Evaporator
An evaporator is a type of heat exchanger device that facilitates evaporation by utilizing conductive and convective heat transfer to provide the necessary thermal energy for phase transition from liquid to vapor. 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 through the tube walls to the liquid inside via conduction, providing the thermal energy needed for evaporation. Convective currents inside also contribute to heat transfer efficiency.
There are various evaporator designs suitable for different applications. Shell and tube, plate, and flooded evaporators are commonly used in industrial processes like desalination, power generation, and air conditioning. Plate-type evaporators offer compactness while multi-stage designs enable enhanced evaporation rates at lower heat duties. Overall evaporator performance is dependent on factors such as heat transfer coefficient, tube/plate material properties, flow regime, and vapor quality achieved.
Advanced control techniques such as online fouling detection are utilized to maintain evaporator thermal performance over time. CFD modeling and new surface coating technologies also continue improving heat and mass transfer capabilities for more energy efficient vapor generation. Evaporators remain an essential unit operation across many industries owing to their ability to separate mixed phases through a controlled phase change process.