Evaporator

An evaporator is a heat exchanger that uses heat input to vaporize a liquid at reduced pressure. It serves to remove solvent or water from liquids, concentrate solutions, and function as a key component in refrigeration and air conditioning systems. In HVAC and refrigeration, the evaporator is where the refrigerant absorbs heat from the surroundings and boils into vapor. In process industries, evaporators concentrate streams by evaporating the solvent, often water.

In a typical refrigeration cycle, low-pressure liquid refrigerant enters the evaporator and absorbs heat from the air or process stream, causing it to boil. The resulting vapor returns to the compressor to be recompressed and circulated. Design considerations include the heat transfer area and rate, surface geometry and finning, refrigerant charge, and the control of superheat to protect the compressor.

Common configurations include flooded evaporators, dry-expansion evaporators, falling-film and rising-film types, and multi-effect systems that reuse latent heat to improve energy efficiency. Industrial evaporators may employ mechanical vapor recompression or thermal vapor compression to increase efficiency and capacity.

Operational issues include fouling from deposits, scale, or biofilms, corrosion, and excessive pressure drop. Maintenance focuses on cleaning and descaling, inspecting connections for leaks, and verifying refrigerant charge and seals. Safety considerations cover the handling of refrigerants, high temperatures and pressures, and compatibility of materials with corrosive or solvent streams.