Primary air treatment vs energy saving: comparison between different design solutions

In civil application the most diffuse type of HVAC is the mixed one made by fancoils and primary air system. Usually the primary air has not only the aim of replace the exhaust air in the rooms. During the cooling season air plants have the task of dehumidification of the indoor air which is humidified by the indoor humidity sources, like the human skin transpiration and breathing of the people. On the other hand, during the heating period the fresh air must be humidified to compensate the low humidity ratio of the external air. With the aim of energy saving related to the ventilation in buildings, from the beginning 2018 the new European Regulation EU 1253/2014 has been introduced some limits in terms of energy efficiencies. The present work investigates different layouts of plants for the primary air treatment in HVAC systems. Several types of heat recovery units have been considered in the study in order to find which is the best solution for the optimization of the air treatment. Several case studies have been considered in the energy analysis and the results obtained through numerical simulations have highlighted the critical nature of the interventions aimed at limiting energy consumption in primary air treatment systems. (paper)