Heat Transfer Mechanical previous year questions with answer
Ques 41 GATE 2014 SET-2
A hemispherical furnace of 1 m radius has the inner surface (emissivity, ε = 1) of its roof maintained at 800 K, while its floor (ε = 0.5) is kept at 600 K. Stefan-Boltzmann constant is 5.668 × 10−8 W/m2·K4. The net radiative heat transfer (in kW) from the roof to the floor is _______
24.6 is the correct answer.
Ques 42 GATE 2014 SET-2
A material P of thickness 1 mm is sandwiched between two steel slabs. A heat flux of 10 kW/m2 is supplied to one of the steel slabs. The boundary temperatures of the slabs are 100°C and 60°C. Thermal conductivity of steel is 10 W/m·K. Considering 1-D steady state heat conduction, the thermal conductivity (k, in W/m·K) of material P is _______
0.1 is the correct answer.
Ques 43 GATE 2014 SET-2
In a concentric counter flow heat exchanger, water flows through the inner tube at 25°C and leaves at 42°C. The engine oil enters at 100°C and flows in the annular flow passage. The exit temperature of the engine oil is 50°C. Mass flow rate of water and the engine oil are 1.5 kg/s and 1 kg/s, respectively. The specific heat of water and oil are 4178 J/kg·K and 2130 J/kg·K, respectively. The effectiveness of this heat exchanger is _______
0.66 is the correct answer.
Ques 44 GATE 2014 Set-1
Biot number signifies the ratio of
Ques 45 GATE 2014 Set-1
Consider a two-dimensional laminar flow over a long cylinder as shown in the figure below.
Ques 46 GATE 2014 Set-1
Consider one dimensional steady state heat conduction across a wall (as shown in figure below) of thickness 30 mm and thermal conductivity 15 W/m.K. At x = 0, a constant heat flux, q" = 1×105 W/m2 is applied. On the other side of the wall, heat is removed from the wall by convection with a fluid at 25°C and heat transfer coefficient of 250 W/m2.K. The temperature (in °C), at x = 0 is _______
620 to 630 is the correct answer.
Ques 47 GATE 2014 Set-1
The non-dimensional fluid temperature profile near the surface of a convectively cooled flat plate is given by 
where y is measured perpendicular to the plate, L is the plate length, and a, b and c are arbitrary constants. TW and T∞ are wall and ambient temperatures, respectively. If the thermal conductivity of the fluid is k and the wall heat flux is q" , the Nusselt number 
is equal to
Ques 48 GATE 2013 SET-4
Consider one-dimensional steady state heat conduction along x-axis (0 ≤ x ≤ L), through a plane wall with the boundary surfaces (x=0 and x=L) maintained at temperatures of 0°C and 100°C. Heat is generated uniformly throughout the wall. Choose the CORRECT statement.
Ques 49 GATE 2013 SET-4
Consider one-dimensional steady state heat conduction, without heat generation, in a plane wall; with boundary conditions as shown in the figure. The conductivity of the wall is given by k = k0 + bT; where k0 and b are positive constants, and T is temperature. As x increases, the temperature gradient (dT/dx) will
Ques 50 GATE 2013 SET-4
Two large diffuse gray parallel plates, separated by a small distance, have surface temperatures of 400 K and 300 K. If the emissivities of the surfaces are 0.8 and the Stefan-Boltzmann constant is 5.67×10-8 W/m2K4, the net radiation heat exchange rate in kW/m2 between the two plates is