Heat Loss for a Run-Around Hybrid Ventilation System with Heat Recovery

The heat recovery system for ventilation is of major importance when low energy buildings are built. One alternative to the mechanical ventilation systems with heat recovery is to use a brine based run-around system that allows for heat recovery in for instance hybrid ventilated buildings. This type of heat recovery system has the potential to lower the need for electricity for the fans. Also, the installation has the potential to be simpler when pipes transporting the brine replace traditional air ducts. However, pipes needed to transport the brine will suffer from thermal losses. This will lower the efficiency of the heat recovery system. High losses could in practice make the system unusable. In order to estimate how much this affects the annual heat recovery a simulation tool was developed using TRNSYS. The result from the investigation shows that the losses for a system with 40 m pipes in total are approximately 300 kWh annually. This corresponds to approximately 9% of the energy savings from the ventilation heat recovery system. Insulating the pipes can reduce this heat loss by approximately 250 kWh annually