How convective heat transfer is effected and on what factors it depends ?

How convective heat transfer is effected and on what factors it depends ?
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1 Answer

Answer :

Convective heat transfer is effected between a solid and fluid by a combination of molecular conduction
within the fluid in combination with energy transport resulting from the motion of fluid particles. It
depends on boundary layer configuration, fluid properties and temperature difference.
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Related questions

Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Description : Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. (A) Laminar (B) Transition (C) Both 'a' & 'b' (D) Highly turbulent

Last Answer : (D) Highly turbulent

Bulk of the convective heat transfer resistance from a hot tube surfaceto the fluid flowing in it, is(A) In the central core of the fluid(B) Uniformly distributed throughout the fluid(C) Mainly confined to a thin film of fluid near the surface(D) None of these

Description : Bulk of the convective heat transfer resistance from a hot tube surfaceto the fluid flowing in it, is (A) In the central core of the fluid (B) Uniformly distributed throughout the fluid (C) Mainly confined to a thin film of fluid near the surface (D) None of these

Last Answer : (C) Mainly confined to a thin film of fluid near the surface

A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Description : A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m2 .K. The Biot number is (A) 5.6 (B) 0.025 (C) 3.5 (D) 0.0035

Last Answer : (B) 0.025

Convective heat transfer, in which heat is transferred by movement of warmed matter is described by (A) Fourier's law (B) Newton's law of cooling (C) Fick's law (D) None of these

Description : Convective heat transfer, in which heat is transferred by movement of warmed matter is described by (A) Fourier's law (B) Newton's law of cooling (C) Fick's law (D) None of these

Last Answer : (B) Newton's law of cooling

The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re) 0.8 (Pr) 0.4 ] cannot be used for (A) Low Reynold's number (B) Very low Grashoff number (C) Molten metals (D) All (A), (B) and (C)

Description : The Dittus-Boelter equation for convective heat transfer [(i.e. h = 0.023 (K/D) (Re) 0.8 (Pr) 0.4 ] cannot be used for (A) Low Reynold's number (B) Very low Grashoff number (C) Molten metals (D) All (A), (B) and (C)

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

Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger? (A) Tube side pressure drop and the heat transfer rate (B) Convective heat transfer co-efficient (C) Effective tube surface area for convective heat transfer (D) All (A) (B) and (C)

Description : Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger? (A) Tube side pressure drop and the heat transfer rate (B) Convective heat transfer co-efficient (C) Effective tube surface area for convective heat transfer (D) All (A) (B) and (C)

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

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 (A) 1.26 h1(B) 0.794 h1(C) 0.574 h1(D) 1.741 h1

Description : 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 (A) 1.26 h1 (B) 0.794 h1 (C) 0.574 h1 (D) 1.741 h1

Last Answer : (B) 0.794 h1

What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Description : What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40

Last Answer : (A) 2

A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

Description : A thin, flat & square plate measuring 2 m 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will ... heat transfer co-efficient is __________ W/m2 °C. (A) 50 (B) 100 (C) 150 (D) 200

Last Answer : (B) 100

Entropy change depends on  (a) heat transfer  (b) mass transfer  (c) change of temperature  (d) thermodynamic state  (e) change of pressure and volume.

Description : Entropy change depends on  (a) heat transfer  (b) mass transfer  (c) change of temperature  (d) thermodynamic state  (e) change of pressure and volume.

Last Answer : Answer : a

The hyperboloid shape also aids in accelerating the upward convective air flow, improving ________ efficiency. • Performance • Cooling • Heating • All of the above

Description : The hyperboloid shape also aids in accelerating the upward convective air flow, improving ________ efficiency. • Performance • Cooling • Heating • All of the above

Last Answer : cooling

For same compression ratio and for same heat added  (a) Otto cycle is more efficient than Diesel cycle  (b) Diesel cycle is more efficient than Otto cycle  (c) efficiency depends on other factors  (d) both Otto and Diesel cycles are equally efficient  (e) none of the above.

Description : For same compression ratio and for same heat added  (a) Otto cycle is more efficient than Diesel cycle  (b) Diesel cycle is more efficient than Otto cycle  (c) efficiency depends on other factors  (d) both Otto and Diesel cycles are equally efficient  (e) none of the above.

Last Answer : Answer : a

When auto transfer is effected?

Description : When auto transfer is effected? 

Last Answer : a) When any one module trips b) When overload exceeds 175% for more than 40 msec. is existing. c) When UPS output voltage varies beyond 415v +/- 10% 

If the size of the elements is small, the final solution is expected to be accurate. a.more b.less c.depends on other factors d.can't say

Description : If the size of the elements is small, the final solution is expected to be accurate. a.more b.less c.depends on other factors d.can't say

Last Answer : a.more

If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to Carnot cycle  (a) more  (b) less  (c) equal  (d) depends on other factors  (e) none of the above.

Description : If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to Carnot cycle  (a) more  (b) less  (c) equal  (d) depends on other factors  (e) none of the above.

