A heat exchanger assembly for an environmental control system, comprising: an inlet header arranged to receive a first fluid that flows along a first axis; a primary heat exchanger arranged to receive a second fluid that flows along a second axis that is disposed transverse to the first axis, the primary heat exchanger arranged such that the first fluid flows through the primary heat exchanger along the first axis; and an outlet header operatively connected to the primary heat exchanger and arranged to exhaust the first fluid, the outlet header comprising: a first side panel having a first side panel first portion, a first side panel second portion, and a first side panel arcuate portion extending between the first side panel first portion and the first side panel second portion along the first axis, and a second side panel spaced apart from the first side panel, the second side panel having a second side panel first portion, a second side panel second portion, and a second side panel arcuate portion extending between the second side panel first portion and the second side panel second portion; wherein: the first side panel first portion, the first side panel second portion, and the first side panel arcuate portion extends from a first side panel first end towards a first side panel second end along the second axis; the second side panel first portion, the second side panel second portion, and the second side panel arcuate portion extends from a second side panel first end towards a second side panel second end along the second axis; the heat exchanger further comprises a front panel extending between a front panel first end and a front panel second end, wherein the front panel first end is connected to the first side panel first end and the front panel second end is connected to the second side panel first end; and wherein a first side panel extension extends from an end of the first side panel arcuate portion towards the first side panel second end. an inlet header arranged to receive a first fluid that flows along a first axis; a primary heat exchanger arranged to receive a second fluid that flows along a second axis that is disposed transverse to the first axis, the primary heat exchanger arranged such that the first fluid flows through the primary heat exchanger along the first axis; and an outlet header operatively connected to the primary heat exchanger and arranged to exhaust the first fluid, the outlet header comprising: a first side panel having a first side panel first portion, a first side panel second portion, and a first side panel arcuate portion extending between the first side panel first portion and the first side panel second portion along the first axis, and a second side panel spaced apart from the first side panel, the second side panel having a second side panel first portion, a second side panel second portion, and a second side panel arcuate portion extending between the second side panel first portion and the second side panel second portion; a first side panel having a first side panel first portion, a first side panel second portion, and a first side panel arcuate portion extending between the first side panel first portion and the first side panel second portion along the first axis, and a second side panel spaced apart from the first side panel, the second side panel having a second side panel first portion, a second side panel second portion, and a second side panel arcuate portion extending between the second side panel first portion and the second side panel second portion; wherein: the first side panel first portion, the first side panel second portion, and the first side panel arcuate portion extends from a first side panel first end towards a first side panel second end along the second axis; the second side panel first portion, the second side panel second portion, and the second side panel arcuate portion extends from a second side panel first end towards a second side panel second end along the second axis; the heat exchanger further comprises a front panel extending between a front panel first end and a front panel second end, wherein the front panel first end is connected to the first side panel first end and the front panel second end is connected to the second side panel first end; and wherein a first side panel extension extends from an end of the first side panel arcuate portion towards the first side panel second end. the first side panel first portion, the first side panel second portion, and the first side panel arcuate portion extends from a first side panel first end towards a first side panel second end along the second axis; the second side panel first portion, the second side panel second portion, and the second side panel arcuate portion extends from a second side panel first end towards a second side panel second end along the second axis; the heat exchanger further comprises a front panel extending between a front panel first end and a front panel second end, wherein the front panel first end is connected to the first side panel first end and the front panel second end is connected to the second side panel first end; and