Q.1
What is the thermal conductivity of a perfect heat insulator?
Q.2
Crystal size in a continuous crystalliser depends upon the
Q.3
For heat flow through very thick walled cylinder, use____mean radius.
Q.4
The ratio of kinematic viscosity to thermal diffusivity is called the __________ number.
Q.5
The main function of baffles provided in a shell and tube heat exchanger is to
Q.6
The maximum heat transfer co-efficient from steam heating will be attained when the steam is
Q.7
At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the
Q.8
When vaporisation takes place directly at the heating surface, it is called
Q.9
Which is the most suitable for the con-certration of highly concentrated solution?
Q.10
Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because
Q.11
For a laminar flow of fluid in a circular tube, 'h₁' is the convective heat transfer co-efficient at velocity 'V₁'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is
Q.12
Tube expansion allowances exist in __________ heat exchanger.
Q.13
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell)
Q.14
In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell)
Q.15
Tube pitch is the __________ of tube diameters and the clearances.
Q.16
The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film )
Q.17
(NGr x NPr) is called the __________ number.
Q.18
The rate of emission of radiation by a body does not depend upon the
Q.19
In a multiple effect evaporator, the effect of boiling point elevation is to
Q.20
Pick out the wrong statement.
Q.21
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
Q.22
200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 x 10⁻³ kg/m².s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m²/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)
Q.23
It is desired to concentrate a 20% salt solution (20 kg of salt in 100 kg of solution) to a 30% salt solution in an evaporator. Consider a feed of 300 kg/min at 30°C. The boiling point of the solution is 110°C, the latent heat of vaporisation is 2100 kJ/kg and the specific heat of the solution is 4 kJ/kg.K. The rate at which the heat has to be supplied in (kJ/min) to the evaporator is
Q.24
If h₁ = inner film co-efficient and /h₂ = outer film co-efficient, then the overall heat transfer co-efficient is
Q.25
Mode of heat transfer involved in the cooling of air cooled internal combustion engine is
Q.26
A BTU/hr.ft.2 °F is equal to
Q.27
A dephlegmator is a
Q.28
Vacuum is generally maintained in the vapour space of an evaporator mainly to
Q.29
Prandtl and Reynold's analogies are identical for Prandtl number value of
Q.30
The thermal radiative flux from a surface of emissivity = 0.4 is 22.68 kW/m². The approximate surface temperature (K) is
(Stefan-Boltzman constant = 5.67xl0⁻⁸ W/m².K⁴)
Q.31
Which of the following is concerned with both heat and mass transfer?
Q.32
An ejector is used to
Q.33
An insulator should have
Q.34
Shell side pressure drop in a shell and tube heat exchanger does not depend upon the
Q.35
Evaporation of 1kg of water from a solution in a single effect evaporator requires about __________ kg of steam.
Q.36
Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K )
Q.37
Fqra cold viscous feed, backward feed gives __________ than forward feed.
Q.38
In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to __________ the velocity head.
Q.39
Terminal point temperature differences between fluids in case of a heat exchanger is termed as
Q.40
Nusselt number for full developed, laminar, constant property flow in a pipe at uniform heat flux is
Q.41
Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is
Q.42
In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient
Q.43
Dietus-Boelter equation cannot be used for molten metals mainly due to its very low
Q.44
A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case,
Q.45
The film thickness for laminar film condensation on vertical surface __________ from top to bottom.
Q.46
The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.
Q.47
Viscosity of gases __________ with increase in temperature.
Q.48
Thermal conductivity of a gas at low density, __________ with increase in temperature.
Q.49
For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it
Q.50
At constant temperature, the thermal conductivities of gases __________ with rise in pressure.
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