I claim the ornamental design for a refrigeratable air chiller for a fan, as shown and described.
FIG. 1 is a perspective view of a refrigeratable air chiller for a fan showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof, the left side elevational view being a mirror image thereof; and,
FIG. 5 is a perspective view showing the refrigeratable air chiller for a fan in use; the phantom lines depict environmental structure for illustrative purposes only and form no part of the claimed design.