Q1: In case of evaporators, liquid entrainment results primarily due to

ANS:C - foaming of the solution.

Liquid entrainment in evaporators primarily results from foaming of the solution. Foaming occurs when bubbles of vapor become trapped within the liquid phase, causing the mixture to foam and carry liquid droplets with it. This phenomenon is often observed in evaporators when the boiling liquid contains substances that promote the formation of stable foam, such as surfactants or dissolved solids. High vacuum in the evaporator may contribute to liquid entrainment by lowering the boiling point of the liquid, but it is not the primary cause. High evaporation rate and high heat transfer rate are factors that can increase the likelihood of liquid entrainment, but they are not the direct causes. Therefore, the correct option is: "foaming of the solution."