An evaporator is a heat exchanger designed to absorb heat from a surrounding environment or fluid by evaporating a liquid refrigerant (or process fluid) inside it. This process of absorbing latent heat of vaporization provides a powerful cooling effect.
1. Refrigeration and Air Conditioning (HVAC&R)
This is the most common application, where the evaporator is the component that produces the desired cooling.
- Refrigerators and Freezers:
- Application: The evaporator coil is located inside the insulated compartment.
- Why? Liquid refrigerant inside the coil evaporates, absorbing heat from the inside air and keeping the food cold.
- Home and Commercial Air Conditioners:
- Application: The evaporator coil is part of the indoor unit (air handler).
- Why? Warm room air is blown over the cold coil. The refrigerant inside evaporates, absorbing heat from the air and cooling it down before it is circulated back into the room.
- Automotive Air Conditioning:
- Application: A small evaporator core is located inside the dashboard.
- Why? It cools and dehumidifies the air before it is blown into the vehicle’s cabin.
2. Industrial Process and Chemical Engineering
Evaporators are used to separate mixtures and concentrate solutions.
- Concentration:
- Application: Removing water from a solution to concentrate the desired product.
- Examples:
- Food & Beverage: Concentrating fruit juices, milk (before drying into powder), sugar syrup, and coffee extract.
- Chemicals: Concentrating acids, salts, and polymers.
- Desalination:
- Application: In multi-stage flash (MSF) or multi-effect distillation (MED) plants, evaporators are used to boil and evaporate seawater.
- Why? The vapor is then condensed to produce fresh, potable water, leaving the salts behind.
- Waste Treatment:
- Application: Concentrating industrial wastewater or effluent.
- Why? To reduce the volume of waste for disposal and to recover valuable chemicals or water for reuse.
3. Heat Pumps
A heat pump is essentially an air conditioner that can run in reverse. The evaporator’s role changes based on the mode.
- In Heating Mode:
- Application: The evaporator coil is located outside (in the air or ground).
- Why? It acts as a “cold” sink, absorbing ambient heat from the outside air or ground. The refrigerant evaporates, carrying this thermal energy inside to be released by the condenser.
4. Chillers
Chillers are machines that remove heat from a liquid (typically water or a water-glycol mixture) via a refrigeration cycle.
- Application: The evaporator is where the chilled liquid is cooled.
- Why? The cold liquid is then pumped to distant locations to cool air (in air handlers) or process equipment. This is used in:
- Large building air conditioning
- Cooling industrial processes (e.g., plastic moulding, laser cutting, MRI machines)
District cooling systems