National Champion Test - GATE 2018 ME : Heat Transfer for ESE & GATE ME Exams

Question 1

A fin will be more effective when Biot number is

Question 2

For a fluid flowing over a flat plate, the Nusselt number at a point 0.5 m from the leading edge is 100. If the thermal conductivity of the fluid is 0.025 W/mK, the coefficient of convective heat transfer is

Question 3

A satellite floats in deep space with very high velocity. It will continuoiusly lose heat by

Question 4

In a balanced counter flow heat exchanger with

, the NTU is equal to 1.0. What is the effectiveness of the heat exchanger?

Question 5

What is the shape factor of a hemisphere body placed on a flat surface with respect to itself?

Question 6

Match List-I (Non-dimensional Number) with List-II (Application) and select the correct answer using the code given below the lists:
List-I
A) Grashoff number
B) Stanton number
C) Sherwood number
D) Fourier number
List-II
1) Mass transfer
2) Unsteady state heat condution
3) Free convection
4) forced convection

Question 7

A plane wall is 20 cm thick with an area of 1 m² and has a thermal conductivity of 0.5 W/m. K. A temperature difference of 100 °C is imposed across it. The heat flow is at:

Question 8

An insulating material with a thermal conductivity, k=0.12 W/mk is used for a pipe carrying steam. The local coefficient of heat transfer (h) to the surrounding is 4 W/m²k. In order to provide effective insulation, the minimum outer diameter of the pipe should be

Question 9

Three fins of equal length and diameter but made of aluminium, brass and cast-iron are heated to 200⁰ C at one end. If the fins dissipate heat to the surrounding air at 25⁰ C the temperature at the free end will be least in case of

Question 10

In a counter flow heat exchanger, hot gases enter at 250 °C and leave at 100 °C. Atmospheric air enters at 50 °C and leaves at 80 °C. The heat capacity of hot fluid is less than cold fluid. The effectiveness of the heat exchanger will be

Question 11

A counter flow shell and tube heat exchanger is used to heat water with hot exhaust gases. The water (c=4180 J/kg K) flows at the rate of 2 Kg/s and the exhaust gases (C = 1000 J/kg K) flow at the rate of 5 kg/s. If the heat transfer surface area is 32 m² and the overall heat transfer coefficient is 200 W/m² K, the NTU of the heat exchanger is

Question 12

What is next radiant interchange per square meter for two very large plates at temperature 800 K and 500 K respectively? Emissivities of hot and cold plates are 0.8 and 0.6 and Stefan-Boltzmann constant is

Question 13

An adiabatic heat exchanger is used to heat cold water at 15ºC entering at a rate of 5 kg/s by hot air at 90ºC entering also at rate of 5 kg/s. If the exit temperature of hot air is 20ºC, the exit temperature of cold water is __________. C_a= 1 and C_w=4.2.

Question 14

Two insulating materials of thermal conductivity K and 2K are available for lagging a pipe carrying a hot fluid,. If the radial thickness of each material is the same.

Question 15

A spherical shaped vessel of 1.4 m outer diameter is 90mm thick. Find the rate of heat leakage, if the temperature difference between the inner and outer surfaces is 220 °C. Thermal conductivity of the material of the sphere is 0.083 W/mK.