Professor Sam Luxton had never looked inside an induction air conditioning unit before - but within three weeks he co-designed a system that uses 30 per cent less power.

FOR Professor Sam Luxton and former PhD student Vladimir Petrovic, it's been a case of being in the right place at the right time. In 1994 the pair were called to investigate an air conditioning problem in a 13-storey CBD office building, owned by Adelaide University. The solution they came up with in just three weeks has led to them being co-owners of a $3 million-a-year business today.

With turnover doubling annually, their company, Dadanco Pty Ltd, has installed air conditioning equipment throughout Australia and in the UK, the US, Singapore, Sri Lanka, India and New Zealand. They are currently working on two of New York's best-known buildings, and there is potential for the technology to be adopted much more widely still, because of its ability to cut power bills by 30 per cent while at the same time dramatically reducing noise levels.

The basis of the two men's success is their deduction that some relatively minor changes in the shape of the air outlets can bring about major improvements in the performance of 'induction' air conditioning systems, so called because they cool or heat air by inducing it to flow past a heat exchanger (a zig-zag grille of copper piping with chilled or heated water pumped through it from a central plant).

"To be absolutely honest I'd never seen an induction air conditioning system until I was asked by the University to go and have a look," Professor Luxton, who has now retired as Professor of Mechanical Engineering, said. "I'd been researching turbulence and mixing and jets for 40 years and I'd seen sketches of induction systems and shown them in lectures, but I'd never physically seen one. "The University was losing its tenants in the building at the rate of knots, because the air conditioning was too noisy and not coping with the heat load."

"When I had a look I thought 'you know, I wouldn't start from here if I was going to design one of these'. "But we were locked into finding a quick, cheap solution based on what was already there, and I knew that what we had to do was increase the amount of entrainment (the gathering up of surrounding fluid by a jet when it leaves a nozzle). I knew that more entrainment would lower the noise levels. "One of the ingredients that went into the solution was remembering that the very first Boeing 707s were banned from London airport because of their noise. "To reduce this problem, the Boeing designers put a series of eight large petals on the jet nozzle. "The petals resulted in more air being entrained by the jet exhaust after it left the engine." Professor Luxton explained that this increased entrainment of air reduced the jet velocity, which reduced noise dramatically.

The relevant law of physics is that noise varies with the velocity raised to the power of eight. "Because we were dealing with much smaller quantities of air and lower velocities we had to use a somewhat different design, but it only took us three iterations to get the solution," he said. "We increased the entrainment ratio (the ratio of the air drawn into the unit relative to the air discharged through the jets) from around two to somewhere between four and six. "It was all done in the acoustic laboratories at the University, in a matter of a few weeks." The next step was to have the new-shaped nozzles made up by an Adelaide plastics injection moulding company, and then to refit the building.

"We had the jets made so that they were flexible and could be slipped into the existing holes, then we paid a team of 13 postgraduate students for a weekend's work to refit the building." As well as the plastic nozzles, the refurbishment kits used by the students to retrofit the building's 557 ceiling-mounted units comprised a clip-on piece of bent sheet metal that changed the shape of the mixing chamber. This also acted to reduce internal pressure and so increase the flow of air through the heat exchanger.

"We had the jets made so that they were flexible and could be slipped into the existing holes, then we paid a team of 13 postgraduate students for a weekend's work to refit the building." As well as the plastic nozzles, the refurbishment kits used by the students to retrofit the building's 557 ceiling-mounted units comprised a clip-on piece of bent sheet metal that changed the shape of the mixing chamber. This also acted to reduce internal pressure and so increase the flow of air through the heat exchanger.

The results were close to what Professor Luxton and Mr Petrovic expected: around 5-10 decibels cut in noise and an increase of more than 30 per cent in efficiency. The 'quick fix' contributed to the building being almost fully tenanted again, but it was not an isolated case - the same problems are being experienced in thousands of other buildings world wide.

This is due to a combination of stricter regulations concerning noise and temperature, and the failure of induction air conditioning systems installed during the 1960s and 1970s to cope with the dramatically increased heat loads in buildings brought about by electonic office equipment such as computers, printers, fax machines and photocopiers - and the loss of 'masking' noise from the click-clack of typewriters.

The two researchers realised that they had valuable intellectual property on their hands, and for most of the following year attempted to negotiate a licence for the technology with a large building services company. They were just about to sign an agreement when that company was taken over by another company, and they decided that the best course was to go it alone. Their company established a design and manufacturing facility in the Adelaide suburb of Thebarton, and has now moved into its origin in the 'Capita' building. Its technology has won many scientific and business awards and been granted international patents.

	refurbishment, or the fitting of new nozzles and side walls to existing induction units;
	retrofit, or the replacement of entire existing systems throughout a building with new Dadanco units; and
	custom-designed systems for new buildings.

Among refurbishment projects have been Australia Square and Walsh Bay wharf in Sydney, 360 Collins Street and 385 Bourke Street in Melbourne, MLC Building and Queensland Rail Centre in Brisbane, the Capita building in Perth, United World College in Singapore, National Mutual building in Auckland, and the heritage-listed headquarters of Boots the Chemist in Nottingham, UK.

Refurbishment kits have been developed for all the major induction air conditioning brands, including Carrier, Barber-Coleman, Environ, Sinki-Dunn Air, Trane, Velovent, Worthington and York. Earnings from such projects have enabled the company to 'pull itself up by the bootstraps' to its current $2-3 million turnover.

Early development was assisted by funding from Adelaide University and a Commonwealth Government R&D Start grant, which Professor Luxton said was instrumental in obtaining definitive data. "Without that early support we wouldn't have made it," he said. "Apart from mortgages there have been no capital inputs.

"It's been a constant struggle to keep the bank happy, but thank heavens the bank now sees us as a reliable risk and are being much more supportive." Growth in previous years was at a breakneck 300-500 per cent per annum, but this year has slowed considerably to 'only' 100 per cent in the aftermath of the Asian financial crisis. "We started off just a little bit early in our export marketing and stretched ourselves just a little bit too far," Professor Luxton said. "We opened an office in Singapore in 1998 and did eight successful projects, but the Asian crisis knocked us and we couldn't keep that office going."

For new buildings, Dadanco has produced software that can help architects to simulate an air conditioning system and position outlets in the best locations. The higher efficiency of Dadanco systems means they use much smaller ducts, which in turn means a saving of 30cm of ceiling space on every floor of a building. In a large building, this allows another floor of lettable space for every 12 floors within the normal height limit, as well as reducing air conditioning maintenance and running costs and saving a large amount of plant room space.

With more than a quarter of the greenhouse gas emissions from any city's CBD coming from air conditioning, Dadanco's 30-40 per cent energy saving offers scope for big greenhouse gas reductions. "Making the whole system less expensive is the key to getting people to reduce greenhouse gas emissions," Professor Luxton said. "The sooner we stop exporting inefficient equipment to developing countries the better - the rate of air conditioning growth around the Pacific rim is frightening."