(EN)
Disclosed is a heat exchanger tube having a flattened pipe having two non-flattened ends connected with a first opening and a second opening. A plurality of first half-slacking narrows and a plurality of second half-slacking narrows are arranged in an interlaced zigzag pattern such that a winding flow channel is formed inside the flattened pipe to increase heat exchange efficiency. In a preferred embodiment, each of the first half-slacking narrow and the second half-slacking narrow consists of a pair of adjacent indentations formed on the two opposing flattened surfaces of the flattened pipe respectively to achieve a unit body structure of the flattened pipe.