Why Semi-Welded Plate Heat Exchangers Are Used in Ammonia Refrigeration

Ammonia (NH₃) is one of the most efficient and environmentally friendly natural refrigerants. It offers excellent thermodynamic performance, zero global warming potential (GWP), and high energy efficiency. For this reason, ammonia is widely used in industrial refrigeration systems such as cold storage, food processing, chemical plants, and ice rinks.

However, ammonia is also toxic, corrosive to certain materials, and operates under relatively high pressure, which places strict requirements on heat exchanger design.

This is where Semi-Welded Plate Heat Exchangers (SWPHE) become the optimal solution.

Key Reasons for Using Semi-Welded Plate Heat Exchangers

1. Safety: Ammonia Must Never Mix with Water

In ammonia refrigeration systems, one side of the heat exchanger carries ammonia, while the other side carries water or glycol.

Semi-welded design ensures:

• Ammonia channels are fully welded (no gasket contact)

• No risk of refrigerant leakage into water system

• Maximum operational safety

This is a fundamental requirement in ammonia system engineering.

2. High Pressure Capability

Ammonia systems typically operate at:

• Condenser pressure: 10–18 bar

• Evaporator pressure: 2–6 bar

Semi-welded plate heat exchangers can handle:

• Design pressures up to 25–30 bar

• Repeated pressure fluctuations

• Thermal cycling without gasket fatigue

This makes them far more reliable than fully gasketed designs.

3. Excellent Heat Transfer Efficiency

Compared with shell-and-tube heat exchangers:

• Plate heat exchangers provide 3–5 times higher heat transfer coefficients

• Smaller approach temperature (1–3 K)

• Lower refrigerant charge

• Compact footprint

This directly reduces:

• Compressor power consumption

• System energy cost

• Equipment installation space

4. Maintenance: One Side Welded, One Side Serviceable

The unique advantage of semi-welded design:

This allows:

• Safe isolation of ammonia

• Easy mechanical cleaning of water side

• No need to open refrigerant circuit during maintenance

Which is extremely important for food and cold storage facilities.

5. Material Compatibility

Semi-welded plate heat exchangers typically use:

• Stainless steel 316L or 304 for plates

• Laser or TIG welded ammonia channels

• Special elastomers for water side gaskets

This ensures:

• Long-term corrosion resistance

• Compliance with food and safety standards

Engineering Conclusion

In ammonia refrigeration systems, semi-welded plate heat exchangers provide the ideal balance between:

• Safety

• Efficiency

• Pressure resistance

• Maintainability

They combine the thermal performance of plate heat exchangers with the safety of welded structures.

This is why semi-welded plate heat exchangers have become the industry standard solution for industrial ammonia refrigeration.