Heat Transfer Mechanical previous year questions with answer
Ques 1 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 2 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 3 GATE 2022 SET-2
Which of the following non-dimensional terms is an estimate of Nusselt number?
Ques 4 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=(2𝑥)î +(𝑦+3𝑡)ĵ , given and the temperature field is T=2𝑥2 +𝑥𝑦+4𝑡, 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 5 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.
Ques 6 GATE 2022 SET-1
Consider a rod of uniform thermal conductivity whose one end (x=0) is insulated and the other end (x=L) is exposed to air at T∞ with heat transfer coefficient h. The rate of internal heat generation per unit volume is given as
Ques 7 GATE 2022 SET-1
Consider a one-dimensional steady heat conduction process through a solid slab of thickness 0.1 m. The higher temperature side A has a surface temperature of 80°C, and the heat transfer rate per unit area to the low temperature side B is 4.5 kW/m². The thermal conductivity of the slab is 15 W/m·K. The rate of entropy generation per unit area during the heat transfer process is ________ W/m²·K (round off to 2 decimal places).
0.09 is the correct answer.
Ques 8 GATE 2022 SET-1
Consider a solid slab (thermal conductivity, k = 10 W·m⁻¹·K⁻¹) with thickness 0.2 m and of infinite extent in the other two directions as shown in the figure. Surface 2, at 300 K, is exposed to a fluid flow at free stream temperature (T∞) of 293 K, with a convective heat transfer coefficient (h) of 100 W·m⁻²·K⁻¹. Surface 2 exchanges heat by radiation with very large surroundings at 0 K. Radiative heat transfer inside the solid slab is neglected. The Stefan-Boltzmann constant is 5.67×10-8 W·m⁻²·K⁻¹. The temperature T1 of Surface 1 of the slab, under steady-state conditions, is _________ K (round off to the nearest integer).
330 is the correct answer.
Ques 9 GATE 2022 SET-1
During open-heart surgery, a patient’s blood is cooled down to 25 °C from 37 °C
using a concentric tube counter-flow heat exchanger. Water enters the heat
exchanger at 4 °C and leaves at 18 °C. Blood flow rate during the surgery is
5 L/minute.
Use the following fluid properties:
0.80 is the correct answer.
Ques 10 Gate 2021 Set-2
In forced convective heat transfer, Stanton number (St), Nusselt number (Nu), Reynolds number (Re) and Prandtl number (Pr) are related as