An unfinned heat exchanger , comprising: a heat exchange tube which comprises a body, a fluid passage formed in said body , and a manifold connected to said heat exchange tube , wherein said heat exchange tube comprises a first row of heat exchange tube and an adjacent second row of heat exchange tube , at least one heat exchange tube of said first row of heat exchange tube has a strip shape and is twisted into a spiral shape, at least one heat exchange tube of said second row of heat exchange tube has a strip shape and is twisted into a spiral shape, wherein two opposite edges of the strip-shaped heat exchange tube of said first row of heat exchange tube have a wave shape and have a first wave peak , a first wave trough and a first intersection point in a projection on a plane defined by an arrangement direction (DA) of the first row of heat exchange tube and a longitudinal direction of the heat exchange tube of the first row of heat exchange tube , two opposite edges of the strip-shaped heat exchange tube of said second row of heat exchange tube have a wave shape and have a second wave peak , a second wave trough and a second intersection point in a projection on a plane defined by an arrangement direction (DA) of the second row of heat exchange tube and a longitudinal direction of the heat exchange tube of the second row of heat exchange tube , and characterised in that said first wave peak and first wave trough are staggered from said second wave peak and second wave trough in a longitudinal direction of the heat exchange tube of the first row of heat exchange tube or second row of heat exchange tube . a heat exchange tube which comprises a body, a fluid passage formed in said body , and a manifold connected to said heat exchange tube , wherein said heat exchange tube comprises a first row of heat exchange tube and an adjacent second row of heat exchange tube , at least one heat exchange tube of said first row of heat exchange tube has a strip shape and is twisted into a spiral shape, at least one heat exchange tube of said second row of heat exchange tube has a strip shape and is twisted into a spiral shape, wherein two opposite edges of the strip-shaped heat exchange tube of said first row of heat exchange tube have a wave shape and have a first wave peak , a first wave trough and a first intersection point in a projection on a plane defined by an arrangement direction (DA) of the first row of heat exchange tube and a longitudinal direction of the heat exchange tube of the first row of heat exchange tube , two opposite edges of the strip-shaped heat exchange tube of said second row of heat exchange tube have a wave shape and have a second wave peak , a second wave trough and a second intersection point in a projection on a plane defined by an arrangement direction (DA) of the second row of heat exchange tube and a longitudinal direction of the heat exchange tube of the second row of heat exchange tube , and characterised in that said first wave peak and first wave trough are staggered from said second wave peak and second wave trough in a longitudinal direction of the heat exchange tube of the first row of heat exchange tube or second row of heat exchange tube . <EOS>