Last Answer : Answer : c

In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate. (A) Increases (B) Decreases (C) Does not affect (D) May increase or decrease, depends on the type of baffle

Description : In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate. (A) Increases (B) Decreases (C) Does not affect (D) May increase or decrease, depends on the type of baffle

Last Answer : (A) Increases

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

Description : 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 ... nucleate boiling depends basically on the ease with which the bubbles are formed and detached from the heating surface

Last Answer : (B) The equivalent diameter of heat transfer for a duct of square cross￾section (having each side as 'x') is equal to 4x

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

Description : 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

Last Answer : (D) (ΔT) 3/4

Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta °C depends on (A) T1 - T2 (B) T1 - Ta (C) T2 - Ta (D) None of these

Description : Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta °C depends on (A) T1 - T2 (B) T1 - Ta (C) T2 - Ta (D) None of these

Last Answer : (D) None of these

In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient (A) Increases (B) Decreases (C) Is not affected (D) May increase or decrease; depends on the feed

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Crystal size in a continuous crystalliser depends upon the (A) Rate of heat transfer (B) Degree of turbulence (C) Degree of super-saturation (D) All (A), (B) and (C)

Description : Crystal size in a continuous crystalliser depends upon the (A) Rate of heat transfer (B) Degree of turbulence (C) Degree of super-saturation (D) All (A), (B) and (C)

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

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

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

Last Answer : (A) Re, Pr

Economy of a multiple effect evaporator depends upon the (A) Heat balance consideration (B) Rate of heat transfer (C) Both (A) and (B) (D) Neither (A) nor (B

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Last Answer : (A) Heat balance consideration

jH factor for heat transfer depends upon the __________ number. (A) Biot (B) Nusselt (C) Reynolds (D) Prandtl

Description : jH factor for heat transfer depends upon the __________ number. (A) Biot (B) Nusselt (C) Reynolds (D) Prandtl

Last Answer : (C) Reynolds

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

Description : 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

Last Answer : (C) Radiation

In mid-latitudes, convective precipitation is associated with which front? -Do You Know?

Description : In mid-latitudes, convective precipitation is associated with which front? -Do You Know?

Last Answer : answer:

What is the name of Frozen rain droplets created by the up draft of convective thunderstorms?

Description : What is the name of Frozen rain droplets created by the up draft of convective thunderstorms?

Last Answer : They're called hailstones.

What arrangement of material may lead to convective motion?

Description : What arrangement of material may lead to convective motion?

Last Answer : denser material on top of less dense material

Cherapunji receives more rainfall than Shillong because: (a) the former is nearer to the sea (b) the air of different densities and temperature tends to converge towards Cherapunjl from different direction during the rainy season (c) Cherapunji is located on the windward side (d) convective precipitation brings more rain at Cherapunji

Description : Cherapunji receives more rainfall than Shillong because: (a) the former is nearer to the sea (b) the air of different densities and temperature tends to converge towards Cherapunjl from ... Cherapunji is located on the windward side (d) convective precipitation brings more rain at Cherapunji

Last Answer : Ans: (b)

In mid-latitudes, convective precipitation is associated with which front?

Description : In mid-latitudes, convective precipitation is associated with which front?

Last Answer : Cold fronts

What causes convective acceleration in fluid flow? (A) Steep slope in flow (B) Unsteady nature of flow (C) Non-uniformity of flow (D) Turbulence in flow

Description : What causes convective acceleration in fluid flow? (A) Steep slope in flow (B) Unsteady nature of flow (C) Non-uniformity of flow (D) Turbulence in flow

Last Answer : (C) Non-uniformity of flow

The component of acceleration resulting due to unsteady nature of flow is called __________ acceleration. (A) Normal (B) Local (C) Convective (D) Tangential

Description : The component of acceleration resulting due to unsteady nature of flow is called __________ acceleration. (A) Normal (B) Local (C) Convective (D) Tangential

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Precipitation caused due to upward movement of warmer air as compared to surrounding air, is called (A) Cyclonic precipitation (B) Convective precipitation (C) Orographic precipitation (D) None of these

Description : Precipitation caused due to upward movement of warmer air as compared to surrounding air, is called (A) Cyclonic precipitation (B) Convective precipitation (C) Orographic precipitation (D) None of these

Last Answer : Answer: Option B

Precipitation caused by lifting of an air mass due to the pressure difference, is called (A) Cyclonic precipitation (B) Convective precipitation (C) Orographic precipitation (D) None of these

Description : Precipitation caused by lifting of an air mass due to the pressure difference, is called (A) Cyclonic precipitation (B) Convective precipitation (C) Orographic precipitation (D) None of these

Last Answer : Answer: Option A

Precipitation caused due to striking of air masses with a topographical feature, is called (A) Orographic precipitation (B) Convective precipitation (C) Cyclonic precipitation (D) None of these

