The critical radius 'r' of insulation on a pipe is given by
As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the
If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by
__________ paint has the maximum absorption coefficient.
What is Nusselt number ?
Steam traps are provided in steam carrying pipelines to
The Dietus-Boelter equation for convective leat transfer
cannot be used for
A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an
Radiation heat transfer rates does not depend upon the
Which of the following is correct ?
Convective heat transfer, in which heat is transferred by movement of warmed matter is described by
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient
Heat transfer rate per unit area is called
Log mean temperature difference (LMTD) cannot be used, if
In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to __________ the velocity head.
For a given ambient air temperature with increase in the thickness of insulation of a hot cylinderical pipe, the rate of heat loss from the surface would
In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is
For what value of Prandtl number, the Col-burn analogy is valid ?
In a forward feed multiple effect, the pressure build up will be
Film boiling is usually not desired in commercial equipments, because
For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is
The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at. where, K is the thermal conductivity and T is the temperature (in. oK). The units of 'a' in SI system will be
Film condensation is promoted on a/an __________ surface.
Dietus-Boelter equation cannot be used for molten metals mainly due to its very low