The current study presents the experimental results for the boiling heat transfer coefficient of R134a flowing inside a 5 mm inner diameter, smooth horizontal tube. The study cases are set for pressures ranging from 5 to 10 bar, and mass fluxes from 300 to 400 kg/m2s. The heat transfer coefficients are measured at vapor qualities from 0.01 to 1.3, particularly in small quality increments over the high quality region.

The experimental heat transfer coefficients are compared with the predicted results by the method of Wojtan et al. [1,2]. The method gives a good prediction in the quality range 0.1–0.7. There exist large errors in the high quality region, and the maximum value can reach −90%. The method is modified using the correlation by Del Col et al. [2] for dryout inception and a new proposed approach for the dry angle. The modified method improves the predicted results with good estimation in the quality range 0.1–0.8, and the maximum error in the high quality region is reduced to −60%.

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