Temperature and airflow setting in dual-duct ventilation systems

Abstract

Past experiences of excess energy consumption and malfunctioning controls introduced prejudice when considering dual-duct ventilation systems during design stages. Modern technologies, however, can be used to improve performance and control of dual-duct systems, thus making these a sensible and safe design option. In the paper, we discuss challenges associated with setting the warm and cold supply air temperatures and how these set-points affect the airflows. We present limitations in temperature settings, due to instantaneous room thermal conditions and the individual design temperature requirements. Portions of warm and cold air (the ratio of these in the ventilating airflow) affect the transport costs of ventilating airflow. In many cases, rational control of warm and cold air temperature set-points, in a yearly cycle, enables distribution of similar portions of warm and cold air within the system. Even airflows in warm and cold air installations minimise the overall flow resistance, so that the air transport costs are minimal. Simultaneously, apart from minimising the energy for air transport, the primary energy demand for air treatment should be controlled and minimised.