Potassium Formate Secondary Cooling System: Design, Performance, and Selection Guide

A potassium formate secondary cooling system uses an aqueous potassium formate solution to transport cooling from a primary refrigeration plant to cold rooms, industrial equipment, process heat exchangers or other cooling loads.

Instead of circulating the primary refrigerant throughout the entire facility, the refrigeration plant cools a secondary potassium formate fluid, which is then pumped through a separate closed-loop system.

ASHRAE defines secondary coolants as liquids cooled by a refrigerant and used to transfer heat without changing phase. These fluids are also commonly called heat-transfer fluids, brines or secondary refrigerants.

How Does a Potassium Formate Secondary Cooling System Work?

A simplified system can be represented as:

Primary refrigeration plant → heat exchanger → potassium formate loop → cooling load → return loop

The system normally includes:

• Chiller or primary refrigeration plant
• Plate or shell-and-tube heat exchanger
• Potassium formate coolant
• Circulation pumps
• Insulated piping
• Valves and controls
• Expansion tank
• Air coolers or process heat exchangers
• Monitoring equipment

The potassium formate solution absorbs heat at the cooling load and returns to the refrigeration plant, where it is cooled again.

Primary vs Secondary Cooling

Factor	Primary Refrigeration	Potassium Formate Secondary System
Main fluid	Primary refrigerant	Potassium formate solution
Compressor cycle	Yes	No
Phase change	Normally yes	Normally no
Main role	Generate refrigeration	Transport cooling
Distribution	Refrigerant piping	Pumped liquid loop

This distinction is important.

Potassium formate normally does not replace the primary refrigerant itself. Instead, it reduces the need to distribute that refrigerant throughout the complete facility.

Why Use Potassium Formate?

Low-Temperature Freeze Protection

Water has excellent heat-transfer properties but freezes near 0°C.

Potassium formate dissolved in water lowers the freezing or crystallization temperature, allowing the secondary loop to operate below the freezing point of pure water.

ASHRAE recommends choosing a secondary coolant whose freezing point is at least about 3 K below, and preferably around 8 K below, the lowest temperature the coolant will experience.

Therefore, concentration should be designed around the actual minimum system temperature.

Relatively Low Viscosity

Viscosity is especially important in secondary systems because the coolant must be pumped continuously.

Higher viscosity means:

• Higher pressure drop
• Greater pump power
• Lower flow for a given pump
• Potentially larger piping
• Changes in heat-transfer performance

Published research on aqueous potassium formate as a secondary refrigerant found significantly lower viscosity than traditional aqueous alcohol and glycol solutions under the studied conditions. The authors found that the lower viscosity helped keep pumping-power requirements competitive even though volumetric heat capacity was lower.

Thermal Conductivity and Heat Transfer

The same research reported good thermal conductivity for potassium formate solutions, supporting effective heat transfer in indirect refrigeration systems.

However, system designers should consider several properties together:

• Viscosity
• Thermal conductivity
• Specific heat
• Density
• Flow rate
• Temperature difference

A secondary coolant should never be selected based only on freezing point.

Where Are Potassium Formate Secondary Cooling Systems Used?

Cold Storage

A central refrigeration plant can distribute chilled potassium formate fluid to multiple:

• Freezer rooms
• Chilled warehouses
• Distribution zones

Food Processing

Secondary cooling may serve:

• Processing rooms
• Production equipment
• Cold rooms
• Heat exchangers

Industrial Process Cooling

Applications can include:

• Manufacturing equipment
• Chemical processes
• Process vessels
• Industrial heat exchangers
• Temperature-controlled production

Refrigerated Logistics

Large logistics facilities may use centralized secondary loops to cool multiple refrigerated zones.

Ice Rinks

Secondary coolant can circulate through pipe networks below the ice surface.

ASHRAE notes that secondary coolant systems have extensive refrigeration applications, including food processing and ice-rink systems.

Potassium Formate 75% as System Feedstock

Vanchor currently supplies Potassium Formate 75% Solution as a concentrated raw material for selected secondary refrigeration and heat-transfer fluids.

Its current guidance lists potential applications including:

• Cold-storage warehouses
• Food-processing plants
• Industrial cooling systems
• Ice rinks
• Refrigerated logistics
• Process-temperature control
• Low-temperature circulation systems.

A nominal 75% solution contains approximately:

750 kg potassium formate per metric ton of solution.

The concentrate can be pumped, metered and diluted without requiring solid potassium formate dissolution.

Why 75% Is Not Automatically the Working Concentration

A secondary cooling system should not simply use the highest potassium formate concentration available.

Changing concentration affects:

• Freeze/crystallization temperature
• Viscosity
• Density
• Specific heat
• Thermal conductivity
• Pumping requirements

Vanchor specifically notes that concentrated potassium formate may be diluted to achieve the required freezing point, viscosity and heat-transfer performance.

A better design sequence is:

Minimum operating temperature → freeze-protection margin → concentration → thermal properties → hydraulic calculations

Potassium Formate vs Glycol Secondary Systems

Ethylene glycol and propylene glycol are more common secondary coolants, while ASHRAE identifies potassium formate as a less widely used alternative.

Factor	Potassium Formate	Glycol
Chemistry	Aqueous formate salt	Aqueous glycol
Sub-zero use	Yes	Yes
Low-temp viscosity	Relatively low in published comparison	Can rise substantially
Thermal conductivity	Favorable	Concentration-dependent
Pumping	Can be attractive	Strongly viscosity-dependent
Corrosion protection	May be required	Usually required

Research comparing potassium formate with alcohol/glycol systems identified good thermodynamic properties, low toxicity, non-flammability, lower viscosity and good thermal conductivity as useful characteristics.

