One shot Marathon Series II Heat and Mass transfer for ESE & GATE ME Exams

Question 1

A spherical shell having inside and outside diameters 50cm and 60cm respectively contains a fluid which transfers heat to the wall through conduction at a rate of 100W. If temperature of the wall from inside is 350 K and outside is 300 K then what will be the thermal conductivity of the shell in W/mK

Question 2

The unit of thermal diffusivity is

Question 3

A steel plate of thermal conductivity 50 W/mK and thickness 10 cm passes a heat flux by conduction of25 KW/m². If the temperature of hot surface of the plate is 100°C, then what is the temperature of cooler surface of the plate?

Question 4

If the temperature of a solid surfaces changes from 27⁰ C to 627⁰ C, then its emissive power changes which ratio?

Question 5

A wall of thermal conductivity, k = 0.7 W/m-k transfer 70% of heat loss compare to another wall of k = 0.4 W/m-K, length of 50 mm. The temperature difference is 1.2 times than other wall. Find thickness of 1^st wall (in mm)

Question 6

temperature profile in case of heat transfer through hollow cylinder

Question 7

According to electrical analogy, for a rectangular slab of length L, area A and thermal conductivity K, the resistance can be written as

Question 8

The characteristics satisfied by the lumped or Transient body____.

Question 9

The result of kirchoff’s law for black body is

Question 10

A small tube of 8 mm outside diameter and inside diameter 5 mm is to be laid in atmosphere of 25°C (h_o = 12.5 W/m²-deg) and its inner surface temperature is 50°C. (K)_CABIE = 0.2 W/m-dg. The heat transfer rate in (W/m) is.

Question 11

Conductivity of pure metal is always____.

Question 12

Steady one-dimensional heat flow in a plane wall of thickness ‘L’ with uniform heat generation of

. Right face is maintained at higher temperature T_H as compared to left face (Temperature T_L). Thermal conductivity of plate is constant k. The location of maximum temperature within the plate is:

Question 13

What will be the geometric radius of heat transfer for a hollow sphere of inner radius 5m and outer radius 6 m _________________m

Question 14

Reflectivity is defined as

Question 15

A steel ball of 10 mm diameter at 1000 K is required to be cooled to 350 K by immersing it in a water environment at 300 K. The convective heat transfer coefficient is 1000 W/m²‐K. The thermal conductivity of steel is 40 W/m-K. The time constant for the cooling process 𝜏_th is 16 s. The time required (in s) to reach the final temperature is __________

Question 16

The thermal diffusivity of a cube of side 6cm is 23 × 10^–6 m²/s. what is the Fourier number after 12 sec?

Question 17

Consider two walls, A and B with the same surface areas and the same temperature drops across their thickness. The ratio of thermal conductivities of wall A and B is 4 and the ratio of the wall thickness is 2 respectively. The ratio of heat transfer rates through the walls

is

Question 18

A spherical steel ball of 6 kg is initially at 1600 K and is slowly cooled in a surrounding medium at 200 K and is slowly cooled in a surrounding medium at 200 K with cooling rate of 8 K/s. If the specific heat of body is 256 J/kg-K, then what will be the diameter of ball ____________ (in cm). The heat transfer coefficient of surrounding medium is 220 W/m²K.

Question 19

A hollow cylinder (k = 100 W/mK) of inner radius 4 cm, outer radius 8 cm and length 2m is insulated with 5 cm thick asbestos (k = 0.2 W/mK). The temperature difference between inner most and outmost surface is 600°C . The heat transfer rate is _____________W.

Question 20

Resistance of heat transfer through one dimensional slab

Question 21

A black body is at a temperature of 2500

Maximum emission occurs at a wavelength of ______

Question 22

A furnace wall has thickness of 2 cm and K (thermal conductivity) W/m-K with surface temperature of 600°C and 400°C and the rate of heat conduction us 1000 kW/m². Find the value of thermal conductivity (K) _____________(kW/m-K).

Question 23

A hollow sphere is made up of a metal of thermal conductivity 40 W/mK. Inner radius 0.4 m and outer radius 1m. Difference of temperature between inner and outer wall is 200 °C. Then heat transfer will be ________ kW.

Question 24Multiple Correct Options

Consider the following statement regarding the radiation which of the following are correct.

Question 25Multiple Correct Options

Which of the following statements is/are correct?