A study of energy exchange in earth air tubes

Abstract: As energy issues today are of great interest the writers of this report have done a research about an alternative to save energy by reducing the cost of preheating the outdoor air. By taking the outdoor air to the ventilation system via a pipe buried in the ground, you can preheat the outdoor air, which, in turn, could save energy. By doing this you do not have to bring as much energy to preheat the supply air, to get the desired supply air temperature. The report also explains if the earth air tubes are a good complement to the mechanical ventilation system with a heat exchanger. The report begins with describing briefly the history of ventilation systems in use today. It also describes the functions of the system and show to the reader how two of the installation layouts looks like. The writers using the project Daggkåpan in Linköping as a basis for the investigation and they also provide an alternative solution to the existing ventilation system. This report also demonstrate the factors that come into play to get as much energy exchange as possible, and what problems may arise with this type of complement to the ventilation system with a heat exchanger. Trough optimization of the earth air tubes and depending on which energy source is in use, you can actually save energy and by that also money. The factor that proved to bethe most significant for the energy exchange was the pipe length. Other factors such as trench depth, pipe diameter and the air flow has been shown to play a smaller role in how much energy you can save. Finally the report ends with the writers own reflections and a discussion based on the results.