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Innovation in heat transfer fluids

24 January 2020

Advances in heat transfer herald a new dawn for efficient and cost-effective temperature control in refrigeration systems. Food Processing reports. 

Traditionally, when it comes to heat transfer fluids, there has always been a need to compromise – By either specifying a fluid that is toxic but which offers energy efficiency benefits or one that has poorer performance.

Further, the design and installation of efficient refrigeration systems has been subject to a lack of innovation and many would argue that industrial temperature control is overdue a step change.

Now, thanks to the hard work behind the scenes of chemists who study the flow of liquids, results are paying off.

A new development promises to end the toxicity-versus-efficiency dilemma and also herald potential new options and cost savings for industries that rely on refrigeration systems – such as the food industry. Currently, the status quo offers four choices of heat transfer fluids for secondary refrigeration.

• Mono-ethylene glycol (MEG)-based heat transfer fluids primarily offer good physical properties and efficiency. But they are avoided as they are toxic, and so pose a risk to human health if there is incidental contact with items intended for human consumption.
• The preferred alternative by many – mono-propylene glycol (MPG) – is safer, but is far less efficient at transferring heat energy, particularly at low circulation temperatures. Plant managers are stuck with managing risk, or removing risk and removing performance.
• Ethanol is alternative used by some, but it is not particularly efficient and its low flash point brings a flammability risk.
• A fourth – salt brines – perform well but are corrosive to pipework and systems.

Over two years ago scientists at Kilfrost took on the challenge to find a better solution. Dr Michael Reynolds, technical manager at Kilfrost, explains: “We were responding to industry feedback that highlighted the need for a new cost-effective solution. For decades, food, vegetable and fruit retailers whose chiller cabinets and freezers currently consume huge amounts of electrical energy simply don’t have choice, they don’t have an alternative. We went into the lab and worked to come up with something that would provide a viable alternative to what’s currently out there, and money for end-users.

“We knew we had to make a fluid that was non-toxic and more energy efficient than current fluids. So we formulated it with NSF-approved organic acid technology inhibitors. We developed it to reduce the incidence of pressure drops across the system. It was essential to reduce pumping costs and increase hydraulic efficiency.”

The results of testing the resulting Advanced Low Viscosity (ALV) Plus fluid showed it to be 66% less viscous than MPG and it offers a 35% in energy savings. It has an operational temperature down to -40°C and outperforms MEG, MPG, Bio-PDO and ethanol-based heat transfer fluids. Crucially, the fluid has also been approved by the NSF as safe for incidental food and beverage contact.

“We were pleased with the ALV Plus test results,” continued Reynolds, “but we needed to see it in operation out in the field to truly understand the potential benefits to industry. We took it to Canadian energy management consultants I.B. Storey, who had been asked by a chocolate manufacturer in Ontario to review its plant’s energy efficiency.”

After trialling ALV Plus, results identified potential electricity savings of over $14,000 per year through a saving of 39% of pump operating costs. Due to a reduction in fluid viscosity, capital costs could be reduced by 15%, representing construction cost savings of over $17,500.

Potential applications
Given its non-toxic profile and low viscosity, the fluid is expected to have many potential applications within the food and beverage sectors – including large food storage facilities, where control over the warehouse temperature is beneficial to preserving fruits and vegetables.

The brewing and beverage sector across the UK, USA and Europe has also responded favourably, witnessing the energy savings and environmental benefits of using a more efficient fluid.

Data from external tests on the performance of the fluids will soon be submitted to OEM simulators, allowing Kilfrost to demonstrate the efficiency and performance benefits as well as evaluate the use of smaller heat exchangers and compressors.

“Once results are returned, we would expect to see that due to the efficiency of the ALV range, there may be an opportunity to review primary refrigeration system set ups, and early indications suggest a positive effect,” said Reynolds. “Our results could show benefits for both the primary and secondary refrigerant setup in terms of efficiency and equipment installations, but maybe they will also herald a new dawn for heat transfer and temperature control altogether.”


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