Heat Transfer - Study Mode

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[#291] Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?

(A) Dittus-Boeltier equation

(B) Sieder-Tate equation

(C) Nusselt equation

(D) None of these

Correct Answer

(B) Sieder-Tate equation

[#292] Which of the following situations can be approximated to a steady state heat transfer system?

(A) A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C

(B) 10 kg of dry saturated steam at 8 kgf/cm 2 flowing through a short length of stainless-steel pipe exposed to atmospheric air at 35°C

(C) Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C

(D) A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C

Correct Answer

(B) 10 kg of dry saturated steam at 8 kgf/cm 2 flowing through a short length of stainless-steel pipe exposed to atmospheric air at 35°C

[#293] While the total emissivity of a perfect black body is unity, the same for a real body is

(A) 0

(B) 1

(C) > 1

(D) Between 0 and 1

Correct Answer

(D) Between 0 and 1

[#294] Pick out the wrong statement:

(A) The capacity of an evaporator is reduced by the boiling point elevation

(B) Corrosive liquid is normally passed through the tubes in a shell and tube heat exchanger

(C) Steam jet ejector is used for vapor compression in a thermal recompression evaporator

(D) Heat sensitive materials should be concentrated in high pressure evaporators

(E) With change in temperature, the radiant energy emitted by a black body remains unchanged

(F) Absorptivity of a body approaches unity in case of diffuse reflection

(G) Absorptivity of a perfectly black body is unity

(H) Value of Stefan-Boltzman constant is 4.876 × 10 -8 kcal/m 2 .hr.°K 4

Correct Answer

(D) Heat sensitive materials should be concentrated in high pressure evaporators
(E) With change in temperature, the radiant energy emitted by a black body remains unchanged

[#295] The Graetz number is concerned with the

(A) Mass transfer between a gas and a liquid

(B) Absorption with chemical reaction

(C) Heat transfer in turbulent flow

(D) Heat transfer in laminar flow

Correct Answer

(D) Heat transfer in laminar flow