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Quotes - Engineering - SalesGlycol & Secondary Loops
Secondary Refrigeration Interfaces
Secondary loops circulate glycol or brine between the refrigeration plant and the process, so the primary refrigerant stays in one place.
The approach penalty. Every exchanger between the refrigerant and the process consumes temperature difference. Keeping that penalty small is what makes a secondary loop viable, and it is where a plate pack earns its place.
Glycol properties. Thicker than water, worse at conducting heat, and holding less of it per degree — and every one of those three moves the wrong way as the loop gets colder. The exchanger must be sized on the actual fluid at the actual temperature.
Concentration discipline. Every point of glycol above the freeze protection requirement costs heat transfer and pumping power. Set it to what is needed and monitor it, because it drifts with make-up.
Typical Specification
- Loop fluid: Glycol, brine or other secondary refrigerant
- Purpose: Keeps primary refrigerant charge confined
- Cost: Additional temperature approach
- Sizing basis: Actual fluid properties at operating temperature
- Concentration: Minimum required for freeze protection
- Viscosity: Rises sharply as temperature falls
- Interface: Plate exchanger between primary and secondary
- Materials: Stainless standard
- Alternative: Falling film chiller where cold water suffices
- Monitoring: Glycol concentration checked periodically
Common FAQs
To keep the primary refrigerant charge small and confined to the plant room, which simplifies safety, regulation and leak management. The cost is an extra temperature approach and a fluid that is harder to pump.
Substantially, and more as it gets colder. Higher viscosity, lower conductivity and lower specific heat all work against you at once, and the exchanger must be sized on the actual fluid rather than on water.
Sometimes. Where the process needs cold water rather than glycol, a falling film chiller makes near-freezing water directly and removes both the loop and its approach penalty.
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