An air-cooling apparatus is provided which includes an air-cooling wall cooling airflow passing through an electronics rack(s) of a data center. The air-cooling wall is disposed separate from and in spaced relation to the air inlet or air outlet side(s) of the electronics rack(s), and includes a wall panel support structure disposed separate from the electronics rack(s), which supports one or more slidable wall panels. The slidable wall panel(s) includes an air-to-liquid heat exchanger slidably supported and disposed in spaced relation to the air outlet or air inlet side of the electronics rack(s). The heat exchanger extracts heat from air passing across the heat exchanger and is slidable within the support structure in a direction transverse to the direction of airflow through the rack(s). Slidable support of the heat exchanger by the support structure facilitates access to the air outlet or air inlet sides of the electronics rack(s).