Heat Transfer Mechanical previous year questions with answer
Ques 1 GATE 2026
A quiescent fluid at temperature T3 is confined between two vertical parallel plates. While plate 1 is kept at temperature T1 and plate 2 is maintained at temperature T2, a velocity profile between the plates, as shown in the figure below, is generated due to heat transfer. Which one of the following options shows the correct relations among T1, T2, and T3?
Ques 2 GATE 2026
A sphere of radius 5 mm is initially in equilibrium at 400℃ in a furnace. It is suddenly removed from the furnace and dipped in a well-stirred water bath at 20℃, with a convection heat transfer coefficient of 500 W/(m2K). For the given range of temperatures, the thermophysical properties of the material of the sphere are: density ρ = 3000 kg/m3, thermal conductivity k = 10 W/(mK), and specific heat c = 1000 J/(kgK). Neglecting radiation heat transfer, the time required for the centre of the sphere to cool from 400℃ to 50℃ is ________ seconds (rounded off to 2 decimal places).
35.24 is the correct answer.
Ques 3 GATE 2026
A very long fin of a uniform square cross-section is replaced by another very long fin of a uniform circular cross-section of the same material. Assume uniform and identical heat transfer coefficient for both the fins. If the diameter of the circular fin is equal to the side length of the square fin, then the ratio of heat transfer rates before and after the replacement is
Ques 4 GATE 2026
Two rectangular surfaces both having 1 m2 area are placed perpendicular to each other with a common edge. One surface is hot, having a temperature of 1000 K and emissivity of 0.4, while the other is insulated and in radiant balance with a large surrounding room at 300 K. If the fraction of radiation leaving the hot surface which reaches the cold surface is 0.2, then the equivalent overall resistance for the radiation heat loss from the hot surface is _______ m−2 (rounded off to 2 decimal places).
2.94 is the correct answer.
Ques 5 GATE 2026
Convective heat transfer coefficients for Fluid 1 and Fluid 2 in a heat exchanger, as shown in the figure below, are 50 W/(m2K) and 80 W/(m2K), respectively. The inner tube is made of a material which has a thermal conductivity 386 W/(mK) for the given range of temperatures in the heat exchanger. The length of the heat exchanging surface, the inside radius of the inner tube, and thickness of the inner tube are 1 m, 10 mm, and 1 mm, respectively. Considering no heat exchange between the outer tube and the surrounding, the heat transfer rate for the heat exchanger is ________ W (rounded off to 1 decimal place).
722.6 is the correct answer.
Ques 6 GATE 2025
Consider a cylindrical furnace of 5 m diameter and 5 m length with bottom, top and curved surfaces maintained at uniform temperatures of 800 K, 1500 K and 500 K, respectively. The view factor between the bottom and top surfaces, F12 is 0.2. The magnitude of net radiation heat transfer rate between the bottom surface and the curved surface is ______ kW (rounded off to 1 decimal place).
All surfaces of the furnace can be assumed as black.
The Stefan-Boltzmann constant, σ=5.67×10-8 W m-2K-4.
Ques 7 GATE 2025
Water enters a tube of diameter, D = 60 mm with mass flow rate of 0.01 kg s-1 as shown in the figure below. The inlet mean temperature is Tm,i=293 K and the uniform heat flux at the surface of the tube is 2000 W m-2. For the exit mean temperature of Tm,o=353 K, the length of the tube, L is ______ m (rounded off to 1 decimal place).
Use the specific heat of water as 4181 Jkg-1 K-1.
Ques 8 GATE 2022 SET-2
Which of the following non-dimensional terms is an estimate of Nusselt number?
Ques 9 GATE 2022 SET-1
A tiny temperature probe is fully immersed in a flowing fluid and is moving with zero relative velocity with respect to the fluid. The velocity field in the fluid is v⃗=(2π₯)iΜ +(π¦+3π‘)jΜ , given and the temperature field is T=2π₯2 +π₯π¦+4π‘, where x and y are the spatial coordinates, and t is the time. The time rate of change of temperature recorded by the probe at (x=1, y=1, t=1) is?
Ques 10 GATE 2022 SET-1
A flat plate made of cast iron is exposed to a solar flux of 600 W/m2 at an ambient temperature of 25 °C. Assume that the entire solar flux is absorbed by the plate.
Cast iron has a low temperature absorptivity of 0.21. Use Stefan-Boltzmann constant = 5.669 × 10-8 W/m2-K4. Neglect all other modes of heat transfer except radiation.
Under the aforementioned conditions, the radiation equilibrium temperature of the plate is __________ °C (round off to the nearest integer).
75 is the correct answer.