A heat exchanger having a first heat transfer tube with a first primary straight part and a first secondary straight part is provided. The heat exchanger includes a first primary bond part and a first secondary bond part. The first primary bond part is welded to the first secondary bond part to form a first primary bond that bonds the first primary straight part and the first secondary straight part of the first heat transfer tube. The first primary bond limits a first primary aperture and a first secondary aperture formed by the holes of the bond parts, wherein the straight parts of the first heat transfer tube extend through the first primary bond via the apertures.