A heat exchanger header (110;31OA-C) comprising: a first stage (112; 312) with a first unit, the first unit including: a first branched region (116; 316); a first common axis passing through a center of the first branched region; and first fluid channels (120; 320) extending from the first branched region, each of the first fluid channels including: a first end (122; 322) forming a portion of the first branched region; and a second end (124; 324) opposite the first end; wherein each of the first fluid channels defines a first spiral path with respect to the first common axis such that the first fluid channels are wound into a first spiral about the first common axis; and a second stage (112; 312) with second units, each of the second units including: a second branched region (126; 326); a second common axis passing through a center of the second branched region; and second fluid channels (130; 330) extending from the second branched region, each of the second fluid channels including: a first end (132; 332) forming a portion of the second branched region; and a second end (134; 334) opposite the first end; wherein each of the second fluid channels defines a second spiral path with respect to the second common axis such that the second fluid channels of corresponding second units are wound into respective second spirals about corresponding second common axes; wherein each of the second ends of the first fluid channels is connected to one of the second branched regions, such that each of the second branched regions is connected to one of the second ends of the first fluid channels. a first stage (112; 312) with a first unit, the first unit including: a first branched region (116; 316); a first common axis passing through a center of the first branched region; and first fluid channels (120; 320) extending from the first branched region, each of the first fluid channels including: a first end (122; 322) forming a portion of the first branched region; and a second end (124; 324) opposite the first end; wherein each of the first fluid channels defines a first spiral path with respect to the first common axis such that the first fluid channels are wound into a first spiral about the first common axis; and a first branched region (116; 316); a first common axis passing through a center of the first branched region; and first fluid channels (120; 320) extending from the first branched region, each of the first fluid channels including: a first end (122; 322) forming a portion of the first branched region; and a second end (124; 324) opposite the first end; wherein each of the first fluid channels defines a first spiral path with respect to the first common axis such that the first fluid channels are wound into a first spiral about the first common axis; and a first end (122; 322) forming a portion of the first branched region; and a second end (124; 324) opposite the first end; wherein each of the first fluid channels defines a first spiral path with respect to the first common axis such that the first fluid channels are wound into a first spiral about the first common axis; and a second stage (112; 312) with second units, each of the second units including: a second branched region (126; 326); a second common axis passing through a center of the second branched region; and second fluid channels (130; 330) extending from the second branched region, each of the second fluid channels including: a first end (132; 332) forming a portion of the second branched region; and a second end (134; 334) opposite the first end; wherein each of the second fluid channels defines a second spiral path with respect to the second common axis such that the second fluid channels of corresponding second units are wound into respective second spirals about corresponding second common axes; a second branched region (126; 326); a second common axis passing through a center of the second branched region; and second fluid channels (130; 330) extending from the second branched region, each of the second fluid channels including: a first end (132; 332) forming a portion of the second branched region; and a second end (134; 334) opposite the first end; wherein each of the second fluid channels defines a second spiral path with respect to the second common axis such that the second fluid channels of corresponding second units are wound into respective second spirals about corresponding second common axes; a first end (132; 332) forming a portion of the second branched region; and a second end (134; 334) opposite the first end; wherein each of the second fluid channels defines a second spiral path with respect to the second common axis such that the second fluid channels of corresponding second units are wound into respective second spirals about corresponding second common axes; wherein each of the second ends of the first fluid channels is connected to one of the second branched regions, such that each of the second branched regions is connected to one of the second ends of the first fluid channels.