Channeling follows the burst rules for AoE. So there needs to be an unbroken line of effect between the channeler and the person to be healed. An open door on its own would not block a channel, but positioning might.
..........0
_____..........______
..........0
In the above extremely crude diagram, a channel energy used by either 0 would hit the other.
.......0
______...______
...0
In this second case, there is a broken line of effect, and so a Channel used by either 0 would not hit the other 0.
"Channeling energy causes a burst"
"A burst spell affects whatever it catches in its area, including creatures that you can't see. It can't affect creatures with total cover from its point of origin (in other words, its effects don't extend around corners). The default shape for a burst effect is a sphere, but some burst spells are specifically described as cone-shaped. A burst's area defines how far from the point of origin the spell's effect extends"
Core Rule Book Excerpts.
Keep in mind when it says "ones you cant see" mean invisible or hidden, not ones not in 'line of sight'.
Basically, you need line of effect.
Line of Effect: A line of effect is a straight, unblocked path that indicates what a spell can affect. A line of effect is canceled by a solid barrier. It's like line of sight for ranged weapons, except that it's not blocked by fog, darkness, and other factors that limit normal sight.
You must have a clear line of effect to any target that you cast a spell on or to any space in which you wish to create an effect. You must have a clear line of effect to the point of origin of any spell you cast.
A burst, cone, cylinder, or emanation spell affects only an area, creature, or object to which it has line of effect from its origin (a spherical burst's center point, a cone-shaped burst's starting point, a cylinder's circle, or an emanation's point of origin).
An otherwise solid barrier with a hole of at least 1 square foot through it does not block a spell's line of effect. Such an opening means that the 5-foot length of wall containing the hole is no longer considered a barrier for purposes of a spell's line of effect.