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

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

1 Answer

Answer :

Get doubled.
by

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Description : 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 ... difference (C) Buoyancy of the bubbles produced at active nucleation site (D) None of these

Last Answer : (D) None of these

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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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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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Pick out the wrong statement. (A) In case of heat transfer by purely forced convection, GR /Re 2 ≤ 1 (B) The equivalent diameter of heat transfer for a duct of square cross￾section (having each side as 'x') is equal to 4x (C) Distillation process is not the same as evaporation (D) The effectiveness of nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface

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In the free convection regime of pool boiling, the heat flux is proportional to (A) Δt 1/2 (B) Δt 2 (C) Δt 5/4 (D) Δt

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Last Answer : (C) Δt 5/4

Upto the critical radius of insulation, added insulation, will (A) Increase the heat loss (B) Decrease heat loss and will have no effect beyond that (C) Decrease heat flux (D) Reduce convection heat loss compared to conduction heat less

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A convection process in which an external device, such as a fan, is used to produce the fluid flow.  a. Forced Convection  b. External Convection  c. Placid Convection  d. Thermionic Convection

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_________ is the transition of a given substance from the solid to the gas phase with no intermediate liquid stage.  a. Convection  b. Conduction  c. Radiation  d. Sublimation

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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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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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Last Answer : (B) In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity

In furnaces operating at very high temperature (say) 1250°C, e.g. soaking pit), the maximum heat transfer takes place by (A) Conduction (B) Convection (C) Radiation (D) Cannot be predicted

Description : In furnaces operating at very high temperature (say) 1250°C, e.g. soaking pit), the maximum heat transfer takes place by (A) Conduction (B) Convection (C) Radiation (D) Cannot be predicted

Last Answer : (C) Radiation

Maximum heat transfer in high temperature furnaces is by (A) Conduction (B) Convection (C) Radiation (D) Either (A), (B) or (C); depends on the type of furnace

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Forced recirculation of furnace gases is practised (A) To increase heat transfer by convection (B) To ensure uniform temperature (C) In furnaces, operating below 750°C (D) All (A), (B) and (C)

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Last Answer : (D) All (A), (B) and (C)

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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For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of (A) 1 (B) 1.74 (C) 6.1 (D) 37

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Last Answer : (C) 6.1

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Pick out the wrong statement. (A) In process heat exchangers, saturated steam is preferred over the superheated steam (B) The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1 . If the surface temperature is halved, the maximum in the emissive power would occur at a wavelength of 0.5 λ1 (C) When a vertical plate is heated in infinite air environmental under natural convection conditions, the velocity profile in air, normal to the plate, exhibits a maximum

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Last Answer : (B) The maximum is the emissive power of a surface at a temperature T1 occurs at a wavelength of λ1 . If the surface temperature is halved, the maximum in the emissive power would occur at a wavelength of 0.5 λ1

The heat dissipated by from a surface depends upon its temperature and its characteristics like colour, roughness etc. (a) conduction (b) convection (c) radiation (d) any ofthe above

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A process by which heat is transferred through a material without a bulk movement of the material.  a. Convection  b. Conduction  c. Radiation  d. Emission

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How is heat transferred?  A. By conduction  B. By convection  C. By radiation  D. All of the above

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Which form of heat transfer travels the fastest,convection or conduction?

Description : Which form of heat transfer travels the fastest,convection or conduction?

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Transfer of heat energy from a heater coil to the cooking vessel takes place through the process of- (1) Convection only (2) Conduction and convection only (3) Radiation and convection only (4) Convection, conduction and radiation

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Which of the following are methods of heat transfer? (1) Convection (2) Evaporation (3) Revolution (4) Thermal Expansion

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Description : Heat transfer horizontally within the atmosphere is called – (1) Conduction (2) Convection (3) Absorption (4) Advection

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Nusselt number (for forced convection heat transfer) is a function of the __________ number. (A) Prandtl (B) Reynolds (C) Both (A) & (B) (D) Neither (A) nor (B)

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Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids? (A) Dittus-Boelter equation (B) Sieder-Tate equation (C) Nusselt equation (D) None of these

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The Fourier number (defined as a.t/L 2 ) is used in the analysis of problem involving heat transfer by (A) Forced convection (B) Natural convection(C) Transient conduction(D) Steady state conduction

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Last Answer : (C) Transient conduction

Fourier's law applies to the heat transfer by (A) Convection (B) Radiation (C) Conduction (D) All (A), (B) & (C)

Description : Fourier's law applies to the heat transfer by (A) Convection (B) Radiation (C) Conduction (D) All (A), (B) & (C)

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In which mode of heat transfer, the Biot number is important? (A) Transient heat conduction (B) Natural convection (C) Forced convection (D) Radiation

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Mode of heat transfer involved in the cooling of air cooled internal combustion engine is (A) Conduction(B) Natural convection(C) Forced convection(D) None of these

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Last Answer : (B) Natural convection

In natural convection heat transfer, the correlating parameter is the (A) Graetz number (B) Eckert number (C) Grashoff number (D) Bond number

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In forced convection, the heat transfer depends on(A) Re, Pr (B) Re, Gr (C) Mainly Gr (D) Re only

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When warm and cold liquids are mixed, the heat transfer is mainly by (A) Conduction (B) Convection (C) Radiation (D) Both (A) & (C

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If heat transfer rate varies with the time, it is termed as (A) Forced convection (B) Steady state conduction (C) Monochromatic radiation (D) None of these

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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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