Which of the following is generally considered as opaque surface towards radiations ?

Related Mcqs:

Pick out the wrong statement?

A. Fluid movement under the influence of buoyant forces resulting from change in density takes place in case of natural convection B. The ratio NNu/NRe . Npr is called the Stanton number C. The Peclet number is a measure of the ratio of energy transport by convection to that by conduction D. The Colburn jH … Pick out the wrong statement?Read More...

The inner wall of a furnace is at a temperature of 700°C. The composite wall is made of two substances, 10 and 20 cm thick with thermal conductivities of 0.05 and 0.1 W.m-1.°C- 1 respectively. The ambient air is at 30°C and the heat transfer co-efficient between the outer surface of wall and air is 20 W.m-2.°C-1. The rate of heat loss from the outer surface in W.m-2is__________________?

A. 165.4 B. 167.5 C. 172.5 D. 175...

For heat flow through very thick walled cylinder, use ___________mean radius?

A. Arithmetic B. Logarithmic C. Geometric D. Either A. or C....

The interchange factor for radiation heat transfer from surface ‘x’ to surface ‘y’ in case of an infinite parallel planes with emissivities εx & εy is given by_______________?

A. εx + εy B. εx . εy C. 1/εx + 1/εy D. (εx + εy)/( εx + εy – εx . εy)...

Viscous & heat sensitive liquids are concentrated in _____________ evaporators?

A. Open pan B. Long tube C. Agitated film D. None of these...