Irrigation of a raised bed

Raised beds do get drier than non-raised, but not that much drier if you've added lots or organic matter to the soil first.

I'd suggest you put the pipe about 5cm below the soil and if it's a slow system, then allow about 8 hrs/week of run so that the water slowly seeps down to the bottom roots. This is a superior way to water all plants, and being a bit under the soil you protect the pipe from any  degeneration by UV rays and evaporation. It's easily moved as you fluff up the beds next year.
It its a fast run system, then try to slow it down so the soil can absorb it.

I neglected to mention that the 8 hour run of water should be all at one time - this gives the most benefit rather than lots of shallow waterings which causes more plant stress than benefit.