Nichrome Wire No Heating with 9V
A really good 9V battery can supply a few watts and might have an available specification that would give better guidance to designing your heater. If the wire is too long, too little current will be allowed to flow and the wire won't produce very much heat. If it's too short, then too much current will flow, and the battery will heat up more than the wire. If you have a multimeter, you should ensure the output of the battery is near 9V and see if the current through the wire is near 1A. If memory serves that's close to the optimum you will see from a 9V.