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 set-up 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 the tube bundle shows an increase in overall heat transfer coefficient (HTC) with an increase in heat flux. However, the 5x3 tube bundle resulted in a greater heat transfer rate as compared to the 2x3 tube bundle due to the bundle effect. Further, both the 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 5x3 tube bundle is not twice that of 2x3 tube bundle rather it is quite lesser which further deteriorates with an increase in P/D ratio. The data is predicted within 15% using correlation.

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