Cooling structure of electronic equipment rack

A cooling structure of an electronic equipment rack comprising a plurality of shelf units in a vertically stacked tier, each shelf unit having generally vertical side wall surfaces and upper and lower, generally horizontal surfaces and accommodating therein a plurality of printed circuit boards with the major planar surfaces thereof oriented in a vertical direction, each of the generally horizontal surfaces having vent holes therein to enable a cooling airflow to pass in a generally vertical direction through the shelf unit, the cooling structure comprising;

• plural fan units, each fan unit comprising spaced, generally vertical side wall portions having vent holes therein and at least one fan mounted therein and oriented to produce a flow of air in a generally vertical, upward direction and for introducing ambient air from the exterior of the side wall portions in a generally lateral direction through the vent holes and combining same in additive relationship to the generally upward vertical airflow above the fan;
• each fan unit being disposed on the top surface of an associated shelf unit in the electronic equipment rack and defining, with the associated shelf unit, a corresponding cooling block providing a cooling airflow passing in the generally vertical direction through the vent holes of the associated shelf unit and the fan unit;
• and
• the successive cooling blocks producing a cooling airflow of gradually increasing flow rate in the upward vertical direction from the lowermost shelf unit to the uppermost shelf unit in accordance with the respective, successive fan units thereof and the additive, ambient airflows respectively introduced by the successive fan units.