Heat recovery with hybrid ventilation in office buildings

Abstract

This master thesis examines the possibilities of creating a decentralized hybrid ventilation system with a heat recovery system. Natural ventilation is more commonly used as the main ventilation principle and has the advantage to lower the energy costs of a building. One of the downsides of the natural ventilation system is the lack of heat recovery. By combining the heat recovery abilities of a decentralized mechanical ventilation system with driving forces of natural ventilation, a new decentralized ventilation system is created. This ventilation system will be located at a typical 70’s office building in the Netherlands. The main boundary condition for a natural ventilation system is the driving force. This can be buoyancy or a wind induced principle. The wind induced ventilation principle generates the largest pressures and velocities in comparison with buoyancy based ventilation. The wind direction will have a large influence on the wind velocity at the façade. Average wind velocities of 2.4 m/s are measured during simulations for wind perpendicular to the façade. In the simulation, the manual heat load calculations are used for the input. These simulations showed that by using two ventilation systems per office, each having a capacity of 50 m3/h, will meet the requirements of 100 m3/h of fresh air for the office. The Fiwihex system used for the heat exchangers will recover enough heat in order to reduce the need for additional heating to almost zero. The final design consists of an integraded box in the façade. This box will have a wind cowl inlet and a venture shaped outlet at the outside of the façade in order to generate a sufficient air flow. Due to the small size of the box, 150x300x1200mm (d x w x h), its location on the façade can vary. The system can be used in an enclosed office area as well as an open plan office. Due to the high efficiency of the heat exchanger and the use of wind as a driving force, energy savings of 5% of the total energy use of the building and even higher can be achieved.