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The energy efficiency and energy consumption of mechanical ventilation systems depend mainly on the heat and cool recovery efficiency and the operational costs of electric energy for air handling unit fans.
For free pre-heating of fresh air in winter and pre-cooling in summer and to protect the heat exchanger in the air handling unit against freezing earth-to-air heat exchangers (EAHEs) are used. For large demand of fresh air multi-pipe systems are used to diminish total pressure losses and provide required amount of thermal energy.
Total pressure losses in EAHEs and consequently the specific fan power (SFP) depends on their geometrical parameters such as: the length, diameter and number of parallel pipes, angle of connection parallel pipes to the main pipes and main pipes diameter. In this paper an influence of the angle of connection between main and parallel pipes (45 and 90 degrees) on the SFP factor and energy demand for ventilation system operation was investigated using experimentally obtained total pressure losses of EAHEs models. Results are shown in graphical form. Quite significant influence of the investigated angle of connection on the fan power, and on the SFP value is presented.