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GATE ME 2019 National Champion Quiz: Heat Transfer (App update required to attempt this test)

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Question 1

Heat is conducted through a 10 cm thick wall at the rate of 60 W/m² when the temperature difference across the wall is 20 °C what is the thermal conductivity of the wall?

Question 2

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 3

The shields used between two surface is usually reduce the heat transfer by radiation between the two surfaces by

Question 4

A 4 mm diameter and 10 cm long aluminum fin (Thermal conductivity, k = 237 W/m-K) is attached to a surface. If the heat transfer coefficient is 12 W/m2-K, what is the percentage error in the calculation of rate of heat transfer from the fin when the infinitely long fin assumption is used instead of the adiabatic fin tip assumption?

Question 5

Find the radiation heat exchange between two large parallel steel plates of emissivities 0.7 and 0.5 held at temperatures of 1000 K and 500 K respectively, if a thin copper plate of emissivity 0.1 is introduced as a radiation shield between the two plates is?

Question 6

Consider a long cylindrical tube of inner and outer radii, r_i and r₀, respectively, length, L and thermal conductivity, k. Its inner and outer surfaces are maintained at T_i and T₀, respectively T_i > T₀. Assuming one-dimensional steady state heat conduction in the radial direction, the thermal resistance in the wall of the tube is

Question 7

A stainless steel tube of inner diameter 0.04 m and outer diameter 0.12 m is insulated with 0.02 m thick material asbestos. If the temperature difference between innermost and outermost surface is 600 °C, find out the heat transfer rate per unit length. (Take K_a = 0.4 W/mK and K_s = 20 W/mK.)

Question 8

A coolant fluid at 30 °C flows over a heated flat plate maintained at a constant temperature of 110 °C. The boundary layer temperature distribution at a given location on the plate may be approximated as

where y (in m) is the distance normal to the plate and T is in °C. If thermal conductivity of the fluid is 1.0 W/m-K, the local convective heat transfer coefficient at that location will be ____________ W/m²-K.

Question 9

A metal plate 0.609 m high forms the vertical wall of an oven and is at a temperature of 161⁰C. Within the oven air is at a temperature of 93⁰C. Assuming the natural convection conditions hold near the plate.
The properties of air at 400 K are
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The Rayleigh number will be

Question 10

In a heat exchanger, the hot liquid enters with a temperature of 200 °C and leaves at 180 °C. The cooling fluid enters at 50 °C and leaves at 130 °C. The capacity ratio of the heat exchanger is __________.

Question 11

The inlet temperature of a counter flow heat exchanger for hot and cold fluid is 170

and 30

. The ratio of capacity rate for hot and cold fluid is 1. Find the LMTD (degree celcius) of the heat exchanger. Take effectiveness ε=0.7

Question 12

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

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ESE & GATE ME Heat Transfer

Oct 16ESE & GATE ME