GATE Prev Year : Heat Transfer Test-1

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Question 1

Which is correct in respect to turbulence flow?

• ATurbulent flow is less structured and predictable.
• BStructures called eddies dominate the flow.
• CEddies can be any size, ranging from the entire width of the boundary layer to microscopic structures.
• DAll of these

Question 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

• Aa condenser
• Ban evaporator
• Ca counter flow heat exchanger
• Da parallel flow heat exchanger

Question 3

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^-8W/m²K⁴, the net radiation heat exchange rate in kW/m² between the two plates is

• A0.66
• B0.79
• C0.99
• D3.96

Question 4

Water at 80 °C enters a counterflow heat exchanger with a mass flow rate or 0.5 kg/s. Air enters at 30 °Cwith a mass flow rate of 2.09 kg/s. If the effectiveness of the heat exchanger is 0.8, the LMTD (in °C) is

• A40
• B20
• C10
• D5

Question 5

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. 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

• Aa
• Bb
• C2c
• D(b+2c)

Question 6

What happens in thermal boundary layer?

• ATemperature change occurs
• BPressure change occur
• CVolume change occurs
• DHeat change occurs

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