Advances in heat transfer herald a new dawn for plant temperature control
The design and installation of efficient temperature control within plant systems has been subject to a lack of innovation for decades, and plant managers and installers have long-suffered a dearth of choice.
Ammonia has been used as a primary refrigerant in industrial applications for more than 150 years. It is the go-to refrigerant in many applications, including food processing and storage, building services and process applications.
Although environmentally sound, the hazards and acute toxicity associated with ammonia mean the safe design and operation of refrigeration systems is paramount.
The dangers of its use are pulled sharply into focus when something goes wrong, and the death of a plant worker at a UK brewery following a leak in 2016 only serves to underline this.
It’s no different when it comes to secondary refrigerant systems. For decades plant managers have had one hand tied behind their backs as they are forced to choose a fluid that is either non-toxic but gives poor performance or one that offers enhanced performance but is toxic. So it could be argued that industrial temperature control is overdue a step change and that process engineers deserve better.
Chemists who study the flow of liquids have been working hard behind the scenes to innovate. They have set their sights firmly on secondary refrigerants and the results are paying off. New developments promise to not only end the toxicity-versus-efficiency dilemma once and for all, but also herald potential new options for industry for the first time in a century and a half.
The current status quo offers four choices of heat transfer fluids for secondary refrigeration.
* Mono-ethylene glycol (MEG)-based heat transfer fluids are used in cooling systems as they offer good physical properties, but 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) – has a more favourable toxic profile 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 another alternative but brings with it a high flame risk. When used with pressurised ammonia, the results of a leak or incident could represent an explosive combination.
* A fourth - salt brines - performs well but has proved to be corrosive to pipework and systems.
Scientists at Kilfrost, a UK-based firm recognised as a pioneer of safety-critical anti- and de-icing fluids for the aviation industry, took on this challenge two-and-a-half years ago.
Technical manager, Michael Reynolds, says that he and his team had responded to industry feedback that highlighted the need for a new solution, and explains how they have been working behind the scenes to bring their expertise to bear on heat transfer.
“Plant managers simply don’t have choice, they don’t have options. And it’s been this way for decades. We went into the lab and worked tirelessly to come up with something that would for once provide a viable alternative to what’s currently out there.
“We knew we had to make a fluid that was non-toxic and more efficient than current fluids. So we formulated it with organic, approved inhibitors and viscosity modifiers. We developed it to reduce pressure drops across the system, as well as to reduce pumping costs and increase hydraulic efficiency.”
Sucess in the field
Reynolds says that the results of testing the advanced low viscosity (ALV) Plus fluid were impressive. “It has been shown to be 66% less viscous than MPG and offer 35% energy savings. It has an operational temperature down to -40°C and so outperforms MEG, MPG, Bio-PDO and ethanol-based heat transfer fluids. It's also been approved by the NSF as safe for incidental food and beverage contact. We were pleased, but needed to see ALV Plus in operation out in the field to truly understand the potential benefits to industry.”
Reynolds and his team took the new solution to Canadian energy management consultant I.B. Storey, which 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 US$14,000 per year through a saving of 39% of pump operating costs. Due to a reduction in fluid viscosity of 15%, capital costs were also reduced, representing construction cost savings of over US$17,500.”
He adds: “We’ve been absolutely delighted with the early response from companies globally using our heat transfer fluids, which for the first time ever have been told that they can have both efficiency and non-toxicity, and can use it with their legacy systems.”
The ALV Plus fluid is part of a range of ALV fluids produced by Kilfrost to suit different industries and applications. Data from external tests on the performance of the fluids is being submitted to OEM simulators, allowing them to demonstrate the efficiency and performance benefits as well as evaluate the use of smaller hardware.
Once results are returned, Reynolds says that Kilfrost 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.
“Market prohibitions on CFCs and increasingly HFCs have meant industry has been encouraged to turn back to ammonia for primary refrigerant, despite its inherent dangers and an opportunity to innovate and seek something less toxic. I understand that ammonia is efficient, and environmentally sound, but as a chemist starting out on an experiment, my first thought is whether the substance is toxic - if it is, I immediately ask myself if it has to be used at all and if so, is there a substitute?
“Our results could show resulting benefits for the primary refrigerant setup in terms of efficiency and equipment installations, but maybe they will moreover herald a new dawn for heat transfer and temperature control altogether. Heaven knows we’ve waited long enough.”
Brewery embraces new solution
With energy costs spiralling, the brewing industry has long been seeking a cost-effective, efficient and safe alternative to current heat transfer fluids.
But for decades breweries have had one hand tied behind their backs as they are forced to choose a fluid that is either non-toxic or one that offers enhanced performance. However, when the scientists at Kilfrost launched ALV Plus, this dilemma was solved.
In a recent case study, the operators of Pillars Brewery, a craft lager producer based in London, were looking for the most efficient glycol product for use in cooling the brewery’s fermentation tanks. But the brewery also needed a less viscous product than that which is generally used in brewing to crash cool its beer more quickly. Doing this means not only a reduction in electricity costs but means the brewery can stay true to its values by having a smaller carbon footprint, keeping innovation and quality at the heart of what they stand for. For these reasons, Pillars turned to the ALV Plus fluid.
Brewer and Pillars founder, Gavin Litton, says: “Thanks to Kilfrost ALV Plus, our pumps are working less hard and using less energy to circulate liquids around the plant. We’ve been so impressed with the performance of the fluid, as it not only saves us money, but also means we’re as energy-efficient and environmentally friendly as possible. That’s at the heart of what we stand for as a brewery.”