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.

FAQ – Semi-Welded Plate Heat Exchangers in Ammonia Refrigeration

1. Why can’t fully gasketed plate heat exchangers be used with ammonia?

Ammonia (NH₃) can attack certain gasket materials and poses serious safety risks if leakage occurs.

In fully gasketed plate heat exchangers, both sides rely on elastomer sealing. If gasket degradation happens, ammonia could leak into the water circuit or to atmosphere.

Semi-welded designs eliminate this risk by fully welding the ammonia channels.

2. Why not use fully welded plate heat exchangers instead?

Fully welded plate heat exchangers offer high safety, but they are:

• More expensive

• Difficult to mechanically clean

• Less serviceable on fouling water side

Semi-welded plate heat exchangers provide the optimal compromise:
Welded refrigerant side + serviceable water side.

3. Are semi-welded plate heat exchangers suitable for ammonia evaporators and condensers?

Yes. They are commonly used as:

• Flooded ammonia evaporators

• Ammonia condensers

• Ammonia subcoolers

• Cascade intercoolers

Their pressure resistance and safety design make them ideal for these applications.

4. What design pressure can semi-welded plate heat exchangers handle?

Typical design pressures range from:

• 16–25 bar standard

• Up to 30 bar or higher depending on manufacturer

They are specifically engineered to handle ammonia pressure fluctuations and thermal cycling.

5. Is refrigerant charge lower compared to shell-and-tube heat exchangers?

Yes.

Semi-welded plate heat exchangers typically require significantly lower ammonia charge compared to shell-and-tube designs, which:

• Improves safety

• Reduces refrigerant inventory

• Lowers regulatory burden

This is a major advantage in modern industrial refrigeration plants.

6. Can the water side be cleaned?

Yes.

The water (or glycol) side is gasketed and removable, allowing:

• Mechanical cleaning

• Plate inspection

• Replacement of gaskets

The ammonia circuit remains sealed during maintenance.

7. What materials are recommended for ammonia applications?

Common materials include:

• Stainless steel 316L plates

• Laser or TIG welded ammonia channels

• NBR or EPDM gaskets (on water side only)

Material selection must comply with pressure and corrosion requirements.

8. How does efficiency compare with shell-and-tube heat exchangers?

Semi-welded plate heat exchangers typically provide:

• 3–5 times higher heat transfer coefficients

• Smaller approach temperature (1–3 K)

• More compact installation

This results in improved COP and lower compressor power consumption.

9. Are semi-welded heat exchangers suitable for CO₂ systems as well?

No. pressure can not reach  high pressure. have to choose Utra high pressure plate heat exchanger

10. Why are semi-welded plate heat exchangers considered the industry standard in ammonia refrigeration?

Because they provide the optimal balance between:

• Maximum safety (welded ammonia channels)

• High thermal efficiency (plate design)

• Pressure resistance

• Serviceability

• Reduced refrigerant charge

This combination makes them superior to both fully gasketed and traditional shell-and-tube designs in ammonia systems.