Effects of hot gas passages on the performance of multi-pass cast-iron sectional boilers

Thermal performance of a simplified cast-iron sectional boiler is numerically investigated in the present study. Computations are performed using the water mass flow rates in the range of 0.2 kg/s ≤ ṁ ≤ 0.5 kg/s. Eight different scenarios, including the circle, square, horizontal ellipse (HE) and vertical ellipse (VE) with aspect ratios (Ar) of 1.2, 1.4, and 1.6 have been considered for the cross section of the hot gas passage. Flow patterns and thermal performance of all multi-pass cases are studied and compared with those of the single-pass sectional boiler. Several results have been obtained in this study. For example, depending on the hot gas passage shape, different vortical structures are realized within the section in which the section with square passage showed more complex flow behavior in comparison to the other cases. On the other hand, it is revealed that among the under consideration cases, the section with a square passage has the highest heat transfer, pressure drop, and thermal performance. Beyond the case with a square passage, section equipped with a vertical elliptic (Ar = 1.6) passage is identified as the highest thermal performance. It was hoped the obtained results from this research arouse interest among the thermal engineers.