New chiller looks to bring ammonia cooling to mainstream

Gateshead specialist KGM Refrigeration has designed a chiller that it believes will enable more widespread use of ammonia refrigerant, which as well as being highly energy efficient, offers a GWP of zero.

The AMChill packaged chiller runs on what is described as an ultra-low charge of ammonia, made possible by a new design that overcomes the need for the conventional flooded evaporator.  The chiller based on open-drive Bitzer W-series compressors optimised for use with ammonia, is designed for roof-top mounting so doesn’t the extensive risk mitigation measures, such as high capacity exhaust ventilation, required in plant room applications.

The chiller’s light weight and compact dimensions (1m wide by 1.6m long and 1.9m high) enable it to be easily transported onto rooftops without the use of a crane via a standard lift, saving installation time and cost, the firm says.

Amar Marwaha, Engineering Director at KGM Refrigeration, said:

Traditionally, ammonia’s downsides are obviously toxicity and flammability. However, we went back to the drawing board to develop a new chiller design that dramatically reduces the charge required for a given duty, while retaining the efficiency and environmental benefits. From a thermodynamic perspective, ammonia is the most efficient refrigerant available, delivering very high energy efficiency and low running costs. As a natural refrigerant, its environmental credentials are also impeccable.

The key to the new design is the charge reduction: by working with very low superheat, which maximises efficiency, together with a reduced volume of pipework, the ammonia charge can be reduced by around 75%. For example, for a duty of 150 kW, the charge would be just 10 kg on the KGM chiller.

The chiller features integrated ATEX-rated leak detection with system shutdown and an ATEX-rated fan for enclosure ventilation. The chiller is available in three sizes, 100kW to 150kW (based on an outlet temperature of +6 deg C), and is ideal for use in pharmaceutical and industrial process cooling, cold stores, plastics manufacturing and for cooling industrial machine tools, the firm says.

The chiller has had its world debut at Sterling Pharma Solutions in Cramlington, Northumberland. Here a 150kW AMChill provides supplementary cooling for existing process refrigeration plant. The pilot is part of a wider environmental programme by Sterling aimed at achieving carbon neutral status for the site. Other initiatives include the completion of a new anaerobic digestion plant to create methane gas from waste solvents, which is then converted into energy and injected into the national grid, and a combined heat and power (CHP) plant to generate the site’s own electricity.

Amar said:

The cooling load at the test site is highly variable, and provided excellent validation of the chiller’s ability to respond rapidly to changes in demand. To date, the unit has over 5,000 run hours, and has performed to design since being commissioned.

Brian Peutherer, Vice President of Environment, Health and Safety at Sterling, added:

Sterling was delighted to participate in the pilot trial, as innovative technology fits directly into our business model, and this was a great opportunity to apply it to our sustainability drive. We have set ourselves challenging environmental goals to become carbon neutral and achieve best-in-class energy, sustainability and waste management practices across our operations. Refrigeration is a key element. With zero global warming potential and zero ozone depletion potential, plus excellent efficiency, ammonia cooling systems are highly sustainable and future-proof against F-gas changes.

Brian noted that the rooftop design ensures that potential risks are minimised. The company is now installing further AMChill chillers at the site, and extending the roll-out to other production facilities.

One of the keys to the chiller’s efficiency is the use of a variable speed drive linked to a synchronous reluctance IE5 motor, which believed to be the first refrigeration application in the UK. When linked to Bitzer’s reciprocating compressor, it can modulate speed and enable output to be precisely matched to cooling load, delivering, an improvement of around 10% against conventional chillers running on synthetic refrigerants.

A heat pump version of the chiller is also available to enable recovery of waste heat, which would further boosting overall efficiency levels. KGM says it is now working on reducing the ammonia charge by refining the design and minimising pipe lengths, which it believes could yield an additional 20% reduction – to around 8kg for a 150kW unit.

The firm says that for building owners, the chiller’s higher capital cost will be more than offset by its extended working life (between 20-25 years) and lower energy costs, reducing the lifetime cost of ownership, compared with standard chillers.

For installers, the benefits include compactness, ease of handling on site, and a packaged design that requires only water and electrical connections, making it ‘plug and play’.

Kevin Glass, Managing Director of Bitzer UK, added:

We as an industry, and indeed the world in general, face some difficult decisions in the light of the recently revised F-gas regulation. Rooftop-mounted, ultra-low charge packaged ammonia chillers offer some compelling benefits and could well find application in mainstream applications currently served by global warming synthetic refrigerants.