A thermal management surface system comprises a substantially flat sheet and a plurality of support members. The sheet has a plurality of open funnel-like channels therethrough with a larger upper opening and a smaller, spout-like lower opening. The support members lie on a support surface in a spaced-apart arrangement with the sheet resting on the support members substantially parallel to and offset vertically above the support surface; the support surface and the sheet thereby define a containment space. Each of the spout-like lower openings is canted to impart lateral momentum on gas flowing into the upper opening and out of the lower opening. Groups of multiple contiguous channels can have spout-like lower openings canted substantially along a common direction, so that gas flowing out of those lower openings flows along the common direction through the containment space.