Engineering :: Mass Transfer

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21.

The diffusivity has the same dimensions as

A.	absolute viscosity	B.	kinematic viscosity
C.	density	D.	concentration

22.

The Schmidt number (NSc) is the ratio of

A.	the momentum diffusivity to the mass diffusivity	B.	the mass diffusivity to the momentum diffusivity
C.	the thermal diffusivity to the mass diffusivity	D.	the momentum diffusivity to the thermal diffusivity

23.

The Schmidt number (NSc) is defined as

A.	?/DAB	B.	?/?DAB
C.	??/DAB	D.	?DAB/?

24.

For water at 20?C the Prandtl number (NPr) is

A.	0.702	B.	7.02
C.	70.2	D.	120

25.

Peclet number (NPe) for mass transfer is defined as

A.	NRe/NSc	B.	NReNSc
C.	NSc/NRe	D.	NShNSc

26.

Stanton number (NSt) for mass transfer is defined as

A.	NSh/NReNSc)	B.	NPeNSh
C.	NSh/NSc	D.	NShNSc

27.

The eddy momentum diffusivity the thermal diffusivity and the mass diffusivity will be the same for

A.	NPr = NSc = 0.7	B.	NPr = NSc = 1
C.	NPr = NSc = 7.02	D.	NPr = NSc = 297

28.

The temperature at which a vapour-gas mixture becomes saturated when cooled at constant total pressure out of contact with a liquid is called

A.	bubble point	B.	dew point
C.	wet-bulb temperature	D.	dry-bulb temperature

29.

The dew point of an unsaturated mixture of vapour and gas does not depend on

A.	the temperature of the mixture	B.	the total pressure of the mixture
C.	the composition of the mixture	D.	all of the above

30.

The relative saturation of an unsaturated mixture of vapour and gas

A.	is always equal to its percentage saturation	B.	is always lower than its percentage saturation
C.	is always greater than its percentage saturation	D.	may be smaller or greater than its percentage saturation depending on the composition of the mixture