depends on the machine and case design, but leaving it open can actually impede the air flow and - counterintuitively - hinder coolng
PCs depend very much on a directional air flow, in through one vent, over the CPU/GP, then out via another. On older machines the PSU was the exit, newer ones via a rear vent. The actual internal routing depends on whether the system is ATX, mATX or BTX. But it all boils down to one thing - on a properly designed system taking the side panel off can actually make the machine run hotter
I notice in that photo that there appears to be no exhaust fan, and the CPU fan isn't ducted to the outside, so in your case, taking the side panel off may help.
As for those copper heatpipes - I think you'll find they're solid copper
Last edited by Milo Minderbinder; 27th Aug 2012 at 21:24.