So here are 2 easy quick-fixes to keep your too hot apartment cooler, while at the same time passing on the extra warmth to your chillier neighbors below you.  This approach also increases our building energy efficiency.

FROST KING F17X Fiberglass Cover for 3" Pipes, Pre-Slit1.  Install fiberglass pipe insulation.  I got some at the Home Depot for less than $10 per 3 ft.  You can get it in different styles, but the easiest is the self-sealing tubes that just snap over your pipes (see pic).  For aesthetics, it is already a paper white outside, but I bought the steel air duct pipes and snapped it overtop for a little industrial look in the kitchen.   Be sure to know your pipe diameter before you go.  I learned the hard way and bought 2.5″ diameter insulation, when I only needed the 1.5″! See Google product search results here

Magnetic Vent Covers (8" X 15")2. Install magnetic vent covers. You can buy these (3 for $10!) at Bed, Bath and Beyond.  Just cut them to fit your radiators.  See Google product search results here