This set of Mass Transfer Questions for entrance exams focuses on “Reflux Ratio Concept (Minimum, Maximun & Optimum)”.
1. If the reflux is total, minimum stages are used.
Explanation: For total reflux no distillate formation; all the condensed vapour are sent back to fractionator.
2. At Total reflux
a) Residue is nil
b) Distillate is nil
c) Reflux is nil
d) All of the mentioned
Explanation: Total reflux there condensed vapours are sent back to column itself.
3. Reflux ratio is infinity at
a) Total reflux
b) Minimum reflux
c) Part reflux
d) None of the mentioned
Explanation: Reflux ratio becomes infinity at distillate is equals to zero. Since reflux ratio = Reflux/distillate
At distillate = 0; Reflux ratio= infinity.
4. Estimate the condenser requirement for total reflux.
a) Small condenser
b) Medium condenser
c) Large condenser
d) Partial condenser
Explanation: Since if the large condenser are used, vapour gets condensed and becomes reflux where distillate is zero.
5. For minimum reflux ratio the number of trays becomes infinite.
Explanation: For minimum reflux ratio, all the condensed vapour becomes distillate; no reflux. So it requires infinite number of trays.
6. For a minimum reflux ratio ________ condenser or reboiler loads are used.
Explanation: Since for minimum reflux ratio no reflux is produced, it’s enough to use minimum load condenser or reboiler.
Explanation: All the condensed vapours are refluxed (no distillate).
8. For finding the exact number of trays the reflux ratio should be between minimum and infinity.
Explanation: The minimum trays cannot be determined; also infinite trays are impossible; so the trays should be minimum and infinity.
9. The reflux ratio increases by increasing the reflux and decreasing the distillate.
Explanation: Reflux ratio= reflux/distillate.
Explanation: Since there is no reflux, all the condensed vapours are distillate. Then it represents minimum reflux ratio.
Sanfoundry Global Education & Learning Series – Mass Transfer.
To practice all areas of Mass Transfer for entrance exams, here is complete set of 1000+ Multiple Choice Questions and Answers