Section 4 Flashcards
In common bubble cap distillation column design practice, riser area is approximately equal to (where, Aa = Annular passage area, and Sa = Slot area)
Aa = Sa
Heat transfer co-efficient, hG(Kcal/hr.m2 .°C) and mass velocity of air, G (kg/hr.m2 ) for air flow parallel to the surface in case of constant drying rate in batch drying is related as hG = 0.0176G^(0.8). But when the flow of air perpendicular to the surface is encountered, this equation changes to
hG = 1.004 G^0.37
In the agitators, the power required will be changed with the increase of diameter of agitator (D) as
D^5
Apex angle of conical heads used in the bottom heads of chemical process equipments is usually
60°
Pressure drop due to pipe fittings can be estimated by the equation, dP/p = 4f * Le/D * V^2/2gc
, where, Le = equivalent length of straight pipeline which will incur the same frictional loss as the fitting and D = diameter of the fitting. The value of (dimensionless) for 45° elbow and 180° close return bends would be respectively around
45 and 75
A pressure vessel is said to be made of ‘thick’ shell, if the ratio of its diameter to wall thickness is
10
Rate of filtrate delivery is inversely proportional to the
viscosity of filtrate.
cake & filter medium resistance
Tube side heat transfer co-efficient for turbulent flow of liquid through tubes is proportional to
G^0.80
Circumferential (hoop) stress in a thin cylindrical vessel under internal pressure is __________ the longitudinal stress.
twice
The dust collection efficiency of electrostatic precipitator increases with increase in the
electrode area.
For storing hazardous chemicals in large storage tanks, the minimum safe distance between the two tanks should range between __________ times the tank diameter.
1 to 1.5
Which of the following factors determine the amount of entrainment in a distillation column ?
Plate spacing.
Depth of liquid above the bubble cap slots.
Vapour velocity in the volume between the plates.
The absorption factor is defined as (where, S1 = slope of the equilibrium curve, S2 = slope of the operating line)
S1/S2
In shell and tube heat exchangers, straight tie rods are used to
hold baffle in space.
In a rotary drier, the average retention time of solid is(where Z = length of the drier, metres ρ = apparent solid density, kg/m3 L = flow rate of dry solids, kg/see. m2 drier cross-section H = hold up of solid.)
(ZHp)/L
In case of design of a shell and tube heat exchanger,
A. minimum cleaning lane of 6.5 mm is provided, when tubes are on a square pitch.
B. minimum tube sheet thickness (in which tubes are fixed) is equal to the O.D. of the tube upto 15 mm tube diameter; and for > 15 mm tube diameter, tube sheet thickness is smaller than tube diameter.
C. O.D. of the tube is 6 to 40 mm while the tube lengths used are 0.5, 2.5, 3.0, 4.0, 5.0, 6 metres.
D. all (a), (b) & (c).
D. all (a), (b) & (c).
In a cylinderical vessel subjected to internal pressure, the longitudinal stress σL and the circumferential stress, σn are related by
σh = 2 σL
Nominal size of a pipe is an indication of its __________ diameter.
approximate
Excessive liquid gradient on a tray may result in the
maldistribution of gas.
back trapping.
gas blowing beneath cap skit.
all (a), (b) and (c).
all (a), (b) and (c).
The ratio of tube length to shell diameter in case of liquid shell and tube heat exchanger ranges from
4 to 8
In a double pipe concentric heat exchanger, the equivalent diameter of annulus for heat transfer would be (where, D1 and D2 are I.D. of inner and outer pipes)
(D2^2 - D1^2)/D1^2
squared
What is the slope of the operating line in the stripping section of a distillation column ?
> 1
__________ shaped roof is most commonly used for cylindrical tanks.
Cone
.
In a thin cylindrical shell, the hoop stress is __________ stress.
circumferential tensile
Commercial packed scrubbers are normally designed for a pressure drop range of __________ mm water coloumn per metre of packed height.
17-34
The retention time of material in a rotary dryer depends upon its
A. rpm
B. slope & length
C. flights arrangement
In actual operation of a bubble cap distillation tower, the __________ at the bottom of the tower is more than that at the top of the tower.
A. molal flow rate of vapour
B. vapour molecular weight
C. pressure and temperature
Rotary driers are most economically designed for the number of heat transfer units (HTU) from
1.5 to 2.5
The difficulty of liquid distribution in packed towers is accentuated, when the ratio of tower diameter to packing diameter is
< 7
An increase in the liquid resistance to interphase mass transfer and a resultant reduction in plate efficiency is caused by
A. an increase in liquid viscosity.
B. an increase in relatived volatility for rectification columns.
C. decrease in gas solubility for absorbers.
D. all (a), (b) and (c).
D. all (a), (b) and (c).
In the design of a bag filter, the gas temperature is an important consideration, as it affects the
A. gas density
B. gas viscosity
C. fibre selection
D. all (a), (b) & (c)
D. all (a), (b) & (c)
With increase in temperature drop (in a shell and tube heat exchanger), the LMTD correction factor, FT
decreases very rapidly
The normal range of velocity of steam in pipes is __________ m/sec.
80-100
__________ dished head is the strongest of all.
Hemispherical
Pick out the correct statement.
A. It is preferred to use a vertical condenser for condensation of vapor from a distillation column without sub-cooling
B. Draining of residual liquid on tray during shut down of distillation column is facilitated by weep holes.
C. Random packing a packed tower offers the advantage of lower pressure drop and higher throughput of fluids as compared to regular/stacked packing.
D. Risers are generally not connected to the plate in a distillation coloumn by bolts, rivets or welding.
D
“A claming section” before the liquid flows into the downcomer is privided to
permit release of entrained vapour in the liquid.
The units of Young’s modulus of elasticity and __________ are the same.
stress
In the design of a shell and tube heat exchanger, the corrosion allowance
A. need not be provided for non-pressure parts like tie rods, spacers, baffles, supports etc.
B. for carbon steel and cast iron pressure parts is 1.5 mm (except for tubes) and for severe conditions it is 3 mm.
C. for internal cover and tube sheet is provided on both the sides.
D. all (a), (b) & (c).
D. all (a), (b) & (c).
Vertical condenser is advantageous to the horizontal condenser from operation point of view, when
both the functions of condensation & sub cooling are carried out in a single unit.
Hazards associated with the relief valve leakage for extremely hazardous material storage can be taken care of by providing
rupture diaphragm
Minimum baffle spacing recommended in a shell and tube heat exchanger is equal to
5 cms
__________ liquor is best handled in a long tube vertical evaporator
Foamy
Theoretically calculated diameter of the stripping section of the continuous rectification column is __________ that of the enriching section.
more than
Hold up of material in a operating rotary drier is in the range of
0.05 to 0.15
A binary liquid azeotropic mixture has boiling point higher than either of the components, when it shows __________ deviation from Raoult’s Law.
negative
The testing pressure of storage tanks and pressure vessels designed as per Indian standard codes should be about __________ times.the design pressure.
1.5 to 2
Flanges are connected to pipes by
screwing
welding
brazing
The ratio of down take area to cross-sectional area of the tube, for calendria type evaporator ranges from
0.5 to 1
Shortest distance between two tubes is
called tube clearance.
