Plate Heat Exchanger for Multistack Air-Cooled Chillers

A plate heat exchanger (PHE) is a critical component in Multistack air-cooled chiller systems, where compact design, high thermal efficiency, and reliable performance are essential. In these chillers, plate heat exchangers are commonly used as evaporators, condensers, or intermediate heat exchangers to optimize heat transfer between refrigerant and water or glycol circuits.

Compared with traditional shell-and-tube designs, plate heat exchangers offer higher efficiency, reduced refrigerant charge, and a significantly smaller footprint—key advantages for modular Multistack chiller installations.

Role of Plate Heat Exchangers in Multistack Air-Cooled Chillers

In a Multistack air-cooled chiller, the plate heat exchanger typically serves one or more of the following functions:

• Refrigerant-to-Water Evaporator – Chilled water or glycol is cooled by refrigerant evaporation inside the plates

• Refrigerant-to-Water Condenser (in specific configurations)

• Free Cooling or Heat Recovery Heat Exchanger – Transfers heat between process loops without compressor operation

Its compact construction aligns well with Multistack’s modular and space-efficient design philosophy.

How the Plate Heat Exchanger Works

A plate heat exchanger consists of multiple thin, corrugated metal plates stacked together. The working principle is as follows:

1. Alternating Flow Channels
   Refrigerant flows through one set of channels, while water or glycol flows through the adjacent channels.

2. Large Heat Transfer Surface Area
   The corrugated plates create turbulence even at low flow velocities, dramatically increasing heat transfer efficiency.

3. Efficient Thermal Exchange
   Heat is transferred through the plate walls with minimal temperature difference (low approach temperature).

4. Rapid Response
   Small internal volume allows fast system response to load changes—ideal for variable cooling demands.

Key Advantages for Multistack Chillers

1. High Heat Transfer Efficiency

• Up to 3–5 times higher heat transfer coefficient than shell-and-tube exchangers

• Lower approach temperature improves overall chiller COP

2. Compact and Lightweight Design

• Ideal for modular Multistack units

• Reduced mechanical room space requirements

3. Reduced Refrigerant Charge

• Small internal volume minimizes refrigerant quantity

• Supports compliance with environmental regulations

4. Flexible Capacity Control

• Plate count can be adjusted to match exact load requirements

• Suitable for staged or modular chiller configurations

5. Easy Integration with Glycol Systems

• Compatible with ethylene glycol and propylene glycol mixtures

• Common in low-temperature and free-cooling applications

Typical Materials and Construction

Plate heat exchangers for Multistack air-cooled chillers are commonly manufactured with:

• Plates:

• AISI 316 stainless steel (standard)

• Titanium (for corrosive fluids, optional)

• Gaskets:

• EPDM (chilled water, glycol)

• NBR (refrigerant compatibility)

• Brazed or Gasketed Designs:

• Brazed Plate Heat Exchangers (BPHE): Compact, no gaskets, widely used in chillers

• Gasketed Plate Heat Exchangers: Serviceable and expandable designs for larger capacities

Applications in Multistack Air-Cooled Chiller Systems

Plate heat exchangers are widely used in:

• Commercial HVAC chilled water systems

• Data center cooling with redundancy requirements

• Industrial process cooling

• District cooling plants

• Free cooling and heat recovery systems

Their modular nature perfectly complements Multistack’s scalable chiller architecture.

Design and Selection Considerations

When selecting a plate heat exchanger for a Multistack air-cooled chiller, the following parameters are critical:

• Cooling capacity (kW or tons)

• Chilled water or glycol flow rate

• Inlet and outlet temperatures

• Refrigerant type (R134a, R407C, R410A, R454B, etc.)

• Maximum operating pressure and temperature

• Fouling factor and water quality

Proper sizing ensures stable operation, high efficiency, and long service life.

Maintenance and Reliability

Plate heat exchangers offer excellent reliability when properly designed and maintained:

• Smooth plate surfaces reduce fouling

• High turbulence minimizes scaling

• Gasketed units allow easy inspection and cleaning

• Brazed units offer leak-free, long-term operation

Routine water quality control further extends service life.

Conclusion

A plate heat exchanger is an ideal heat transfer solution for Multistack air-cooled chillers, delivering superior efficiency, compact size, and system flexibility. Whether used as an evaporator, condenser, or heat recovery component, PHEs enhance chiller performance while supporting modular design and energy-efficient operation.