The ornamental design for a bubblepromoter for a cross-flow tray, as shown and described.
FIG. 1 is a top perspective view of a bubble promoter for a cross-flow tray showing our new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a rear elevation view thereof;
FIG. 6 is a front elevation view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken line representation of a portion of a cross-flow tray in FIG. 5 is for purposes of illustration only and forms no part of the claimed design.