Heat Transfer Mechanical previous year questions with answer
Ques 11 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 12 GATE 2017 SET-2
The emissive power of a blackbody is P. If its absolute temperature is doubled, the emissive power becomes
Ques 13 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 14 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 15 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.
Ques 16 GATE 2017 SET-1
Heat is generated uniformly in a long solid cylindrical rod (diameter = 10 mm) at the rate of 4×107 W/m3. The thermal conductivity of the rod material is 25 W/m.K. Under steady state conditions, the temperature difference between the centre and the surface of the rod is ________ °C.
10 is the correct answer.
Ques 17 GATE 2017 SET-1
Two black surfaces, AB and BC, of lengths 5 m and 6 m, respectively, are oriented as shown. Both surfaces extend infinitely into the third dimension. Given that view factor F₁₂ = 0.5, T₁ = 800K, T₂ = 600K, T_surrounding = 300K and Stefan Boltzmann constant, σ = 5.67 × 10⁻⁸ W/(m²K⁴), the heat transfer rate from Surface 2 to the surrounding environment is ________ kW.
3.06 is the correct answer.
Ques 18 GATE 2016 SET-3
Steady one-dimensional heat conduction takes place across the faces 1 and 3 of a composite slab consisting of slabs A and B in perfect contact as shown in the figure, where kA, kB denote the respective thermal conductivities. Using the data as given in the figure, the interface temperature T2 (in °C) is ________.
67.5 is the correct answer.
Ques 19 GATE 2016 SET-3
Grashof number signifies the ratio of
Ques 20 GATE 2016 SET-3
For a heat exchanger, ΔTmax is the maximum temperature difference and ΔTmin is the minimum temperature difference between the two fluids. LMTD is the log mean temperature difference. Cmin and Cmax are the minimum and the maximum heat capacity rates. The maximum possible heat transfer (Qmax) between the two fluids is