Improvement of heat transfer with perforated circular holes in finned tubes of air-cooled heat exchanger

The present study investigated the effect of perforated circular finned-tube (PCFT) on the convective heat transfer performance of circular finned-tube heat exchangers. The air-side convective heat transfer coefficients increased by 3.55% and 3.31% for 2-hole and 4-hole PCFT cases, respectively. The increase in the convective heat transfer coefficient was related to the reduction of the recirculation region by introducing the perforations at the flow-separation locations on the finned tube. The pressure drop across the finned-tube bundles increased by 0.68% and 2.08% for the 2-hole PCFT and 4-hole PCFT cases, respectively. The greater pressure drop in the case of the 4-hole PCFT might be due to excessive flow disturbances produced by multiple perforations. The fin factor defined as the ratio of the % increase of the convective heat transfer coefficient and that of the pressure drop was 5.19 for the 2-hole PCFT case, whereas that was 1.59 for the 4-hole PCFT case.