Disclosed is a
heat exchanger, comprising a first plate, a first connecting portion, a second plate, a second connecting portion and a third plate, the second plate being located between the first plate and the third plate, the
heat exchanger comprising a first side and a second side, the first connecting portion being located on the first side of the
heat exchanger and the second connecting portion being located on the second side of the heat exchanger, the first connecting portion, the first plate and the second plate being integral, the second connecting portion, the second plate and the third plate being integral, a first flow passage being between the first plate and the second plate, The first plate and the second plate are arranged in a sealed manner, the sealed area between the first plate and the second plate surrounds at least the first flow passage, there is a second flow passage between the second plate and the third plate, the second plate and the third plate are arranged in a sealed manner, the sealed area between the second plate and the third plate surrounds at least the second flow passage, the heat exchanger is formed by folding the same plate, there is no need to stack them one by one, it is convenient to install.