Ground-Air heat exchanger system for controlled ventilation
'Ever improving insulation and the air tight construction of buildings means that controlled ventilation is becoming ever more important. The ground to air heat exchanger makes a considerable contribution to this, especially when used in conjunction with an air heat exchanger unit. As well as increasing the quality of life within the building, this also provides significant energy cost reductions by using the embodied ground energy to pre-condition the incoming ventilation air. So, on the one hand, heating costs can be saved, whilst on the other, the air conditioning system investment costs can also fall, especially in larger buildings.
The ground to air heat exchanger takes advantage of the fact that the temperature of the ground, 1.5 to 2m deep, remains a relative constant temperature between 7ºC-12°C summer and winter alike. The incoming outside air passes through an underground pipe system to heat it in winter and to cool it in summer. Experience shows that a ground to air heat exchanger makes it possible to raise the temperature of air taken in by up to 9°C in winter, and to reduce it by up to 14°C in summer.
• Reduction of heating costs by pre-heating air in winter
• Pleasant cooling effect in summer, reduces need for air-conditioning
• Improvement of the air quality in the building through dust and pollen filters
• No build up of microbes inside the pipe system due to silver pipe lining
• PP material with improved heat conductivity ensures optimal heat transfer
• High longitudinal rigidity for safe condensation removal
• Individual design with the REHAU bespoke design software
• Reduced need to open windows
The pipe is made of polypropylene and comes complete with an integrated antimicrobial layer, made of silver particles. This prevents microbial growth on the inside of the pipe, which would otherwise cause musty smells. The air inlet also has a dust and pollen filter, a further benefit to allergy sufferers. The PP material also has excellent heat transfer properties and is simple to install by a groundworks contractor.
For a domestic application, a single 40m loop of pipe around the house is normally sufficient for the demands, whereas for a commercial project, a Tichelmann grid system is used with header pipes of diameters up to 1200mm. The Tichelmann layout is a selfbalancing system (whichever path the air flows through the system, it always travels the same distance) reducing any pressure losses.
In both cases, it is normal for the 200 OD or 250 OD Awadukt Thermo pipe to be used for the heat transfer. The pipes are laid a metre apart in the existing soil and require a gradient of 2% to the condensation discharge, which builds up when the air is cooled in the summer.'