radiator flow: connecting IN and OUT lines, yay or nay?
 

please consider the illustration attached.

i am expanding my radiator system for two new ADJACENT radiators that will be on their own new branch out of the network and both radiators have shutoff valves so the flow in and out of the radiator is a variable. is it necessary to connect the radiator IN line (the same as boiler OUT line) and OUT (same as boiler IN) outside the radiators to ensure that there always is flow no matter whether the radiators valves are on or off?

i was thinking this might be necessary to make sure other radiators on the system that are not turned off do get uninterrupted flow.

please let me know if this question doesn't make sense.

thanks

Almost makes sense. Are you using zone valves and thermostats in this system?

Almost? LOL. of course i use a central thermostat. dunno what a zone valve is.