Heat transfer performance outside of a horizontal 3-D externally rectangular finned tube and tube bundle was experimentally investigated with R22 condensing outside. Condensing coefficient of a horizontal finned tube was obtained through a Method of Thermal Resistance Separation. The outside condensation coefficient of two longitudinal fin pitches (1.2mm and 0.8mm) of the horizontal rectangular finned tubes (d_o = 12mm) was in comparison with each other and with that of a horizontal 3-D grooved tube (d_o = 19mm) with different fin height. And the overall heat transfer coefficient was compared under different water Reynolds number inside the three horizontal tubes. The 3-D externally rectangular finned tube with longitudinal fin pitch of 1.2mm was introduced into a shell-and-tube heat exchanger for the first time. The condensation capacity and the tube's side pressure drop of the heat exchanger were compared with that of another shell-and-tube condenser (WN40D) with 3-D grooved tube bundle (d_o = 16mm). The experimental results showed that the outside condensation coefficient of the 3-D rectangular finned tube with 1.2mm fin pitch was about 50% ～ 100% higher than that of finned tube with 0.8mm fin pitch, and that of the latter was a little higher than that of the 3-D grooved tube. Among the three tubes, the overall heat transfer performance of the rectangular finned tube with 1.2mm fin pitch was the best. And the condensation capacity of the heat exchanger with 1.2mm fin pith rectangular finned tube bundle was equivalent to that of WN40D condenser.
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