The ornamental design for a circulartubularframe for a desk fan, as shown and described.
FIG. 1 is a front perspective view of the circular tubular frame for a desk fan of the present invention;
FIG. 2 is a rear perspective view showing the circular tubular frame for a desk fan of the present invention;
FIG. 3 is a front elevational view of the circular tubular frame for a desk fan;
FIG. 4 is a rear elevational view of the circular tubular frame for a desk fan;
FIG. 5 is a side elevational view of the circular tubular frame for a desk fan;
FIG. 6 is a side elevational view of the opposed side of the circular tubular frame for a desk fan;
FIG. 7 is a bottom view of the circular tubular frame for a desk fan; and,
FIG. 8 is a top view of the circular tubular frame for a desk fan.
The broken line showing of the fan grill, hub and base is included for the purpose of illustrating environmental structure and forms no part of the claimed design.