MODULE
129
PROUDLY SPONSORED BY
REFRIGERATION 2020
Skills summary
CORROSION AND ASSET PROTECTION
■ What? A guide to the impacts of corrosion on HVAC&R equipment and strategies to prevent it.
■ Who? Relevant for mechanical contractors, consultants, engineers, building designers, sustainability/energy efficiency advisers, facility managers and building owners.
Corrosion is a huge contributor to unnecessary energy and efficiency loss. It will cause a loss in cooling performance, reduced indoor air quality, reduced reliability, reduced energy efficiency and a reduction in service life. These issues will cause such things as discomfort and health risks to building occupiers, higher running costs, higher capital costs and more CO2. But there are ways to limit or prevent this corrosion from occurring. This Skills Workshop provides a step-by-step explanation and analysis of how HVAC&R equipment is affected by corrosion in heat exchanger coils. It looks at how this impacts on efficiency and how it can be prevented in new units or stopped in existing units.
According to the CSIRO, HVAC systems in buildings account for approximately 40–50 per cent of building energy use and contribute to 34.7 megatonnes of carbon dioxide emissions every year. With electricity prices continuing to rise per year and with building energy contributing to Australia’s greenhouse gas emissions, HVAC&R energy efficiency is a major economic and environmental issue, even when not considering the increase in building construction and the expansion of building footprints that we currently see in Australia.
Heat exchanger geometry Air-cooled heat exchangers consist of fins mounted on tubes to expand the heat-exchanging surface. Tubes and fins can be made of several metals like steel, copper, aluminium and stainless steel.
Louvred fins
The heat exchangers, also called coils, may have various dimensions depending on the application. Most heat exchangers are made of copper tubes and aluminium fins. This is because aluminium is easy to process, light and relatively corrosion resistant. Coil manufacturers use different fin forms to adjust the coil to the demands. The simplest form is the straight fin, a flat fin with only minor waves. More complicated is the louvred fin. This fin is perforated to create turbulence of air in the coil. This will increase the capacity of the coil. A coil with this fin type will be much more vulnerable because of the thin aluminium louvres. The louvred fins have an air filtering effect and will be exposed to more pollution. Another option for creating more heat exchange capacity is a wavy fin. The waves will force the air to bounce against the aluminium. See Figure 1.
Straight fins
Wavy fins
Figure 1 March 2020
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www.airah.org.au/nation
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HVAC&R Nation
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