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An evaporator is a type of heat exchanger device that facilitates evaporation by utilizing conductive and convective heat transfer, which provides the necessary thermal energy for phase transition from liquid to vapour. Within evaporators, a circulating liquid is exposed to an atmospheric or reduced pressure environment causing it to boil at a lower temperature compared to normal atmospheric boiling.
The four main components of an evaporator assembly are:
- Tubes or channels where the refrigerant liquid is circulated
- Fins or other enhanced surfaces to increase heat transfer area
- A source of heat such as steam or combustion gases directed over the tubes
- Distillation of vapor into an outlet piping system
Heat is transferred to the liquid inside the tube walls via conduction providing the thermal energy needed for evaporation. Convective currents inside it also contribute to heat transfer efficiency.
There are various evaporator designs suitable for different applications including shell and tube, plate, and flooded evaporators, commonly used in industrial processes such as desalination, power generation and air conditioning. Plate-type evaporators offer compactness while multi-stage designs enable enhanced evaporation rates at lower heat duties. The overall performance of evaporators depends on factors such as the heat transfer coefficient, tube/plate material properties, flow regime, and achieved vapor quality.
Advanced control techniques, such as online fouling detection, help maintain evaporator thermal performance over time. Additionally, computational fluid dynamics (CFD) modeling and advancements in surface coating technologies continue to enhance heat and mass transfer capabilities, leading to more energy-efficient vapor generation. Evaporators are essential to many industries because of their ability to separate phases through a controlled phase change process.