This kind of Virtual Sensor is largely applied in different fields. In automotive. Air Mass Meters are used for for determining the air aspirated by the internal combustion engine. In the Oil & Gas companies the Multiphase Flow Meters are expensive and difficult to install and maintain. In this case the Virtual flow Meters can be used both to continuously check the health status of the physical devices or to replace or integrate the physical sensors in flow assurance applications. In buildings and industrial plants the Virtual Flow meters are used to estimate the coolant flow in HVAC systems, ventilation airflow and compressed air leakages. We provide reliable algorithms for Virtual Flow Metering based on Ensembles of NARMAX models and Deep Neural Networks.