Important questions about Heat Transfer Basics. Heat Transfer Basics MCQ questions with answers. Heat Transfer Basics exam questions and answers for students and interviews.

The following equation, corresponds to __________ analogy.

Options

A : a. Von-Karmann

B : b. Reynolds

C : c. Colburn

D : d. Prandtl

Out of the following four assumptions used in the derivation of the equation for LMTD given by below equation, which one is subject to the largest deviation in practice ?

Options

A : a. Constant overall heat transfer co-efficient.

B : b. Constant rate of fluid flow.

C : c. Constant specific heat.

D : d. No partial phase change in the system.

For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

Options

A : a. A

B : b. B

C : c. C

D : d. D

The Dietus-Boelter equation for convective heat transfer given by following equation, cannot be used for

Options

A : a. low Reynold's number

B : b. very low Grashoff number

C : c. molten metals

D : d. all (a), (b) and (c)

The rate of heat transfer through a pipe wall is given by following equation. For cylinder of very thin wall, q can be approximated by

Options

A : a. A

B : b. B

C : c. C

D : d. D

At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below. The thermal conductivity of material I

Options

A : a. is smaller than that of II.

B : b. is greater than that of II.

C : c. is equal to that of II.

D : d. can be greater than or smaller than that of II.

In case of surface condensers, a straight line is obtained on plotting 1/U vs __________ on an ordinary graph paper.

Options

A : a. A

B : b. B

C : c. C

D : d. D

Fouling factor for a heat exchanger is given by (where, U? = heat transfer co-efficient of dirty surface U? = heat transfer co-efficient of clean surface)

Options

A : a. A

B : b. B

C : c. C

D : d. D

For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy

Options

A : a. A

B : b. B

C : c. C

D : d. D

Following number is called the __________ number.

Options

A : a. Peclet

B : b. Stanton

C : c. Graetz

D : d. none of these

The following equation is the __________ analogy.

Options

A : a. Colburn

B : b. Reynolds

C : c. Prandtl

D : d. None of these

The number given below is termed as the __________ number.

Options

A : a. Grashoff

B : b. Nusselt

C : c. Prandtl

D : d. Stanton

Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by following equation. This is valid for the value of NRe equal to

Options

A : a. < 2100

B : b. 2100-4000

C : c. > 4000

D : d. > 10000

Hot water (0.01 m³ /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m³/min) of density 800 kg/m³ and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately

Options

A : a. 32

B : b. 37

C : c. 45

D : d. 50

A process stream of dilute aqueous solution flowing at the rate of10 Kg.s?¹ is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s?¹. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

Options

A : a. counter flow with process stream on shell side.

B : b. counter flow with process stream on tube side.

C : c. parallel flow with process stream on shell side.

D : d. parallel flow with process stream on tube side.

A 10 cm diameter steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m².°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be

Options

A : a. greater than that for uninsulated steam pipe.

B : b. less than that of the uninsulated steam pipe.

C : c. equal to that of the uninsulated steam pipe.

D : d. less than the steam pipe with 5 cms insulation.

The thermal radiation emitted by a body is proportional to T?, where T is its absolute temperature. The value of 'n' is exactly 4 for

Options

A : a. black painted bodies only

B : b. all bodies

C : c. polished bodies only

D : d. a black body

LMTD for counterflow and prallel flow heat exchanger will be the same, when the

Options

A : a. cold fluid is heated to a certain temperature by condensing steam (isothermal fluid).

B : b. outlent temperature of both the hot and cold fluid are same.

C : c. outlet temperature of hot fluid is less than the outlet temperature of the cold fluid.

D : d. none of these.

The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.

Options

A : a. increases

B : b. decreases

C : c. remains constant

D : d. may increase or decrease ; depends on the material