Q3-4 Effects of Tube Pitch and Number of Rows in Air-Cooled Heat Exchanger Performance

Z. H. Yang

HTRI began its study of air-cooled heat exchangers in the early 1970s. In 1971, Report ESG-3 presented a state-of-the art literature review on the effect of finned tube geometry parameters. The following year, ESG-4 presented survey results and an evaluation of heat transfer and pressure drop correlations for ideal finned tube banks with staggered tube layouts.

In the 1980s, HTRI conducted an experimental and analytical study of air-cooled heat exchangers. Report AC-1 documented air-cooled heat exchanger performance under both natural and forced draft conditions using the HTRI air-cooled exchanger tube bank. Based on that study, HTRI established a semi-empirical method that predicted heat transfer data with a maximum of ± 30 percent. A parametric study of air-cooler finned tube bundles, presented in ESG-10, showed that HTRI’s heat transfer and pressure drop methods predicted most experimental data within ± 25 percent accuracy.

Research Brief 5-1 documented the results of row effects in a finned tube bundle of preheater tubes with zero fin-tip clearance using 1-, 2-, and 4-row tube banks. Row effects for both pressure drop and heat transfer were predicted too conservatively, even when the method was adjusted. In 1986, HTRI tested pitch and tube layout effect on heat transfer and pressure drop in high-finned tube banks and improved the method using data presented in ESG-12.

To further evaluate and improve our current method of heat transfer and pressure drop for air-cooled heat exchangers, HTRI conducted an experimental study to test

  • the effect of tube pitch with a variety of transverse pitches
  • the effect of tube row on pressure drop and heat transfer in air-cooled heat exchangers with staggered equilateral triangular arrangements