Kong's apex sweep: the apex trend is not a settled reference, and the model sits between two of them
Tier 3: CFD, co-simulation or another model.
- What was compared
- The thermal improvement index (Kong et al., 2018, Eq. 12), the heat transfer rate of a ring relative to the 60° ring, for five vertical delta rings of the same heat transfer surface area on the same tower with the cooling-delta apex angle opened from 60° to 180°, windless and at 6 and 12 m/s.
- Against
- Two CFD studies by one group: Kong et al. (2018, IJHMT 116, Table 1 and Fig. 7), digitised, and its sister paper (Kong et al., 2018, IJHMT 118, Table 3). Both are models and not measurements.
- The agreement
- The two references disagree by a factor of 2.3, +10.39% and +24.37% from 60° to 180°, and the model lies between them at +12.81% to +16.21%. Against the first paper's windless indices the model is 23 to 47% high from 90° to 180°; the shape agrees more closely, with 65.8% of the improvement in the first 30° step against 55.2%.
- What it shows
- The case brackets the model between two published CFD studies that no single correction can match together, and shows that the shape of the index's rise with the apex angle agrees better than its magnitude. Kotzé's downstream loss and the tower inlet loss state no accuracy, so the case carries no model-form uncertainty.
- Source
- Y. Kong, W. Wang, L. Yang, X. Du, Y. Yang, 'Thermo-flow performances of natural draft direct dry cooling system at ambient winds', International Journal of Heat and Mass Transfer 116 (2018) 173-184; read against its sister paper, Y. Kong, W. Wang, X. Huang, L. Yang, X. Du, 'Annularly arranged air-cooled condenser to improve cooling efficiency of natural draft direct dry cooling system', IJHMT 118 (2018) 587-601Table 1 (geometry and design condition), Eqs. (7)-(9) (the radiator model), Eq. (12) and Fig. 7 (the thermal improvement index at zero wind)