Q. A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is

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Q. For a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

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Q. The main purpose of providing fins on heat transfer surface is to increase the

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Q. A BTU/hr.ft.² °F is equal to

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Q. Which of the following has the lowest Prandtl number ?

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Q. Choose the most important factor on which the heat conducted through a wall in a unit time will depend on ?

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Q. Which of the following has the minimum thermal conductivity ?

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Q. In a heat exchanger, one transfer unit means

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Q. For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then

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Q. Pick out the wrong statement:

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Q. The advantage of backward feed multiple effect evaporators over forward feed units is that

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Q. Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface ?

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Q. Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger ?

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Q. Thermal conductivities of most of the liquids __________ with rise in temperature.

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Q. A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

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Q. Intermittant tube cleaning is possible to be done in case of a __________ evaporator.

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Q. Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is

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Q. Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for

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Q. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about

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Q. For concentrating an aqueous solution of a material like anhydrous Na₂SO₄, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator.

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