A combustor having U-shaped cooling channels is disclosed. The combustor may include a shell having an impingement hole, a liner spaced from the shell and having an effusion hole; a first partition spanning between the shell and the liner, a second partition spaced from the first partition and spanning between the shell and the liner; and a U-shaped channel defined between the shell and the liner and defined in part by the wall, the channel having upstream and downstream ends both adjacent the first partition and separated by the wall, wherein the impingement hole communicates with the upstream end and the effusion hole communicates with the downstream end.