Fluid delivery techniques with improved reliability

Techniques for improving reliability of print cartridges (50) that employ a fluid recirculation path (61). One reliability feature is provided by active heat management, wherein the recirculation path is employed to provide printhead cooling. Another feature is an in-printer printhead and standpipe priming technique. Idle time tolerance can also be improved, with the ability to re-circulate ink and purge air, to provide a mode of operation that can improve the reliability of the print cartridge during idle times. A Acleaning fluid@ can be introduced that could breakup the sludge as it circulates through the print cartridge. Improved particle filtering is provided, through fluid recirculating through the system, passing through the standpipe or plenum area (94) and across the backside of the printhead (92). As the fluid moves through this region, particles trapped in the standpipe get swept out of the area and eventually through a filter before reaching the printhead again