chemical engineering heat transfer chemical engineering MCQs – Page 21

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 Review each marked answer and report any item that may be outdated or unclear.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

401. The rate of heat transfer through a pipe wall is given by, q = 2? k (Ti T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?
0

A. q = 2? k (Ti T0)/(r0/ri)

B. q = 2? ri k (Ti T0)/(r0/ri)

C. q = [2? k (Ti + T0)/2]/ln (ri/r0)

D. q = 2? k (Ti T0)/[(r0 + ri)/2]

402. A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case ?
0

A. The cooling rate will be the same for the two spheres and hence the two spheres will have

B. al temperatures at any instant

C. Both the spheres will emit equal amount of radiation per unit time in the beginning

D. Both will absorb equal amount of radiation from the surrounding in the beginning

E. Both B. & C.

403. Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.) ?
0

A. ?d

B. d1.5

C. d

D. d2

404. Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by__________________?
0

A. Conduction

B. Eddies current

C. Convection

D. None of these

405. At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the___________________?
0

A. Buffer zone

B. Turbulent core

C. Both A. and B.

D. Viscous sub-layer

406. 1 BTU/hr.ft.F is equal to _____________ kcal/hr. m.C?
0

A. None of these

B. 1

C. 4.88

D. 1.49

407. Baffle spacing ____________________?
0

A. Should be less than one fifth the diameter of the shell

B. Should be less than the inside diameter of the shell

C. None of these

D. Is not the same as baffle pitch

408. The ratio of kinematic viscosity to thermal diffusivity is called the _______________ number?
0

A. Peclet

B. Nusselt

C. Stanton

D. Prandtl

409. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is______________?
0

A. Dependent on NRe only

B. 3.66

C. 88.66

D. 1.66

410. The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) ?
0

A. h0/2K

B. K/h0

C. 2K/h0

D. h0/K

411. Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is __________________?
0

A. None of these

B. Uniformly distributed throughout the fluid

C. In the central core of the fluid

D. Mainly confined to a thin film of fluid near the surface

412. Pick out the wrong statement?
0

A. Steam jet ejector is used for vapor compression in a thermal recompression evaporator

B. Heat sensitive materials should be concentrated in high pressure evaporators

C. The capacity of an evaporator is reduced by the boiling point elevation

D. Corrosive liquid is normally passed through the tubes in a shell and tube heat exchanger

413. Heat transfer occurs by natural convection because change in temperature causes difference in__________________?
0

A. Thermal conductivity

B. Viscosity

C. Heat capacity

D. Density

414. The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m2. The approximate surface temperature (K) is (Stefan-Boltzmann constant = 5.67 10-8 W/m2.K4) ?
0

A. 800

B. 1000

C. 727

D. 1200

415. The type of liquor circulation system to be employed in evaporators (viz. natural or forced circulation) is determined mainly by the ______________ of the liquid?
0

A. Viscosity

B. Thermal conductivity

C. Corrosive nature

D. Density

416. The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by__________________?
0

A. Painting the surface black

B. Giving the surface a mirror finish

C. Roughening the surface

D. Painting the surface white (with aluminium paint)

417. In an extended surface heat exchanger, fluid having lower co-efficient________________?
0

A. Should not be used as it gives very high pressure drop

B. Flows outside the tubes

C. Can flow either inside or outside the tubes

D. Flows through the tube

418. In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is_________________?
0

A. Infinity

B. Same as average heat transfer co-efficient for tube side

C. None of these

D. Zero

419. Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) ?
0

A. E/C

B. C/E

C. 1/CE

D. CE

420. Thermal diffusivity is given by__________________?
0

A. ?Cp/a

B. k/?Cp

C. ?/hCp

D. ?Cp/k

Previous Next

Showing 401 to 420 of 511 mcqs