Electric Warm Air Heating - replacing ducting

[lxbn]

I have an electric warm air central heating system in my apartment. The unit is situated in the kitchen. The boxed in duct supplying warm air to the bedroom runs along the bottom of the length of one wall in the kitchen.
I am re-modelling the kitchen and the size of the boxed in duct (16x44cm) gets in the way of a sensible positioning of appliances - not to mention having to cut out large sections in the back of the floor units. I haven't opened the boxing yet, but I reckon that it may contain a round duct inside - the system is quite a few years old but works well.
I have looked around for a replacement flat ducting but the only ones I have found are made from PVC. This would be exactly right, except that I’m not comfortable using this material in a heating system. I’m not sure how hot the warm air gets but over time the duct may not cope too well.
I could take out the heating system but as the apartment block is not supplied with gas, the option is to have electric panel heaters and I’m not sure if this is a good idea.
Does anyone know if there is anyone who supplies similar flat ducts in metal or can I just use a round flexible aluminium and squash it down to fit.

 

[simond]

The duct work is probably steel rectangular. PVC would not be a good idea.

However the biggest flaw in your plan revolves around the fact that the duct would have been sized for a particular air resistance; by the sound of it you wish to make it smaller or add more bends; you will upset the system balance.