Heat Transfer Mechanical previous year questions with answer
Ques 11 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 12 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 13 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 14 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 15 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
Ques 16 GATE 2017 SET-2
The heat loss from a fin is 6 W. The effectiveness and efficiency of the fin are 3 and 0.75, respectively. The heat loss (in W) from the fin, keeping the entire fin surface at base temperature, is ________.
8 is the correct answer.
Ques 17 GATE 2017 SET-2
The emissive power of a blackbody is P. If its absolute temperature is doubled, the emissive power becomes
Ques 18 GATE 2017 SET-2
In a counter-flow heat exchanger, water is heated at the rate of 1.5 kg/s from 40°C to 80°C by an oil entering at 120°C and leaving at 60°C. The specific heats of water and oil are 4.2 kJ/kg.K and 2 kJ/kg.K respectively. The overall heat transfer coefficient is 400 W/m2.K. The required heat transfer surface area (in m2) is
Ques 19 GATE 2017 SET-2
A metal ball of diameter 60 mm is initially at 220°C. The ball is suddenly cooled by an air jet of 20°C. The heat transfer coefficient is 200 W/m2.K. The specific heat, thermal conductivity and density of the metal ball are 400 J/kg.K, 400 W/m.K and 9000 kg/m3, respectively. The ball temperature (in °C) after 90 seconds will be approximately
Ques 20 GATE 2017 SET-1
Saturated steam at 100°C condenses on the outside of a tube. Cold fluid enters the tube at 20°C and exits at 50°C. The value of the Log Mean Temperature Difference (LMTD) is ________ °C.
63.8 is the correct answer.