Data center lower air supply system and data center machine room

The utility model provides a data center lower air supply system and a data center machine room, and belongs to the technical field of data center refrigeration, the data center lower air supply system comprises a floor plenum chamber, a refrigeration part and a supplementary refrigeration part, the floor plenum chamber is provided with an air inlet and an air outlet, and the air outlet is arranged on the top surface of the floor plenum chamber; the refrigerating piece is connected with an air inlet of the floor plenum chamber; and the supplementary refrigerating part is used for ventilating air to the air inlet of the floor plenum chamber and the tail end of the floor plenum chamber through an air supply pipeline. According to the data center lower air supply system provided by the utility model, cold air enters the machine room for refrigeration after passing through the air outlet, and the supplementary refrigeration piece ventilates to the air inlet of the floor plenum chamber and the tail end of the floo