An enclosure forms a plurality of tiers vertically stacked in a longitudinal dimension. Each tier is a 1U modular computer system having a computer chassis configured for mounting in the multi-tiered support, and computer components that need cooling within the computer chassis. A cold plate is in thermal communication with at least one of the computer components, and convectively removes heat from that component using a liquid coolant. A heat exchanger dissipates heat from the liquid coolant, and provides liquid coolant back to the cold plate. An air mover within the chassis cools the heat exchanger, blows air across other components needing cooling, and removes heated air from the chassis. The air mover may extend substantially across the chassis, or it may blow crosswise from an outlet-ventilating direction.