Pick out the wrong statement.
A. In drying a solid containing moisture above the critical moisture content the number of degrees of freedom is 2
B. Sherwood number in mass transfer corresponds to Nusselt number in heat transfer and Schmidt number to Prandtl number
C. Forced convection is relatively more effective in increasing the rate of mass transfer, if Schmidt number is larger
D. Hot gases at moderate pressure are usually in the shell side of shell and tube heat exchangers. At higher pressure, however, it is customary to put gas in the tube side
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Multipass heat exchangers are used
A. Because of simplicity of fabrication
B. For low heat load
C. To obtain higher heat transfer co-efficient and shorter tube
D. To reduce the pressure drop
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Steam economy in case of a triple effect evaporator will be
A. 1
B. < 1
C. > 1
D. Between 0 and 1
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Kirchoff's law is applicable to
A. Monochromatic radiation only
B. Total radiation only
C. Both A and B
D. Only volumes and not to surfaces
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The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
A. ∝ t
B. ∝ t 1
C. D. Independent of 't'
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The Grashoff number is defined as the ratio of the
A. Buoyancy to inertial forces
B. Buoyancy to viscous forces
C. Inertial to viscous forces
D. Buoyancy to surface tension forces
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A __________ surface has the maximum thermal emissivity out of the following.
A. Black & smooth
B. Black & rough
C. White & smooth
D. White & rough
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Which of the following has maximum thermal conductivity at the same temperature?
A. Steel
B. Petrol
C. Air
D. All of the above
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As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the
A. Temperature of the body only
B. Wavelength of monochromatic radiation
C. Both A and B
D. Nature of material of body
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With increase in temperature, the thermal conductivity of fresh lubricating oil
A. Increases
B. Decreases
C. Remains unchanged
D. May increase or decrease; depends on its composition
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'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a
A. Non-dimensional factor
B. Factor of safety
C. Conversion factor for individual film heat transfer co-efficient to overall heat transfer co-efficient
D. None of these
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In a gas-liquid shell and tube heat exchanger, the
A. Presence of a non-condensible gas decreases the condensing film co-efficient
B. Gases under high pressure are routed through the tube side, because high pressure gases are corrosive in nature
C. Gases to be heated/cooled is normally routed through the shell side, because the corrosion caused by the cooling water or steam condensate remain localised to the tubes
D. All of the above
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In SI units, thermal conductivity is expressed in
A. Watt/m.°K
B. Watt/m2 .°K
C. Watt/m3 .°K
D. Watt/m4 .°K
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With increase in temperature, the thermal conductivity of most liquids
A. Increases
B. Decreases
C. Remains same
D. First increases upto a certain temperature and then becomes constant
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Which of the following has the lowest overall heat transfer co-efficient?
A. Dowtherm
B. Molten sodium
C. Water
D. Air
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Pick out the correct statement.
A. 1 kcal/hr.m.°C is equal to 1 BTU/hr. ft.°F
B. In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity
C. In unsteady state heat conduction, heat flows in the direction of temperature rise
D. In heat transfer by forced convection, Grashoff number is very important
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Value of Prandtl number for water ranges from
A. 1 to 2
B. 5 to 10
C. 100 to 500
D. 1000 to 2000
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1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C.
A. 1.49
B. 1
C. 4.88
D. None of these
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A process stream of dilute aqueous solution flowing at the rate of 10 Kg.s-1 is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s-1 . A 1 - 1 shell and tube heat exchanger is available. The best arrangement is
A. Counter flow with process stream on shell side
B. Counter flow with process stream on tube side
C. Parallel flow with process stream on shell side
D. Parallel flow with process stream on tube side
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Low thermal conductivity of heat insulating materials is due to its
A. Dense structure
B. High proportion of air space
C. High specific heat
D. None of these
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