An evaporator is a crucial component in a chiller or refrigeration system where the actual cooling takes place. It functions as a heat exchanger that absorbs heat from the process fluid (usually water or a water/glycol mix) circulating through the system. As the warm process fluid passes through the evaporator, heat transfers from this fluid to the refrigerant inside the evaporator.

During this heat transfer, the refrigerant evaporates-changing from a low-pressure liquid into a vapor-because it absorbs the heat from the fluid. This evaporation process cools the fluid, which then circulates back to the building or process to provide cooling.

In summary:

  • The evaporator removes unwanted heat from the chilled water or process fluid.
  • It causes the refrigerant to evaporate by absorbing heat, thus cooling the fluid.
  • The cooled fluid is then pumped to the space or equipment requiring cooling.
  • The refrigerant vapor leaves the evaporator and moves to the compressor to continue the refrigeration cycle.

There are three main types of evaporators used in industrial chillers:

Coil Type Evaporator

  • Uses coils (usually copper) immersed in a water tank.
  • Simple structure, easy maintenance, and compact design.
  • Suitable for applications where water quality is not strictly controlled.

Shell and Tube Type Evaporator

  • Consists of a bundle of tubes enclosed in a shell.
  • Water flows through the tubes while refrigerant passes around them (or vice versa).
  • Offers good heat transfer efficiency and is commonly used in large chillers25.

Plate Type Evaporator

  • Made of multiple thin, corrugated plates stacked together.
  • Provides high heat transfer efficiency due to large surface area.
  • Compact size but requires high water quality and can be harder to maintain.

Additionally, there are different operational designs within these main types:

  • Dry Type Evaporator: Refrigerant flows inside the tubes, water flows outside. Simpler and uses less refrigerant.
  • Flooded Type Evaporator: Tubes are immersed in refrigerant, which surrounds the tubes. Used in high-capacity systems for better heat transfer.
  • Falling Film Evaporator: Refrigerant is sprayed as a thin film over the tubes, enhancing heat transfer efficiency.