It is not desirable to design a heat exchanger for LMTD correction factor, FT, o

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Question
It is not desirable to design a heat exchanger for LMTD correction factor, F_T, of less than
Options
A. 0.99
B. 0.95
C. 0.80
D. 0.55

Correct Answer

0.80

1. 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.
Options
A. The pressure drop due to the caps & slots and the static submergence should be as high as practicable for reasonable operation.
B. 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.
C. The dimensionless ratio of liquid gradient to pressure drop head caused by the bubble cap assembly should be less than 0.4.
D. none of these.

2. Correct use of 'factor of safety' is very important in equipment design. It is defined as the ratio of the
Options
A. ultimate stress to breaking stress.
B. ultimate stress to working stress.
C. working stress to ultimate stress.
D. none of these.

3. Pick out the wrong statement pertaining to the use of valve tray, seive tray and bubble cap trays in continuous distillation column.
Options
A. Bubble cap trays though most expensive are the best in situations, where low vapour rates is to be handled and a positive liquid seal is essential at all flow rates.
B. Murphree efficiency of all the three trays are nearly equal, however the peak efficiency is generally higher for seive and valve trays than the bubble cap.
C. Maintenance cost for valve and seive trays are comparatively more than bubble cap tray due to their relatively complicated construction features.
D. Valve trays have the highest turn down ratio (i.e. the ratio of the highest to the lowest vapour flow rates) and thus provides the maximum flexible operating range.

8. Which of the following is not a valid assumption in continuous binary distillation for calculating the number of equilibrium stages by Mc-Cabe-Thiele's method?
Options
A. Sensible heat changes for vapour & liquid are negligibly small.
B. Reflux is not a saturated liquid.
C. Molar latent heat of the two components are equal.
D. Heat of mixing of normal liquid is assumed to be zero.

10. For laminar flow (N_Re < 2100) in steel pipe, the optimum inside pipe diameter is given by
Options
A. D_{i, opt} = 3 Q^0.36 ?^0.18
B. D_{i, opt} = 3.9 Q^0.45 . ?^0.23
C. D_{i, opt} = 7.6 Q^0.36 . ?^0.9
D. D_{i, opt} = 3 Q^0.36 . ?^1.86 ?^0.08

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