Economy of a multiple effect evaporator is not influenced much by the

The correct answer is:

D. Ratio of the weight of the thin liquor to thick liquor

Explanation:
The economy of a multiple effect evaporator is defined as:

Economy = kg of water vaporized / kg of steam used

It depends primarily on factors that affect heat utilization efficiency, such as:

Boiling Point Elevation (A): Reduces the effective temperature driving force in each effect → affects economy.

Temperature of the Feed (B): Cold feed consumes more steam for heating → affects economy.

Rate of Heat Transfer (C): Determines how fast vaporization occurs → affects economy.

However:

D. Ratio of the weight of the thin liquor to thick liquor:
This ratio affects capacity and design (like residence time, flow rate, and equipment sizing), but it does not significantly influence the steam economy.

✅ Therefore, the least influential factor on economy is:
D. Ratio of the weight of the thin liquor to thick liquor.