Heat Transfer Mechanical previous year questions with answer
Ques 41 GATE 2015 SET-1
A 10 mm diameter electrical conductor is covered by an insulation of 2 mm thickness. The conductivity of the insulation is 0.08 W/m-K and the convection coefficient at the insulation surface is 10 W/m2-K. Addition of further insulation of the same material will
Ques 42 GATE 2014 SET-3
Consider a long cylindrical tube of inner and outer radii ri and ro, respectively, and length L and thermal conductivity k. Its inner and outer surfaces are maintained at Ti and To respectively (Ti > To). Assuming one-dimensional steady-state heat conduction in the radial direction, the thermal resistance in the wall of the tube is
Ques 43 GATE 2014 SET-3
Consider a gas turbine blade of 1 mm thickness, made of super alloy with k = 20 W/m·K. The blade is attached to a base and exposed to hot gases on the other side. The convective heat transfer coefficient between the blade and the gas is 1500 W/m2·K. If the temperature of the gas is 1200°C and that of the base is 900°C, the temperature (in °C) of the exposed surface of the blade is _______
916.7 is the correct answer.
Ques 44 GATE 2014 SET-2
For laminar forced convection over a flat plate, if the free stream velocity increases by a factor of 2, the average heat transfer coefficient
Ques 45 GATE 2014 SET-2
In a heat exchanger, it is observed that ΔT1 = ΔT2, where ΔT1 is the temperature difference between the two single phase fluid streams at one end and ΔT2 is the temperature difference at the other end. This heat exchanger is
Ques 46 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 47 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 48 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 49 GATE 2014 Set-1
Biot number signifies the ratio of
Ques 50 GATE 2014 Set-1
Consider a two-dimensional laminar flow over a long cylinder as shown in the figure below.
