Patent ID: 7849915

Claim:
A single heat exchange tube having a flat shape comprising: a plurality of fluid paths having a circular cross section extending in a longitudinal direction of the tube, the plurality of fluid paths being parallel with each other; wherein the tube has a distance between two adjacent fluid paths in the heat exchange tube defined as Wt, and a circumferential thickness between an outer surface of the heat exchange tube and an inner surface of an outermost fluid path is defined as Ht, wherein the distance Wt and the circumferential thickness Ht have a relationship as: 0.63 ≦Ht/Wt≦ 0.77; wherein the tube is used for a high-pressure side heat exchanger in a vapor-compression refrigerant cycle with CO 2 refrigerant, wherein each of the fluid paths has a diameter defined as Dp, wherein the tube is made of material having a tensile strength defined as S, and wherein the relationship among the distance Wt, the tensile strength S and the diameter Dp is defined as: (0.73−0.0036 ×S )× Dp≦Wt ≦(1.69−0.0084 ×S )× Dp.