IEC 62610-6:2020 pdf download-Mechanical structures for electrical and electronic equipment – Thermal management for cabinets in accordance with IEC 60297 and IEC 60917 series.
5 Determination of recirculation and bypass ratio 5.1 Cooling airflow in a cabinet Figure 1 schematically shows the airflow in the cabinet in which the subrack is mounted, with arrows by size and direction according to the flow balance. In the equipment cabinet, cooling air is supplied from the front, enters from the inlet of the subrack into the interior, cools the interior of the subrack, exhausts from the subrack, and is exhausted from the rear of the cabinet. A part of the cabinet intake bypasses the subrack and is directly exhausted to the outside of the cabinet without passing through the subrack. A part of the subrack exhaust air is recirculated, returning to the subrack intake and not exhausting outside the cabinet.
6.4.5 Intake air temperature of a cabinet The intake air temperature of a cabinet T Ri is measured at three points in the upper, middle, and lower parts of the intake face of the cabinet, the distance from the face is 50 mm to 200 mm away, and the average value of the three points is taken as the measurement value. If the cabinet is configured as a cold aisle containment, the temperature at a position representing the cold aisle may be used. And, if the cabinet is installed in an indoor open space, the temperature at a position representing the room temperature may be used. 6.4.6 Exhaust air temperature of a cabinet The exhaust air temperature of a cabinet T Ro is measured at three points in the upper, middle, and lower parts of the exhaust face of the cabinet, the distance from the face is 1 0 mm to 30 mm away, and the average value of the three points is taken as the measurement value. If the cabinet is configured as a hot aisle containment, the temperature at a position representing the hot aisle may be used.