What is an evaporator and what are its main types?

An evaporator concentrates a solution by vaporizing the solvent (usually water) using heat. Main types include: Natural circulation (liquid circulates by density difference, simple but low capacity), Forced circulation (pump provides flow, handles viscous/fouling liquids), Falling film (liquid flows down tube walls as film, excellent for heat-sensitive products), Rising film (liquid/vapor rise together, high heat transfer), and Agitated thin film (wiped surface for very viscous materials). Selection depends on feed properties, fouling tendency, and heat sensitivity.