Description : Precipitation caused due to striking of air masses with a topographical feature, is called (A) Orographic precipitation (B) Convective precipitation (C) Cyclonic precipitation (D) None of these

Last Answer : Option A

The hyperboloid shape also aids in accelerating the upward convective air flow, improving __________ efficiency. a. Heating b. Warming c. Cooling d. Cold

Description : The hyperboloid shape also aids in accelerating the upward convective air flow, improving __________ efficiency. a. Heating b. Warming c. Cooling d. Cold

Last Answer : c. Cooling

In an area of converging air a. Clouds cannot be formed b. Clouds can be formed c. Convective clouds can be dissolved d. Stratified clouds can be dissolved

Description : In an area of converging air  a. Clouds cannot be formed  b. Clouds can be formed  c. Convective clouds can be dissolved  d. Stratified clouds can be dissolved

Last Answer : b. Clouds can be formed

In an area of converging air a. Clouds cannot be formed b. Clouds can be formed c. Convective clouds can be dissolved d. Stratified clouds can be dissolved

Description : In an area of converging air a. Clouds cannot be formed b. Clouds can be formed c. Convective clouds can be dissolved d. Stratified clouds can be dissolved

Last Answer : b. Clouds can be formed

At lower temperatures and pressures, the latent heat of vaporization of a refrigerant (a) decreases (b) increases (c) remains same (d) depends on other factors

Description : At lower temperatures and pressures, the latent heat of vaporization of a refrigerant (a) decreases (b) increases (c) remains same (d) depends on other factors

Last Answer : Ans: b

On which factors heat content of a system depends?

Description : On which factors heat content of a system depends?

Last Answer : Ans: Heat content (enthalpy of a reaction depends upon two factors I. Physical state of reactants II. Temperature

What for Schmidt plot for is used in heat transfer problems ?

Description : What for Schmidt plot for is used in heat transfer problems ?

Last Answer : Schmidt plot is a graphical method for determining the temperature at any point in a body at a specified time during the transient heating or cooling period.

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

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

Last Answer : Get doubled.

Cooling towers operate through a ____process that efficiently cools the already cycled water to be reused. 1. Heat exchange 2. Heat expand 3. Heat transfer 4. None of above

Description : Cooling towers operate through a ____process that efficiently cools the already cycled water to be reused. 1. Heat exchange 2. Heat expand 3. Heat transfer 4. None of above

Last Answer : Heat transfer

An ideal gas is compressed in a cylinder so well insulated that there is essentially no heat transfer. The temperature of gas  a. Remains constant  b. increases  c. decreases  d. is basically zero

Description : An ideal gas is compressed in a cylinder so well insulated that there is essentially no heat transfer. The temperature of gas  a. Remains constant  b. increases  c. decreases  d. is basically zero

Last Answer : increases

Which of the following occurs in a reversible polytrophic process?  a. Enthalpy remains constant  b. Internal energy does not change  c. Some heat transfer occurs  d. Entropy remains constant

Description : Which of the following occurs in a reversible polytrophic process?  a. Enthalpy remains constant  b. Internal energy does not change  c. Some heat transfer occurs  d. Entropy remains constant

Last Answer : Some heat transfer occurs

When the expansion of compression of gas takes place without transfer of heat to or from the gas the process is called  a. reversible  b. adiabatic  c. polytropic  d. isothermal

Description : When the expansion of compression of gas takes place without transfer of heat to or from the gas the process is called  a. reversible  b. adiabatic  c. polytropic  d. isothermal

Last Answer : adiabatic

When the expansion of compression of gas takes place without transfer of heat or from the gas the process is called;  a. Isometric process  b. Isothermal process  c. Isobaric process  d. Adiabatic process

Description : When the expansion of compression of gas takes place without transfer of heat or from the gas the process is called;  a. Isometric process  b. Isothermal process  c. Isobaric process  d. Adiabatic process

Last Answer : Adiabatic process

Which of the following best describes heat?  a. The capacity to do work  b. Forces times distances  c. Sum of thermal and chemical energy  d. An energy transfer due to temperature difference

Description : Which of the following best describes heat?  a. The capacity to do work  b. Forces times distances  c. Sum of thermal and chemical energy  d. An energy transfer due to temperature difference

Last Answer : An energy transfer due to temperature difference

The process that has no heat transfer  a. Density  b. Isentropic Process  c. Isometric Process  d. Adiabatic

Description : The process that has no heat transfer  a. Density  b. Isentropic Process  c. Isometric Process  d. Adiabatic

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The first law of thermodynamics may be expressed in the following equivalent  a. the net heat transfer id equal to the network  b. the sum of the total energy forms leaving the system boundary is always equal to the energy input  c. energy can neither be created nor destroyed but only converted from one form to another  d. all of the above

Description : The first law of thermodynamics may be expressed in the following equivalent  a. the net heat transfer id equal to the network  b. the sum of the total energy forms leaving the system boundary is ... neither be created nor destroyed but only converted from one form to another  d. all of the above

Last Answer : all of the above