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GATE 2022 ME: Heat-Transfer Revision Quiz

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Question 1

Lumped Heat-transfer analysis of a solid object suddenly exposed to a fluid medium at a different temperature is valid when _________.

Question 2

Which is true for sequence of the thermal conductivity_____.?

Question 3

A hollow cylinder has length L, inner radius r1, outer radius r2, and thermal conductivity k. The thermal resistance of the cylinder for radial conduction is

Question 4

Heat is loss from a 200 mm diameter steam pipe placed horizontally in ambient at 30 °C if the nusselt number of air is 50 and thermal conductivity of air is 0.03 W/mk, then the heat transfer coefficient will be

Question 5

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 6

A wall of 0.5 m thickness is to be constructed from a material which has an average thermal conductivity of 1.4 W/m-K. The wall is to be insulated with a material having an average thermal conductivity of 0.35 W/m-K so that the heat loss per square metre will not exceed 1450 W. Assuming that the inner and outer surface temperature are 1200 °C and 15 °C respectively. The thickness of insulation required is ____ metre.

Question 7

A cylindrical steel rod, 0.01 m in diameter and 0.2 m in length is first heated to 750 oC and then immersed in a water bath at 100 oC. The heat transfer coefficient is 250 W/m2-K. The density, specific heat and thermal conductivity of steel are ρ = 7801 kg/m3, c = 473 J/kg-K, and k =43 W/m-K, respectively. The time required for the rod to reach 300 oC is _____ seconds.

Question 8

Match List-I (process) with List-II (predominant parameter associated with the process) and select the correct answer using the codes given below:
(A). Mass transfer
(B). Forced convection
(C). Free convection
(D). Transient conduction
(1). Reynolds number
(2). Sherwood number
(3). Mach number
(4). Biot number
(5). Grashoff number

Question 9

A plate having 10 cm2 area each side is hanging in the middle of a room of 100 m2 total surface area. The plate temperature and emissivity are respectively 800 K and 0.6. the temperature and emissivity values for the surfaces of the room are 300K and 0.3 respectively. Boltzmann’s constant σ = 5.67 × 10–8 W/m2K4. The total heat loss from the two surfaces of the plate is

Question 10

A smaller sphere (1) of radius 50 mm is inside a larger sphere (2) of radius 100 mm. What will be the value of the radiation shape factor F22:

Question 11

A steel ball l of radius 30 mm is initially in thermal equilibrium at 1000 ° C in furnace. It is then suddenly removed and cooled in ambient air at 30 ° C with convection heat transfer coefficient h = 20 W/m2K. find the time required in seconds to cool the steel ball in air from 1000 ° C to 450 ° C, (Take thermo physical properties of steel: density ρ = 7600 kg/m3, Conductivity k = 40 W/mK, specific heat Cp = 500 J/kg K.)

Question 12

Two large parallel plates having temperatures T1 = 1500K and T2 = 500K are kept in such a way that radiation leaving from each surface is completely reached the 2nd surface. Emissivity values for plates are 0.5 and 0.25 respectively. Then heat transfer between the plates __________ (in kW/m2).

Question 13

A pipe of 25 mm outer diameter carries steam. The heat transfer coefficient between the cylinder and surroundings is 5W/m2K. It is proposed to reduce the heat loss from the pipe by adding insulation having a thermal conductivity of 0.05 W/mK. Which one of the following statements is TRUE?

Question 14

Heat is generated uniformly in a long solid cylindrical rod (diameter = 10mm) at the rate of . The thermal conductivity of the rod material is 25W/m.K. Under steady state conditions, the temperature difference between the centre and the surface of the rod is _________ °C.

Question 15

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 __________
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