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Experiments have been performed for evaporation of refrigerants R-134a, R-410A, and R-507A on the outside of a horizontal bundle composed of enhanced boiling Turbo-BII HP tubes. Hot water flowing through the tubes was used as the heat source. Water temperature measurements were made at numerous axial locations within the tubes to obtain the water's temperature profile and, thus, measure twelve local heat transfer coefficients in the bundle. Pool boiling tests to measure the corresponding nucleate boiling curves were also obtained. Tests were conducted with a 20-tube bundle over ranges of heat flux (8-64 kW/m 2 ), mass flux (4-38 kg/[m 2 s]), and vapor quality (8-78%). The bundle test results showed a significant contribution of convection from rising bubbles to the heat transfer process with local heat transfer coefficients as large as 1.6 times those of nucleate pool boiling in the case of R-134a. Refrigerants R-507A and R-410A also showed bundle enhancement effects but less so than R-134a.

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