
a) Continuous, Batch
b) Batch, continuous
c) Packed, batch
d) Batch, packed
View Answer
Explanation: The continuous dryer because of its continuous operation will require less labour, fuel and floor space than a batch dryer of the same capacity. Packed bed is a batch dryer.
9. ___________ drying would be chosen whenever the production rate is small (under 200 kg/hr).
a) Rotary dryer
b) Drum dryer
c) Continuous
d) Batch
View Answer
Explanation: Batch dryers are always preferred for small feed quantities under 200kg/hr or minor more or less quantities. All the other options are of continuous feed dryers which take continuous supply of feed materials throughout their operation period.
10. ___________ drying would be chosen whenever large number of product have to be handled in the same unit.
a) Rotary dryer
b) Drum dryer
c) Continuous
d) Batch
View Answer
Explanation: Batch dryers are always preferred for small feed quantities as well as for the situation when large number of products have to be handled at the same unit. All the other options are of continuous feed dryers.
11. Dryers particularly heat the feed by ____________
a) Direct methods
b) Indirect methods
c) Indirectly or Directly-heated.
d) Direct Fire contact
View Answer
Explanation: Dryers can be used with furnaces, microwaves, induction heaters as well as with superheated steam. Hence they can be heated by both indirectly or directly.
12. Drying can take place by which of the following processes?
a) Radiation
b) Conduction
c) Convection
d) By any one or all the means simultaneously
View Answer
Explanation: Dryers can be used with furnaces, microwaves, induction heaters as well as with superheated steam. Hence they can be heated by any one or all the means simultaneously be it conduction, convection or radiation.
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