Question 1

Depending on the radiating properties, a body will be white when (where a = absorptivity, p = reflectivity, x = transmissivity)

Accepted Answer

A) p = 0, x = 0 and a = 1 
B) p=l,T = 0anda = 0 
C) p = 0, x = 1 and a = 0 
D) x = 0, a + p = 1 
E) a = 0, x + p = 1. 
A) p = 0, x = 0 and a = 1 
B) p=l,T = 0anda = 0 
C) p = 0, x = 1 and a = 0 
D) x = 0, a + p = 1 
E) a = 0, x + p = 1. B

Question 2

For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it

Accepted Answer

A) Decreases the pressure drop 
B) Decreases the outlet temperature of cooling medium 
C) Increases the overall heat transfer coefficient 
D) None of these 
A) Decreases the pressure drop 
B) Decreases the outlet temperature of cooling medium 
C) Increases the overall heat transfer coefficient 
D) None of these C

Question 3

Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.

Accepted Answer

A) 1 
B) 10 
C) 20 
D) 30 
A) 1 
B) 10 
C) 20 
D) 30 A

Question 4

Planck's law holds good for

Accepted Answer

A) black bodies 
B) polished bodies 
C) all coloured bodies 
D) all of the above 
E) none of the above. 
A) black bodies 
B) polished bodies 
C) all coloured bodies 
D) all of the above 
E) none of the above.

Question 5

A grey body is one whose absorptivity

Accepted Answer

A) varies with temperature 
B) varies with the wave length of incident ray 
C) varies with both 
D) does not vary with temperature and wave length of the incident ray 
E) there is no such criterion. 
A) varies with temperature 
B) varies with the wave length of incident ray 
C) varies with both 
D) does not vary with temperature and wave length of the incident ray 
E) there is no such criterion.

Question 6

The ratio of the energy absorbed by the body to total energy falling on it is called

Accepted Answer

A) absorptive power 
B) emissive power 
C) absorptivity 
D) emissivity 
E) none of the above. 
A) absorptive power 
B) emissive power 
C) absorptivity 
D) emissivity 
E) none of the above.

Question 7

Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by

Accepted Answer

A) convection 
B) free convection 
C) forced convection 
D) radiation 
E) radiation and convection. 
A) convection 
B) free convection 
C) forced convection 
D) radiation 
E) radiation and convection.

Question 8

For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

Accepted Answer

A) 1.26 h1 
B) 0.794 h1 
C) 0.574 h1 
D) 1.741 h1 
A) 1.26 h1 
B) 0.794 h1 
C) 0.574 h1 
D) 1.741 h1

Question 9

Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer coefficient is „3k/l'. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade?

Accepted Answer

A) 35.5 
B) 43.75 
C) 81.25 
D) 48.25 
A) 35.5 
B) 43.75 
C) 81.25 
D) 48.25

Question 10

The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit

Accepted Answer

A) temperature 
B) thickness 
C) area 
D) time 
E) area and time. 
A) temperature 
B) thickness 
C) area 
D) time 
E) area and time.

Question 11

40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

Accepted Answer

A) 0.45 
B) 0.55 
C) 0.40 
D) 0.75 
E) 0.60. 
A) 0.45 
B) 0.55 
C) 0.40 
D) 0.75 
E) 0.60.

Question 12

In regenerator type heat exchanger, heat transfer takes place by

Accepted Answer

A) direct mixing of hot and cold fluids 
B) a complete separation between hot and cold fluids 
C) flow of hot and cold fluids alternately over a surface 
D) generation of heat again and again 
E) indirect transfer. 
A) direct mixing of hot and cold fluids 
B) a complete separation between hot and cold fluids 
C) flow of hot and cold fluids alternately over a surface 
D) generation of heat again and again 
E) indirect transfer.

Question 13

Absorptivity of a body will be equal to its emissivity

Accepted Answer

A) at all temperatures 
B) at one particular temperature 
C) when system is under thermal equi-librium 
D) at critical temperature 
E) for a polished body. 
A) at all temperatures 
B) at one particular temperature 
C) when system is under thermal equi-librium 
D) at critical temperature 
E) for a polished body.

Question 14

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

Accepted Answer

A) Black painted bodies only 
B) All bodies 
C) Polished bodies only 
D) A black body 
A) Black painted bodies only 
B) All bodies 
C) Polished bodies only 
D) A black body

Question 15

Depending on the radiating properties, a body will be black when (where a = absorptivity, p == reflectivity, X = transmissivity.)

Accepted Answer

A) p = 0, x = 0 and a = 1 
B) p= l,T = 0anda = 0 
C) p = 0, x = 1 and a = 0 
D) x = 0, a + p = 0 
E) a = 0,x + p= 1. 
A) p = 0, x = 0 and a = 1 
B) p= l,T = 0anda = 0 
C) p = 0, x = 1 and a = 0 
D) x = 0, a + p = 0 
E) a = 0,x + p= 1.

Question 16

Depending on the radiating properties, a body will be opaque when (where a = absorptivity, p = reflectivity, X = transmissivity.)

Accepted Answer

A) p = 0, x = 0 and a = 1 
B) p=l,x = 0anda = 0 
C) p = 0, x = 1 and a = 0 
D) x - 0, a + p = 1 
E) a=0,x + p= 1. 
A) p = 0, x = 0 and a = 1 
B) p=l,x = 0anda = 0 
C) p = 0, x = 1 and a = 0 
D) x - 0, a + p = 1 
E) a=0,x + p= 1.

Question 17

A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun?

Accepted Answer

A) Yellow paint 
B) White paint 
C) Black paint 
D) Grey paint 
A) Yellow paint 
B) White paint 
C) Black paint 
D) Grey paint

Question 18

If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of

Accepted Answer

A) 3 
B) 6 
C) 9 
D) 27 
E) 81. 
A) 3 
B) 6 
C) 9 
D) 27 
E) 81.

Question 19

According to Wien's law, the wavelength corresponding to maximum energy is proportion to

Accepted Answer

A) absolute temperature (T) 
B) I2  
C) f 
D) t 
E) 1/r. 
A) absolute temperature (T) 
B) I2  
C) f 
D) t 
E) 1/r.

Question 20

Depending on the radiating properties, body will be transparent when

Accepted Answer

A) p = 0, x = 0 and a = 1 
B) p=l,x = 0,anda = 0 
C) p = 0, T= l,anda = 0 
D) X = 0, a + p = 1 
E) a = 0,x + p= 1. 
A) p = 0, x = 0 and a = 1 
B) p=l,x = 0,anda = 0 
C) p = 0, T= l,anda = 0 
D) X = 0, a + p = 1 
E) a = 0,x + p= 1.

Exam 18: Heat Transfer Mechanisms in a Spaced Plate System

Depending on the radiating properties, a body will be white when (where a = absorptivity, p = reflectivity, x = transmissivity)

For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it

Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second.

Planck's law holds good for

A grey body is one whose absorptivity

The ratio of the energy absorbed by the body to total energy falling on it is called

Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by

For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit

40% of incident radiant energy on the surface of a thermally transparent body is reflected back. If the transmissivity of the body be 0.15, then the emissivity of surface is

In regenerator type heat exchanger, heat transfer takes place by

Absorptivity of a body will be equal to its emissivity

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

Depending on the radiating properties, a body will be black when (where a = absorptivity, p == reflectivity, X = transmissivity.)

Depending on the radiating properties, a body will be opaque when (where a = absorptivity, p = reflectivity, X = transmissivity.)

A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun?

If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of

According to Wien's law, the wavelength corresponding to maximum energy is proportion to

Depending on the radiating properties, body will be transparent when

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