Process Equipment and Plant Design
In a vertical short tube evaporator (Calendria type), the

Area of central downtake is equal to 40 to 100% of total cross-sectional area of the surrounding tube
All of these
Tube dia of 2.5-7.5 cms, tube length of 75-200 cms and cylinderical drum dia of 1-6 metres are normally used
Liquor is inside the tube while the steam is outside the tube

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Process Equipment and Plant Design
Overall distillation column efficiency for most of the refinery columns can be given by (for μ = 0.07 - 1.4 cp and relative volatility < 4) (where η = overall column efficiency, % μ = molal average viscosity of feed at average column temperature and pressure, cp Δp = pressure drop per tray, psi)

Η = 1.66 - 0.25 log μ
Η = 17 - 61.1 log μ
Η = 0.25 log μ - 1.67
Η = 24.6 (Δp/μ)

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Process Equipment and Plant Design
Pick out the wrong statement pertaining to the design of the bubble cap tray of a distillation column to give stable operation and even vapour distribution.

Tendency towards stable operation is increased by increasing the skirt clearance of the caps, lowering the rate of liquid flow per unit plate width or increasing the spacing between the caps
None of these
The pressure drop due to the caps & slots and the static submergence should be as high as practicable for reasonable operation
The dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4

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