ANS:B - increases in winter

For the same process conditions, the reflux ratio of an unlagged distillation column increases in winter. Here's why:

1. Temperature Difference: In winter, the external temperature is generally lower compared to summer. In an unlagged distillation column, the temperature difference between the external environment and the column affects the condensation rate and thus the reflux ratio.
2. Higher Condensation Rate in Winter: In colder temperatures, the condensation rate of the overhead vapor (reflux) is higher because the temperature difference between the vapor and the surrounding environment is greater. As a result, more vapor condenses back into liquid, leading to an increased reflux ratio.
3. Stability of Process Conditions: Assuming the process conditions remain constant, the increased reflux ratio in winter helps maintain stability and efficiency in the distillation column by providing more liquid reflux for better separation of components.