Q.1
Pick out the wrong statement.
Q.2
The equivalent diameter for pressure drop is __________ that for heat transfer.
Q.3
In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate.
Q.4
A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of
Q.5
The film co-efficient between condensing vapour and metal wall increases with
Q.6
What is the absorptivity of a black body?
Q.7
For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then
Q.8
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
Q.9
A 2-4 heat exchanger involves
Q.10
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as
Q.11
Pick out the wrong statement.
Q.12
The equation, Nst = f/2, is the __________ analogy.
Q.13
The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy.
Q.14
In a heat exchanger, floating head is provided to
Q.15
The separation of liquid droplets from the vapor is done by a/an __________ , in the evaporators.
Q.16
The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoffs law.
Q.17
Radiator of an automobile engine is a __________ type of heat exchanger.
Q.18
Trap is used to remove __________ from steam pipe lines.
Q.19
According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor)
Q.20
Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.
Q.21
In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger.
Q.22
Thermal conductivities of most of the liquids __________ with rise in temperature.
Q.23
Heat transfer rate described by Fourier's law will decrease, if the __________ increases.
Q.24
In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased.
Q.25
The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is
Q.26
Heat flux, as defined in heat flow is analogous to __________ in electricity flow.
Q.27
In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will
Q.28
A graph between __________ is called Wilson plot.
Q.29
In forced convection, the heat transfer depends on
Q.30
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
Q.31
Condensing film co-efficient for steam on horizontal tubes ranges from 5000 to 15000 Kcal/hr.m² .°C. Condensation of vapor is carried out inside the tube in a shell and tube heat exchanger, when the
Q.32
If a single tube pass heat exchanger is converted to two pass, then for the same flow rate, the pressure drop per unit length in tube side will
Q.33
In a backward feed multiple effect evaporator
Q.34
Which type of heat exchanger is preferred for heavy heat loads?
Q.35
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface tempeature follows __________ law.
Q.36
In a single effect evaporator, the economy is
Q.37
Calburn analogy is applicable for the value of Prandtl number from
Q.38
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is
Q.39
With increase in temperature, the thermal conductivity of a gas
Q.40
With increase in temperature, the thermal conductivity of steel
Q.41
The thermal radiation emitted by a body is proportional to Tn, where T is its absolute temperature. The value of 'n' is exactly 4 for
Q.42
Convective heat transfer, in which heat is transferred by movement of warmed matter is described by
Q.43
A steel sphere of radius 0.1 m at 400°K is immersed in an oil at 300°K. If the centre of the sphere reaches 350°K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions ? Assume that the conductive heat transfer co-efficient is infinitely large.
Q.44
Boiling point elevation of an ideal solution
Q.45
Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator.
Q.46
Film condensation is promoted on a/an __________ surface.
Q.47
Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.)
Q.48
Baffles are provided in heat exchangers to increase the
Q.49
What is the geometric mean of two heat transfer areas A₁ and A₂ ?
Q.50
Increasing the liquor level in the evaporator results in the
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