I recently bought a window air conditioner and opened the case to inspect the fan as recommended by the instructions. I am interested in how they work and have been reading about it. My question is, why don't any of the copper pipes have insulation on them? I understand the purpose of the heat exchangers and generally how everything works, but could the copper piping that the refrigerant travels through work better if it were insulated? This includes the capillary tube. Also, the two halves (indoor and outdoor part) are only separated by a fairly thin piece of plastic. Would the efficiency be better if this had some kind of better insulation as well? It has a pretty good efficiency rating (10.7) for a window unit, so maybe that kind of stuff just doesn't make much of a difference. Any thoughts?

Usually window units are designed for the lower price market especially today since most are not made in the USA. Cost is probably why your unit is the way it is. It is not worth the time and effort to insulate/modify the window A/C system. Plug it in and enjoy the cool air.