Heat And Mass Transfer - Study Mode
[#91] A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,
Correct Answer
(A) The better insulation must be put inside
Explanation
Solution: A steam pipe is to be lined with two layers of insulating materials of different thermal conductivities. For the minimum heat transfer,The better insulation must be put inside
[#92] The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to
Correct Answer
(A) Stanton number
Explanation
Solution: The ratio of Nusselt number and the product of Reynold's number and Prandtl number is equal to Stanton number
The Stanton number is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid.
[#93] The product of Reynolds number and Prandtl number is known as
Correct Answer
(C) Peclet number
Explanation
Solution: The product of Reynolds number and Prandtl number is known as Peclet number Peclet number, Pe, is a dimensionless group representing the ratio of heat transfer by motion of a fluid to heat transfer by thermal conduction
[#94] Upto the critical radius of insulation,
Correct Answer
(A) Added insulation will increase heat loss
Explanation
Solution: Upto the critical radius of insulation,Added insulation will increase heat loss It is the radius of insulation before heat transfer increases and after heat transfer decreases.
[#95] Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow and k = Thermal conductivity of the body)
Correct Answer
(A) $${ ext{kA}}frac{{{ ext{dT}}}}{{{ ext{dx}}}}$$
Explanation
Solution: Fourier's law of heat conduction is $${ ext{kA}}frac{{{ ext{dT}}}}{{{ ext{dx}}}}$$ Where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow and k = Thermal conductivity of the body. The law of heat conduction, also known as Fourier's law, states that the time rate of heat transfer through a material is proportional to the negative gradient in the temperature and to the area, at right angles to that gradient, through which the heat flows.