This does not mean potassium formate is universally better than glycol.

Total system performance must be compared.

Pump Selection and Pressure Drop

Pump sizing is one of the most important parts of secondary cooling-system design.

Engineers should calculate:

• Fluid flow rate
• Pipe length
• Pipe diameter
• Fittings
• Heat exchanger pressure drop
• Minimum-temperature viscosity
• Pump efficiency

ASHRAE notes that viscosity directly affects pressure drop and that secondary coolant system design must consider pumping energy as part of overall system performance.

Using room-temperature viscosity values for a sub-zero system can result in incorrect pump sizing.

Corrosion and Material Compatibility

A secondary cooling system may contain:

• Carbon steel
• Stainless steel
• Copper
• Brass
• Aluminum
• Pumps
• Valves
• Gaskets
• Elastomers

ASHRAE states that secondary coolants should be compatible with all system materials at the actual temperatures and pressures encountered.

Vanchor also recommends evaluating the complete potassium formate formulation for:

• Corrosion
• Pump compatibility
• Seal compatibility
• Crystallization temperature
• Storage stability
• Long-term concentration stability.

Corrosion inhibitors may therefore be required.

Chloride and Raw-Material Purity

Potassium formate is not a chloride salt, but industrial grades may contain trace chloride impurities.

For long-life cooling systems, buyers may specify:

• Potassium formate assay
• Maximum chloride
• Iron
• Insoluble matter
• pH
• Density

These parameters should be confirmed through a batch-specific COA.

Water Quality for Dilution

Dilution water becomes part of the secondary cooling fluid.

Poor water quality may introduce:

• Chloride
• Calcium
• Magnesium
• Iron
• Suspended solids

Possible consequences include:

• Corrosion
• Scale
• Deposits
• Heat-exchanger fouling

The final diluted fluid should therefore be checked before the system is commissioned.

Concentrate Storage vs System Operating Temperature

Do not confuse the two.

A concentrated Potassium Formate 75% raw material can have different crystallization behavior from the final diluted working coolant.

Vanchor's current product information recommends keeping the 75% concentrate above approximately 10°C and preventing crystallization during storage.

Once diluted to the engineered working concentration, the coolant has a different crystallization profile.

Important System Design Parameters

Before designing a potassium formate secondary cooling system, evaluate:

1. Minimum coolant temperature
2. Required freeze-protection margin
3. Potassium formate working concentration
4. Crystallization temperature
5. Viscosity at minimum temperature
6. Density
7. Specific heat
8. Thermal conductivity
9. Required flow rate
10. Pumping power
11. System metallurgy
12. Corrosion-control requirements

These parameters should be evaluated as one system rather than individually.

What Buyers Should Request

When sourcing potassium formate for a secondary cooling project, request:

• Product specification
• Concentration
• Density with test temperature
• pH
• Chloride specification
• Iron and insoluble matter
• COA
• TDS
• SDS
• Storage guidance
• Packaging information

Also provide:

Minimum operating temperature
Cooling application
Target working concentration
System metallurgy
Required volume
Packaging
Destination

Potassium Formate for Secondary Cooling From Vanchor

Vanchor currently supplies Potassium Formate 75% Solution to refrigeration-fluid and heat-transfer-fluid formulators.

Its current product page specifically identifies potential applications including:

• Industrial refrigeration
• Cold storage
• Food-processing refrigeration
• HVAC secondary circuits
• Process cooling
• Low-temperature circulation systems.

The concentrate provides convenient pumping, metering and dilution, while the final secondary coolant formulation should be engineered for the actual system.

Frequently Asked Questions

What is a potassium formate secondary cooling system?

It is an indirect cooling system that uses a pumped aqueous potassium formate solution to transport cooling from the primary refrigeration plant to the cooling load.

Is potassium formate a primary refrigerant?

Normally no. It generally acts as the circulating secondary coolant.

Why use a secondary cooling system?

It allows cooling to be distributed through a pumped liquid circuit instead of circulating the primary refrigerant throughout the entire facility.

Can Potassium Formate 75% be used directly?

Not necessarily. It is typically used as concentrated feedstock and diluted to achieve the required freezing point, viscosity and thermal performance.

Can potassium formate replace glycol?

It can be considered as an alternative in selected systems. Engineers should compare viscosity, heat-transfer properties, pumping energy, corrosion, materials and lifecycle cost.

What is the most important design parameter?

There is no single parameter. Minimum temperature, concentration, viscosity, thermal properties, pump performance and material compatibility must be evaluated together.

Conclusion

A potassium formate secondary cooling system uses a liquid secondary loop to distribute cooling efficiently across:

Cold-storage facilities
Food-processing plants
Industrial refrigeration systems
Process cooling equipment
Refrigerated logistics
HVAC secondary circuits

Potassium formate offers useful sub-zero performance, relatively low viscosity and good thermal conductivity, making it a technically interesting secondary coolant.

Successful system design still requires careful control of working concentration, crystallization temperature, fluid properties, pumping energy, heat-exchanger performance, corrosion and material compatibility.

For system formulation, Potassium Formate 75% Solution can serve as concentrated feedstock that is diluted and conditioned according to the actual secondary cooling-system requirements.