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

Question 1

Upto the critical radius of insulation

Question 2

The ‘NTU’ (Number of transfer Units) in a heat exchanger is given by which one of the following?

where, U = Overall heat transfer coefficient
C = Heat capacity
E = Effectiveness
A = Heat exchange area

Question 3

In case of liquids, what is the binary diffusion coefficient proportional to?

Question 4

The Reynolds-Colburn analogy, which is used to determine heat transfer coefficient from the measurement of frictional drag, is applicable to

Question 5

Fins are used to increase the heat transfer from surface by _____.

Question 6

The equation of effectiveness

for a heat exchanger is valid in the case of

Question 7

Network analysis refers to:

Question 8

What is the ratio of thermal conductivity to electrical conductivity equal to?

Question 9

An unconstrained thin circular disc has a concentric hole in it. On heating the diameter of the hole will

Question 10

A solid sphere 1 of radius ‘r’ is placed inside a hollow, closed hemispherical surface 2 of radius ‘4r’. The shape factor F_2-1 is

Question 11

The logarithmic mean temperature difference (LMTD) of a counter flow heat exchanger is 20 °C. The cold fluid enters at 20 °C and the hot fluid enters at 100 °C. Mass flow rate of the cold fluid is twice that of the hot fluid. Specific heat at constant pressure of the hot fluid is twice that of the cold fluid. The exit temperature of the cold fluid

Question 12

The temperature distribution within the thermal boundary layer over a heated isothermal flat plate is given by

,
where T_w and T_∞ are the temperatures of plate and free stream respectively, and y is the normal distance measured from the plate. The local Nusselt number based on the thermal boundary layer thickness δ_t is given by

Question 13

A hollow enclosure is formed between two infinitely long concentric cylinders of radii 1 m and 2 m, respectively. Radiative heat exchange takes place between the inner surface of the larger cylinder (surface-2) and the outer surface of the smaller cylinder (surface-1). The radiating surfaces are diffuse and the medium in the enclosure is non-participating. The fraction of the thermal radiation leaving the larger surface and striking itself is

Question 14

The effectiveness of a fin will be maximum in an

Question 15

Two infinite parallel plates are placed at a certain distance apart. An infinite radiation shield is inserted between the plates without touching any of them to reduce heat exchange between the plates. Assume that the emissivities of plates and radiation shield are equal. The ratio of the net heat exchange between the plates with and without the shield is

Question 16

Water flows through a tube of diameter 25 mm at an average velocity of 1.0 m/s. The properties of water are ρ = 1000 kg/m³, μ = 7.25 × 10^-4 N.s/m², k = 0.625 W/m.K, Pr = 4.85 using Nu = 0.023Re^0.8Pr^0.4, the convective heat transfer coefficient (in W/m².K) is ________.

Question 17

A plane wall has a thermal conductivity of 1.15 W/m.K. If the inner surface is at 1100 °C and the outer surface is at 350 °C, then the design thickness (in meter) of the wall to maintain a steady heat flux of 2500 W/m² should be______

Question 18

Match Group A with Group B:

Question 19

Water

at 80 °C enters a counterflow heat exchanger with a mass flow rate or 0.5 kg/s. Air

enters at 30 °Cwith a mass flow rate of 2.09 kg/s. If the effectiveness of the heat exchanger is 0.8, the LMTD (in °C) is

Question 20

A small copper ball of 5 mm diameter at 500 K is dropped into an oil bath whose temperature is 300 K. the thermal conductivity of copper is 400 W/m.K, its density 9000 kg/m³ and its specific heat 385 J/kg.K. if the heat transfer coefficient is 250 W/ m².K and lumped analysis is assumed to be valid, the rate of fall of the temperature of the ball at the beginning of cooling will be, in K/s,

Question 21

Heat flows through a composite slab, as shown below. The depth of the slab is 1 m. the k values are in W/m K. the overall thermal resistance in K/W is
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Question 22

A cylindrical uranium fuel rod of radius 5 mm in a nuclear reactor is generating heat at the rate of 4 × 10⁷ W/m³ the rod is cooled by a liquid (convective heat transfer coefficient 1000 W/m²-K) at 25 °C. At steady state, the surface temperature (in K) of the rod is

Question 23

The transition Reynolds number for flow over a flat is 5 X

. What is the distance from the leading edge at which transition will occur for flow of water with a uniform velocity of 1m/s? (For water, the kinematic viscosity, v = 0.858 X

)

Question 24

A fluid (Prandtl number, Pr = 1) at 500 K flows over a flat plate of 1.5 m length, maintained at 300 K. The velocity of the fluid is 10 m/s. Assuming kinematic viscosity, ν = 30 × 10 − 6 m²/s, the thermal boundary layer thickness (in mm) at 0.5 m from the leading edge is __________

Question 25

An infinitely long furnace of 0.5 m × 0. 4 m cross-section is shown in the figure below. Consider all surfaces of the furnace to be black. The top and bottom walls are maintained at temperature T₁ = T₃ = 927℃while the side walls are at temperature T₂ = T₄ = 527℃. The view factor, F1-2 is 0.26. The net radiation heat loss or gain on side 1 is_________ W/m. Stefan-Boltzmann constant = 5.67 × 10⁻⁸ W/m²‐K⁴