If those are the dimensions of the VIEWABLE AREA, then it definitely won't fit. You're gonna need to add to that the non-viewable areas of the tube and the mounting brackets.
FWIW, the overall dimensions of the tube and mounting brackets on my 27" monitor are ~24" w x 22.75" h. If you stripped off some of the bracketing and got creative, you could get the height down to about 19.5".
Presumably the required dimensions should be similar, if not identical for the guts of a 27" TV.