1. The resistance equation for the cold fluid is R = __________
a) 1/hcAc
b) 1/hcAT
c) hcAc
d) hcAT
Explanation: The resistance on the cold side is equal to the convective resistance to the colder side having area Ac and coefficient hc. Hence resistance = 1/hcAc
2. What is the term N in the following equation?
NRe = Reynolds number for agitated liquids = (LA2 × N × ρB / μB).
a) Agitator Speed
b) Number of turns in coil
c) Number of turns in jacket coil
d) Number of passes in jacket
Explanation: In the Reynolds number for agitated liquids, we consider the total liquid volume that passes a particular point in some period of time, for which we require the agitator speed in RPM. Hence the term N is number of turns the agitator makes in specific period of time.
3. If ADC is the fouling deposit area on the vessel side, then what is its resistance?
a) R = 1/hADC
b) R = 1/hDCADC
c) R = 1/hDCAT
d) R = 1/hTADC
Explanation: The resistance of the surface is due to the covering fouled area only which has a heat transfer coefficient of hDC. Hence the correct expression is R = 1/hDCADC.
4. If the Nusselt Number for the jacket side is calculated then what is the definition of Dj?
NNu = Nusselt number of jacket fluid = (hJ * DJ / kJ).
a) Diameter of jacket tubes
b) Equivalent cross flow diameter of the jacket
c) Diameter of the vessel
d) Difference of the diameter of jacket and vessel
Explanation: The term Dj stands for the equivalent cross flow diameter of the jacket which is slightly greater than the vessel diameter and is equal to the closed surface transferring heat.
5. What is the term Γ in the following equation?
NRe Film = Reynolds number for the condensate film.
NRe Film = 4Γ / μJ
a) Condensate loading rate
b) Condensate removing rate
c) Vapour Removal rate
d) Vapour Loading rate
Explanation: The term given above is defined as the condensate loading rate which is measured as the mass rate of condensate per perimeter of vessel jacket.
6. Packed bed reactors are ________ heat exchangers.
a) Indirect Contact
b) Direct Contact
c) Tubular
d) Plate-type
Explanation: Packed bed HE are usually direct contact HE where the liquid and gas phase come directly in contact through the bed to transfer heat. Whereas the heat transfer in packed bed reactors is indirect contact type.
7. Which one of the following is not a use of packed bed?
a) Regenerators
b) Stripping
c) Mixing
d) Solid matrix heat exchangers
Explanation: Packed beds are used in applications such as separators, absorbers, stripping, reactors absorption, regenerators, thermal insulations, grain storage, and solid matrix heat exchangers.
8. Why is heating or cooling required in packed beds if we don’t use it as a heat exchanger?
a) To Cool Exothermic reactions
b) To cool water by using ice as pellets
c) To cool petroleum by using ice as pellets
d) To heat exothermic reactions
Explanation: One of the important use of packed beds is to heat endothermic reactions and also cool exothermic reactions by using it in a shell and tube arrangement.
9. It has been found that wall-cooled operations on packed beds show more effective heat transfer rate than wall-heated operations.
a) True
b) False
Explanation: Yes, it has been experimentally proved that wall-cooled operations on packed beds are more effective than wall-heated operations because of minute heat loss in wall-heated operations.
10. Wall heated packed beds and wall cooled both have more or less the same correlations.
a) True
b) False
Explanation: Earlier when the number of experiments conducted was less, the correlations were regarded to be same for the two operations, but later it was found that wall-cooled operations on packed beds show more effective heat transfer rate than wall-heated operations, hence the correlations were changed.