Secondary refrigerants strike back
With the F-gas Regulation's stringent demands on fluorinated refrigerant leakage control, the use of secondary refrigerants such as ethylene glycol is coming into vogue. Recently, when opening a new Mexican food factory, Discovery Foods, a British family-owned ethnic food-manufacturing business, asked cooling specialist Coolmation to design an unusual food application that would provide both chilled water to mix with a dough product and chilled air to blast cool tortillas when removed from the oven. The project included a 250 kW Rhoss air cooled glycol chiller. Using secondary refrigerants such as glycol has several advantages: only a small amount of refrigerant is held in each circuit, which limits harmful potential risks of leakage and allows the system to remain operative in the case of multi-circuits. Gas leaks from chillers are easier to locate as they only happen in the confines of the chiller rather on the long pipe runs found in direct-expansion systems. Chilled glycol systems generally hold 90% less refrigerant than direct expansion systems and the risk of harmful refrigerant leakage is restricted to the machine room, sparing the food production area. Chilled glycol also has the advantage of not being a blend: in blends, the various fluids evaporate at different rates in cases of leakage, obliging the blend to be replaced. Glycol systems can also be factory-assembled and tested whereas direct-expansion systems which have to be assembled on site. Only the leak testing of the outdoor chiller is compulsory in secondary refrigerant systems, which are also more flexible and are easy to replace. The modular approach this allows was one of the reasons secondary systems were chosen for this project. The primary refrigerant used here was R-407C.