Abstract:

In order to assess the effect of the classical fluid-to-fluid modeling technique of critical heat flux (CHF) applied to horizontal helically coiled tubes, CHF experiments for HFC-134a flow boiling in horizontal helically coiled tubes heated with high power DC source were carried out. The results of applying Ahmad and Katto model indicated that the flow scaling factor determined with the two models produced bigger errors for CHF modeling in horizontal helically coiled tubes, and both Ahmad and Katto model overestimated the experimental data. Based on the data analysis, an empirical correlation for flow scaling factor was proposed. The calculation results showed that this correlation predicted the CHF in horizontal helically coiled tubes under the experimental conditions within an error band of ±20％, and was obviously superior to Ahmad and Katto model in precision.

Key words: helically coiled tubes, flow boiling, critical heat flux, fluid-to-fluid modeling, HFC-134a