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WorksheetsCHE481-V1-Midterm
Total questions: 20
Worksheet time: 49mins
Evaporation of 1 kg of water from a solution in a single effect evaporator requires about ________ kg of steam.
0.4 to 0.6
1 to 1.3
1.8 to 2
2 to 2.4
The maximum heat transfer coefficient from steam heating will be attained when the steam is
Supersaturated
Saturated
Wet
Subcooled
In a multiple-effect evaporator, the effect of boiling point elevation is to
Reduce the economy
Increase the economy
Multiple-effect evaporators are used to
Increase the steam economy & decrease the capacity
Increase the steam economy & the capacity
Decrease the steam economy & the capacity
Decrease the steam economy & increase the capacity
Mass transfer rate between two fluid phases does not necessarily depend on the _______ of the two phases.
chemical properties
physical properties
degree of turbulence
interfacial area
For ethanol-water system, the lowering of distillate quality from 95% to 92% will cause _______ plate requirement.
no change in theoretical
marginal decrease in the number of
major decrease in the number of
Capacity of a rotary dryer depends on its ______.
RPM
inclination with ground surface
both RPM & inclination with ground surface
neither RPM nor inclination with ground surface
The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is ________.
less
same
more
either more or less; depends on the system
200 kg of solids (on dry basis) is subjected to a drying process for a period of 5,000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 x 10^-3 kg/m^2⋅s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m^2/1,000 kg of dry solid. The moisture content at
the end of the drying period is (in kg moisture/kg dry solid) is ________.
0.5
0.05
0.1
0.2
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 _______.
3.06 × 10^5
6.12 × 10^5
7.24 × 10^5
9.08 × 10^5
The unit of heat transfer co-efficient is _______.
BTU/hr.ft^2.°F
BTU/hr.°F.ft
BTU/hr.°F
BTU/hr.ft
Which of the following is the most suitable evaporator for a highly concentrated solution?
Open pan
Long tube vertical
Agitated film
Flooding in a distillation column is detected by a sharp _______.
increase in Murphree plate efficiency
decrease in pressure drop
decrease in liquid hold up in the column
increase in pressure drop
Steam consumption in kg/hr of an evaporator is given by (where, C and E are Capacity and Economy of the evaporator respectively) ________.
C/E
E/C
CE
1/CE
A charge of 50 kmols of a mixture of benzene and chlorobenzene having 55 mol % of the less volatile is to be batch-distilled. If 25 kmols of the solution is vaporized and condensed as the distillate, calculate the concentration of the accumulated distillate. The relative volatility of benzene in the mixture is 4.15.
0.519
0.682
0.797
0.866
What is ‘Free moisture content’?
That liquid which exerts a vapor pressure less than that of the pure liquid at the given temperature.
That liquid which is removable at a given temperature and humidity.
The moisture content of cellular materials at which the cell walls are completely saturated while the cavities are liquid-free.
The maximum moisture content to which a given material can be dried under specific conditions of air temperature and humidity.
A drum dryer is designed for drying a product from an initial TS of 12% and a final moisture content of 4%. An average temperature difference between the roller surface and the product of 65°C will be used and the overall heat transfer coefficient is 1.74 kW/m2∙K. Determine the surface area of the roller required to provide a production rate of 50 kg product/hr. Assuming that about ¼ of the surface area would not be used.
2.586 m2
5.286 m2
6.258 m2
8.526 m2
What is ‘Bound moisture’ in a solid?
That liquid which exerts a vapor pressure less than that of the pure liquid at the given temperature.
That liquid which is removable at a given temperature and humidity.
The moisture content of cellular materials at which the cell walls are completely saturated while the cavities are liquid-free.
The maximum moisture content to which a given material can be dried under specific conditions of air temperature and humidity.
For a binary distillation column operating at atmospheric pressure, the temperature __________ from the bottom to the top of the column.
increases
decreases
is constant
depends on the separation
Which of the following conditions in an evaporator should be met to produce a high-quality product?
High holdup time and high-temperature operation
High holdup time and low-temperature operation
Low holdup time and high-temperature operation
Low holdup time and low-temperature operation
