Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the (A) Existence of thermal boundary layer (B) Temperature gradient produced due to density difference (C) Buoyancy of the bubbles produced at active nucleation site (D) None of these

Fluid motion in the natural convection heat transfer between a solid
surface and a fluid in contact with it, results from the
(A) Existence of thermal boundary layer
(B) Temperature gradient produced due to density difference
(C) Buoyancy of the bubbles produced at active nucleation site
(D) None of these
by

1 Answer

Answer :

(D) None of these
by

Related questions

When the ratio of the Grashoff number and to the square of Reynolds number is one, the dominant mechanism of heat transfer is: (A) Free convection (B) Entry length problem in laminar forced conduction (developing thermal boundary layer) (C) Mixed convection (both free and forced) (D) Forced convection

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Last Answer : (C) Mixed convection (both free and forced)

Heat transfer occurs by natural convection because change in temperature causes difference in (A) Viscosity (B) Density (C) Thermal conductivity (D) Heat capacity

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Last Answer : (B) Density

Existence of boundary layer in fluid flow is because of the (A) Surface tension (B) Fluid density (C) Fluid viscosity (D) Gravity forces

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Last Answer : (C) Fluid viscosity

reduction in thermal resistance during heat transfer does not occur in the (A) Convection heat transfer by stirring the fluid and cleaning the heating surface (B) Conduction heat transfer by reduction in the material thickness and increase in the thermal conductivity (C) Radiation heat transfer by increasing the temperature and reducing the emissivity (D) None of these

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Last Answer : Option C

In convection heat transfer, if heat flux intensity is doubled then temperature difference between solid surface and fluid will ?

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Last Answer : Get doubled.

What refers to the transfer of energy between a solid surface and the adjacent fluid that is in motion?  A. Conduction  B. Convection  C. Radiation  D. Electrification

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At the point of boundary layer separation in fluid flow, the (A) Shear stress is maximum (B) Velocity gradient is flat (C) Density variation is maximum (D) Shear stress is zero

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Last Answer : (D) The Colburn jH factor for heat transfer is given by Nst Npr

Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called (A) Radiation (B) Natural convection (C) Forced convection (D) Conduction

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Heat transfer by natural convection is enhanced in system with (A) High viscosity (B) High co-efficient of thermal expansio

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Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer. (A) Grashoff (B) Biot (C) Stanton

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Momentum transfer in laminar flow of fluids results due to the (A) Viscosity (B) Density (C) Velocity gradient (D) None of these

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Pick out the correct statement. (A) 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity (C) In unsteady state heat conduction, heat flows in the direction of temperature rise (D) In heat transfer by forced convection, Grashoff number is very important

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In a heat exchanger, floating head is provided to (A) Facilitate cleaning of the exchanger (B) Increase the heat transfer area (C) Relieve stresses caused by thermal expansion (D) Increase log mean temperature gradient

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Which of the following must be followed by the flow of a fluid (real or ideal)? (I) Newton's law of viscosity. (II) Newton's second law of motion. (III) The continuity equation. (IV) Velocity of boundary layer must be zero relative to boundary. (V) Fluid cannot penetrate a boundary. (A) I, II, III (B) II, III, V (C) I, II, V (D) II, IV, V

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The effect of solid boundary on the fluid flow is confined to the boundary layer, except for fluids (A) Having high viscosities (B) Moving at low velocities (C) Both (A) & (B) (D) Neither (A) nor (B)

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The boundary layer is that part of a moving fluid, in which the fluid velocity is (A) Affected by the fluid flow pressure (B) Constant(C) Affected by the presence of a solid boundary(D) All (A), (B) and (C)

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The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as (A) (ΔT) 1/4 (B) (ΔT) 1/2 (C) (ΔT) 5/4 (D) (ΔT) 3/4

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In a furnace with heating element temperature at 1700°C, the dominant mechanism of heat transfer will be (A) Conduction (B) Radiation (C) Natural convection (D) Forced convection

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The surface of water in a pond remains cool even on a hot day because 1. water evaporates at the surface and evaporation causes cooling 2. the heat absorbed at the surface is transmitted downwards 3. Water in contact with the bottom of the pond becomes cool and rises to the surface due to convection Which of the above statements is/are correct? (a) 1 only (b) 3 only (c) 1 and 3 (d) 1, 2 and 3

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Rate of heat transfer by vaporisation from pools of water is affected by the (A) Nature of heating surface and distribution of bubbles (B) Surface tension of water (C) Viscosity of water (D) All (A), (B) and (C)

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Which of the following represents the perpetual motion of the first kind  (a) engine with 100% thermal efficiency  (b) a fully reversible engine  (c) transfer of heat energy from low temperature source to high temperature source  (d) a machine that continuously creates its own energy  (e) production of energy by temperature differential in sea water at different levels.

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