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________________?

Byadmin March 2, 2019August 24, 2021

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.

Chemical Heat Transfer

LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?

LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?

A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)
B. Outlet temperature of both the hot and cold fluid are same
C. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid
D. None of these

Read More LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?
Chemical Heat Transfer

Increasing the liquor level in the evaporator results in the_______________?

Increasing the liquor level in the evaporator results in the_______________?

A. Decreased capacity
B. Increase in liquor film co-efficient
C. Decreased effect of hydrostatic head
D. Increased true temperature drop

Read More Increasing the liquor level in the evaporator results in the_______________?
Chemical Heat Transfer

The rate of emission of radiation by a body does not depend upon the__________________?

The rate of emission of radiation by a body does not depend upon the__________________?

A. Wavelength of radiation
B. Surface temperature of the body
C. Nature of the surface
D. Shape and porosity of the body

Read More The rate of emission of radiation by a body does not depend upon the__________________?
Chemical Heat Transfer

A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time ___________________?

A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time ___________________?

A. t = 283 s
B. t = 356 s
C. t = 400 s
D. t = 800 s

Read More A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time ___________________?
Chemical Heat Transfer

It is not preferable to use superheated steam in evaporators, because of its very_________________?

It is not preferable to use superheated steam in evaporators, because of its very_________________?

A. High temperature
B. High pressure
C. Low film co-efficient
D. None of these

Read More It is not preferable to use superheated steam in evaporators, because of its very_________________?
Chemical Heat Transfer

Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is_____________?

Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is_____________?

A. Vertical heat exchanger with steam on tube side
B. Vertical heat exchanger with steam on shell side
C. Horizontal heat exchanger with steam on tube side
D. Horizontal heat exchanger with steam on shell side

Read More Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is_____________?

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