Secondary Refrigerants Are Worth A Second Look
All refrigeration systems, at their very core, convert electrical energy into heat removal potential. Primary refrigerants typically do this via the refrigeration cycle of compressing, condensing, expanding and evaporating. Secondary refrigerants typically transfer heat from place to place without changing phase. Volatile secondary refrigerants are the exception to this rule but are rarely used and therefore will be excluded from discussion for now. Most refrigeration discussions focus on the primary refrigeration cycle and the primary refrigerant. This blog entry seeks to make secondary refrigerants the primary topic for a change.
Why Use A Secondary Refrigerant?
Secondary refrigerants can have many appealing traits, but they always come at increased cost. Additional pumps, piping, and tanks all have additional capital cost and electrical cost, but often the benefits outweigh the costs. Using a secondary cooling loop such as chill water, glycol, brine, or similar product can lower the risk of leaks into the air or product as well as lower the refrigerant charge. This may increase employee safety, reduce food safety concerns, and potentially save thousands of dollars in product someday. Many facilities may see a benefit in reducing refrigerant charge to lessen Process Safety Management (PSM) requirements as well.
What Secondary Refrigerant Is Right for Me?
Choosing a secondary refrigerant can be difficult, there are many options and in Carlson & Stewart Refrigeration’s opinion there isn’t a clear frontrunner. Choosing what’s best for your facility is worth a second thought. Evaluating the optimal temperature and food safety requirements of your facility are a great place to start. Below I’ve shown a quick look at the various options, with the understanding that a one or two sentences likely doesn’t do any of them justice.
Common Secondary Refrigerants
- Chill Water – Simple and inexpensive, with drawbacks due to freezing and potential for bacterial growth and scale build up.
- Brine Water – Relatively simple and inexpensive with lower temperature potential than water, but corrosive nature is hard on equipment.
- Propylene Glycol – Better freezing temperatures and growth inhibitors than water and brine, but comes at an increased cost, reduced heat transfer capabilities, and eventually “freezing”.
- Ethylene Glycol – Similar to Propylene with better heat transfer performance due to lower viscosity. High toxicity makes it less appealing for many food production applications.
- Ammonia Water – Better freeze point than chill water with some beneficial properties but currently is rarely used in refrigeration applications due to toxicity.
- Hybrids – Many companies have made proprietary thermal fluids, often with many of the beneficial characteristics of several refrigerants listed above. Limited suppliers, cost, and uncertainty about the blend’s future may make them unappealing.
As always, Carlson and Stewart Refrigeration would be happy to help walkthrough the design and install of your next refrigeration project!