Effect of Tube Rows on Two-Phase Heat Transfer Characteristics of Water Over Staggered Tube Bundles Under Flow Boiling Mode

Tube bundles are an integral part of the two-phase heat exchangers and are employed in numerous commercial applications. Present research compares two kinds of horizontal staggered tube bundles under upward crossflow boiling to see how tube rows affect the heat transfer coefficient (HTC). The experimental setup developed houses the tube bundle for temperature measurements and facilities the recording of high-speed images at different operating conditions. The investigation is carried out for heat fluxes of 10–75 kW/m2, mass fluxes of 20–100 kg/m2s, and P/D ratios of 1.25, 1.6, and 1.95, with distilled water as the working fluid. It is observed that both tube bundles show an increase in overall HTC with an increase in heat flux. However, the 5 × 3 tube bundle resulted in a greater heat transfer rate as compared to the 2 × 3 tube bundle due to the bundle effect. Further, both tube bundles have a diminishing trend of HTC with a rise in mass flux. The rate of rising in HTC was found to decrease with an increase in the number of tube rows in the tube bundle and with an increase in the P/D ratio. Therefore, interestingly it is observed that the increase in bundle average HTC of 5 × 3 tube bundle is not twice that of 2 × 3 tube bundle rather it is quite lesser which further deteriorates with an increase in P/D ratio. The row-wise and bundle average HTC obtained is also predicted with a dimensionless correlation within an error of ± 15%.