A film fill-pack (12) has a plurality of fill-sheets (14,50,52,58,60) with an ordered array of ridges (163) and grooves (165) generally extending above a planar surface on both the obverse and reverse surfaces of a fill-sheet, which fill-sheets at an assembled state provide the ridges and grooves of facing obverse and reverse surfaces of adjacent fill-sheets in an arrangement providing a plurality of channels (220,222) between adjacent fill-sheets for gas flow therethrough and where the ordered arrangement of ridges (163) and grooves (165) induces spiraling of the gas flow through the channels (220,222) for promotion of improved heat transfer; and, where the fill-sheets (14,50,52,58,160) further include a spacing arrangement (252) providing a compact nesting of adjacent sheets with minimal sheet-to-sheet displacement at least at two of the edges for compact handling, transfer and storage with a self-spacing of adjacent fill-sheets at assembly of the film fill-pack. Fill-packs generally utilize retention louvers (16,455) at a gas-inlet site to maintain coolant fluid within the fill-pack structure, which disclosed louvers have specific relationships to their angularity, height and length to minimize their volume while maintaining their operational characteristics, and mist eliminators (28) at air discharge locations are operable to minimize gas-entrained coolant discharge to retain the fluid within the cooling apparatus with the control of the angles of mist-eliminator grooves, the structural cross-section of the grooves and the use of microgrooves.