The heat exchanger is widely applied to many thermal systems, and its structure significantly affects the flow and heat transfer characteristics. 3-D finned tube is a new type of carbon steel heat exchanger element that is low-fin-tube geometry with integral fins, which has larger heat transfer area and higher heat exchange efficiency. The current researches on the 3-D finned tube mainly focus on the flow and heat transfer performance of single tube by changing the structure parameters of fin or the condition of working medium. However, a reasonable tube bundle arrangement must be considered to obtain a compact structure in the engineering applications. So in the study, experiments are performed to investigate the air side flow and heat transfer characteristics of 3-D finned tube bundle with different geometries. The effects of varied transversal tube pitches, longitudinal tube pitches, and fin heights on Nu, Eu, and j/f are presented and discussed. The predictive correlations of 3-D finned tube bundle for Nu and Eu are proposed based on the presented data, and they can provide a theoretical reference for the industrial applications of 3-D finned tube. Finally, the flow and heat transfer characteristics of 3-D finned tube bundle are contrasted with those of other types of finned tube bundle from extant studies, and the results show that the 3-D finned tube bundle heat exchanger has higher air-side heat transfer performance and lower pressure drop. (C) 2018 Published by Elsevier Ltd.