Q. Natural convection is characterised by

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Q. Nusselt number for full developed, laminar, constant property flow in a pipe at uniform heat flux is

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Q. Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is

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Q. The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe )

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Q. If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.

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Q. In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred

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Q. __________ equation relates the thermal conductivity of a solid to its temperature.

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Q. For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature)

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Q. Pick out the wrong statement.

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Q. In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid.

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Q. A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes.

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Q. In forced convection, the Nusselt number is a function of

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Q. At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical ?

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Q. A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because

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Q. Pick out the wrong statement.

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Q. When warm and cold liquids are mixed, the heat transfer is mainly by

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Q. A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?

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Q. Vent pipes are provided in a condenser to

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Q. Heat transfer by natural convection is enhanced in system with

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Q. Grashoff number, which is defined as g . β(Ts - T∞) ρ². L³/μ², is proportional to the ratio of buoyancy force to __________ force.

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