What extrapolating Robinson & Briggs costs, measured
Tier 2: measurement on a controlled rig.
- What was compared
- The air-side friction of Wu et al.'s three-row annular finned tube bundle as given by Robinson and Briggs' loss relation (Kröger, Eq. 5.5.6), at seven Reynolds numbers from 1176 to 4813. The bundle lies outside the relation's declared domain on its row count and fin height.
- Against
- Wu et al.'s fit to their own rig measurements of the bundle's friction factor (Wu et al., 2024, Table 1 and Eq. 49), with a stated deviation of 3.95% over that range. It is a measurement on a rig, and the case is Tier 2.
- The agreement
- The relation reads 22.0% low at Re 4813 and 42.3% low at Re 1176, worsening monotonically as the Reynolds number falls. The case's tolerance of 50% holds that magnitude.
- What it shows
- The deviation measures the cost of applying Robinson and Briggs' relation outside its fitted domain, and it provides an accuracy for no relation. Its sign, a loss read low and so an air flow read high, matches the residual of the cases on the Gatton tower.
- Source
- Y. Wu, Y. Liu, Z. Zhang, Q. Xiang, Y. Sun, X. Yang, S. Jiang, 'A quick measurement method of heat transfer coefficient and friction factor for finned tube bundle of the air cooler under large temperature difference', International Journal of Heat and Mass Transfer 227 (2024) 125556Table 1 (bundle I), Eq. (44) for the friction/acceleration split, Eq. (49) with its stated 3.95% and Re 1176-4813, and the sentence stating each compared correlation's applicability. Figs. 18-23 are the paper's own plots and are not digitised.