chemical engineering heat transfer chemical engineering MCQs – Page 22

Practise multiple-choice questions from chemical engineering heat transfer chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering heat transfer chemical engineering Mcqs

421. Economy of a multiple effect evaporator is not influenced much by the_______________________?
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A. Ratio of the weight of the thin liquor to thick liquor

B. Rate of heat transfer

C. Boiling point elevations

D. Temperature of the feed

422. For a cold dilute feed to produce thick viscous liquor, backward feeding as compared to forward feeding results in_____________________?
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A. Increased economy

B. Decreased economy

C. No effect on economy

D. Lower capacity

423. The advantage of backward feed multiple effect evaporators over forward feed units is that___________________?
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A. Heat sensitive material can be handled

B. Most concentrated liquid is at highest temperature

C. Equal heat transfer co-efficients exist in various effects

D. There is no additional cost of pumping

424. Reynolds analogy states that_________________?
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A. NRe ? f

B. NNu ? f

C. Nst ? f

D. Nst ? NRe

425. For gases, the thermal conductivity increases with temperature rise. For liquids, with increase in concentration, its thermal conductivity generally ?
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A. Remains unchanged

B. Decreases

C. Increases exponentially

D. Increases

426. Dittus-Boelter equation cannot be used for molten metals mainly due to its very low_____________________?
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A. Thermal conductivity

B. Prandtl number

C. Viscosity

D. Grashoff number

427. Fouriers law applies to the heat transfer by__________________?
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A. Radiation

B. All A., B. & C.

C. Conduction

D. Convection

428. In case of evaporators, liquid entrainment results primarily due to_________________?
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A. High evaporation rate

B. High vacuum in the evaporator

C. Foaming of the solution

D. High heat transfer rate

429. With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer ?
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A. Remain unaffected

B. Increases exponentially

C. Increases

D. Decreases

430. Electromagnetic radiations propagate in vacuum with a velocity of _______________ metre/second?
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A. 3 1012

B. 3 1010

C. 3 108

D. 3 105

431. A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is__________________?
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A. 6000

B. 48000

C. 60000

D. 24000

432. Circulation pump is located below the evaporator to___________________?
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A. Avoid cavitation

B. None of these

C. Avoid frequent priming

D. Create more suction head

433. Baffles in the shell side of a shell and tube heat exchanger ?
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A. Decrease the shell side heat transfer co-efficient

B. Force the liquid to flow parallel to the bank

C. Increase the shell side heat transfer co-efficient

D. Increase the cross-section of the shell side liquid

434. Multiple effect evaporators ar used to___________________?
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A. Increase the steam economy & decrease the capacity

B. Decrease the steam economy & increase the capacity

C. Decrease the steam economy & the capacity

D. Increase the steam economy & the capacity

435. If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length________________?
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A. ha = hl

B. ha = 0.5 hl

C. ha = 2hl

D. ha = 0.75 hl

436. In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of___________________?
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A. Chemical potentials

B. Activity co-efficients

C. Mass transfer co-efficients

D. Concentrations

437. In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always__________________?
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A. > 1

B. ?

C. 1

D. < 1

438. Steam is routed through the tube in case of a ______________ evaporator?
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A. Long tube vertical

B. Short tube vertical

C. Basket type

D. Horizontal tube

439. Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for_________________?
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A. Equal for all the three

B. Cylinder

C. Cube

D. Sphere

440. Air is best heated with steam in a heat exchanger of__________________?
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A. Double pipe type with fin on steam side

B. Shell and tube type

C. Double pipe type with fin on air side

D. Plate type

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