Q. Out of the following four assumptions used in the derivation of the equation for LMTD given by below equation, which one is subject to the largest deviation in practice ?

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Q. For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)

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Q. The interchange factor for radiation heat transfer from surface 'x' to surface 'y' in case of an infinite parallel planes with emis-sivities εx & εy is given by

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Q. What is Nusselt number ?

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Q. The Dietus-Boelter equation for convective heat transfer given by following equation, cannot be used for

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Q. The rate of heat transfer through a pipe wall is given by following equation. For cylinder of very thin wall, q can be approximated by

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Q. Graetz number is given by

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Q. Harmonic mean temperature difference is given by

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Q. Thermal diffusivity is given by

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Q. At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below. The thermal conductivity of material I

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Q. In case of surface condensers, a straight line is obtained on plotting 1/U vs __________ on an ordinary graph paper.

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Q. Fouling factor for a heat exchanger is given by (where, U₁ = heat transfer co-efficient of dirty surface U₂ = heat transfer co-efficient of clean surface)

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Q. For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy

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Q. Following number is called the __________ number.

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Q. What is the logarithmic mean of r1 and r2 ?

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Q. The following equation is the __________ analogy.

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Q. The number given below is termed as the __________ number.

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Q. Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by following equation. This is valid for the value of NRe equal to

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Q. Prandtl number is given by

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Q. For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is

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