Q1: Heat exchangers operating, when the asymptotic range is reached,

ANS:B - results in making part of the heating surface inactive.

When the asymptotic range is reached in heat exchangers, it typically results in making part of the heating surface inactive. The asymptotic range refers to the condition where the temperature difference between the hot and cold fluids approaches zero as they pass through the heat exchanger. In this range, the driving force for heat transfer diminishes, leading to reduced heat transfer rates. As a result, certain portions of the heating surface may become inactive, meaning that heat transfer no longer occurs in those regions. This can happen because the temperature of the hot fluid approaches the temperature of the cold fluid, reducing the temperature gradient across the heat exchanger and limiting heat transfer in certain areas. Therefore, when the asymptotic range is reached, it often results in making part of the heating surface inactive.