A condenser, also known as a liquefier, is a key component in high-temperature heat pumps for industrial applications. Its primary function is to convert gaseous working fluids, previously compressed in the compressor, into a liquid state by releasing heat to an external medium.

Operating principle of a condenser:

1. Superheated vapor inflow: After compression in the compressor, the hot, high-pressure refrigerant gas enters the condenser.
2. Heat release: In the condenser, the refrigerant transfers its heat to another medium, often water or air. This heat transfer occurs via heat exchangers, such as plate heat exchangers, which enable efficient energy exchange. In a steam heat pump, the condenser simultaneously acts as the steam generator.
3. Condensation: As the refrigerant releases heat, its temperature drops, causing it to transition from a gaseous to a liquid state.
4. Liquid transport: The now-liquid refrigerant is directed forward, with an expansion valve reducing the pressure, before reabsorbing heat in the evaporator, restarting the cycle.

Additionally, in a subcooler, the still-hot condensate can be utilized to preheat the medium at the heat sink.

Precise matching and design of the condenser, refrigerant, and process maximize the heat pump’s efficiency.

Material and design

In industrial applications where high-temperature heat pumps supply process heat, the condenser is crucial for the overall system’s efficiency. It must be capable of transferring large amounts of heat at high temperatures without compromising the refrigerant’s thermodynamic properties. The choice of material and condenser design is therefore critical:

• Material: Corrosion-resistant materials such as stainless steel or special alloys are commonly used for high-temperature applications to ensure long service life.
• Design: Shell-and-tube or plate heat exchangers are the most common designs, as they allow for efficient heat transfer while maintaining a compact structure.

Application in high-temperature industrial heat pumps:

High-temperature heat pumps are key to the decarbonization of industrial applications, particularly in providing process heat at temperatures up to and above 200°C—such as for drying or sterilization processes in the food industry or distillation processes in the chemical and pharmaceutical industries. Here, the steam generated by the heat pump is further compressed to higher temperatures using a mechanical vapor recompressor. The condenser efficiently transfers the heat generated in this compression process to the medium to be heated, playing a crucial role in industrial energy efficiency.