Q. The reciprocal of heat transfer co-efficient is _____

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Q. Statement 1: Film-type condensation has a higher heat transfer co-efficient than drop-wise condensation.
Statement 2: Drop-wise condensation is easier to maintain than Film-type condensation

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Q. Statement 1: Drop-wise condensation takes place on a smooth surface.
Statement 2: All the resistance to heat transfer lies in the film formed during Film-type condensation.

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Q. According to Nusselt’s film theory, the film thickness decreases as we move from bottom to top. The heat transfer increases.

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Q. Statement 1: Unsteady state heat transfer equation can be used when there is negligible internal resistance.
Statement 2: Unsteady state heat transfer equation can be used for liquid food items which are well stirred, because, temperature gradient within won’t be there.

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Q. Statement 1: In nusselt’s film theory, velocity of the falling film is not affected by the velocity of the vapors.
Statement 2: LMTD can be used provided the overall heat transfer co-efficient is constant over a large range of temperatures.

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Q. Find heat transfer in an agitated jacketed vessel if Nᵣₑᵢ is 1.5 * 105 and Nₚᵣ is 20.

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Q. Which of the following is NOT a real dimensionless number?

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Q. Statement 1: Nₚᵣ= (Cₚm)/kl
Statement 2: Stanton number is a product of Nᵣₑ and Nₚᵣ.

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Q. Statement 1: G is known as the mass flux and it is the product of density and velocity.
Statement 2: Grashof number is associated with forced convection.

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Q. Фᵥ is generally taken as 1 in food processing as generally very high wall temperatures aren’t reached and hence (µ/µw) * 0.14 is 1 as there isn’t much difference in µ and µw.

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Q. Statement 1: Sieder-Tate and Dittus-boelter equations imply only to laminar flow conditions.
Statement 2: Under laminar conditions, the same equation applies both to Newtonian and Non-Newtonian fluids.

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Q. Dittus-boelter equation is applicable for fluids with phase change.

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Q. Statement 1: Radiation is the transfer of heat by electromagnetic waves.
Statement 2: When heat is radiated from a hot source, the amount of heat received by the body depends on the nature of the body.

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Q. Statement 1: Radiation needs a medium to travel.
Statement 2: Thermal radiation takes place at a certain temperature for every body.

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Q. Statement 1: Radiation is NOT heat.
Statement 2: Maximum value of absorptivity is 1.

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Q. The emission of radiation by any body is independent of the radiation by any body next to it.

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Q. A food industry keeps food cool in a very crude manner, by radiation. It paints its walls white and not black, because of _____

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Q. Which of the following reason does NOT affect radiation between two parallel bodies?

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Q. Freezer is at -18 °C. Will will be Radiative heat transfer if meat is at 298k, its emissivity is 0.82 and average area is 0.045m².
Either use Stefan Boltzmann law or take hᵣ (radiative heat transfer co-efficient) as 0.227.

ε = ( Tₐᵥ/100 )³

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