Kröger Example 8.4.1

Plume recirculation on a forced-draft bank

Tier T: a textbook worked example - a published answer, not a measurement.

What was compared: The recirculation effectiveness and the inlet flow ratio of a forced-draft bank of six bays in still air, in which hot plume air is drawn back under the fan platform to the inlet.
Against: Kröger's worked Example 8.4.1 (Kröger, Vol. 2, Section 8.4), which evaluates the recirculation correlation of Duvenhage and Kröger (Eq. 8.4.25), and the inlet flow ratio of his Example 8.3.1. Both are published calculations and not measurements.
The agreement: The recirculation effectiveness of 0.9924 is reproduced to within 0.004%, and the inlet flow ratio of 0.985 lies within the case's tolerance of ±0.5%. Applied to Kröger's flow-proportional heat transfer rate of the bank, the model's effectiveness gives 73.153 MW against his printed 73.179 MW, a difference of 0.036%.
What it shows: The agreement verifies that the model implements the still-air recirculation correlation of Duvenhage and Kröger as Kröger applies it to a bank. The correlation states no accuracy, so the case says nothing about how well recirculation on a built bank is predicted.
Source: Kröger, D.G., Air-Cooled Heat Exchangers and Cooling Towers: Thermal-Flow Performance Evaluation and Design (PennWell, 2004)Vol. 2, Example 8.4.1 (extending Examples 8.1.1 and 8.3.1), §8.4 Eqs. 8.4.10-8.4.25