New empirical correlations for the condensation heat transfer coefficient of R134a/POE68 mixtures

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Robert S.

Journal of Thermal Analysis and Calorimetry, vol.0, no.0, 2025 (SCI-Expanded, Scopus)

• Publication Type: Article / Article
• Volume: 0 Issue: 0
• Publication Date: 2025
• Doi Number: 10.1007/s10973-025-14923-0
• Journal Name: Journal of Thermal Analysis and Calorimetry
• Journal Indexes: Scopus, Aerospace Database, Science Citation Index Expanded (SCI-EXPANDED), Academic Search Premier, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, Index Islamicus, INSPEC, Metadex, Civil Engineering Abstracts
• Open Archive Collection: Article
• Azerbaijan State University of Economics (UNEC) Affiliated: Yes

Abstract

This study investigates the effect of the R134a/POE68 mixture on the condensation heat transfer coefficient (HTC) in
horizontal smooth tubes with an outer diameter of 8 mm. Experiments were conducted at a condensation temperature of
40 °C, with mass fluxes ranging from 100 to 500 kgm−2 s−1 and oil concentrations between 0 and 10%. Results confirm that
the presence of oil reduces the HTC, with a more pronounced deterioration at higher oil concentrations. The enhancement
factor (EF) decreased from 0.95 to 0.76 at 5% oil and from 0.89 to 0.69 at 10% oil. Based on the experimental data, two
new correlations were developed for predicting the HTC of R134a/POE68 mixtures. The first correlation uses a two-phase
multiplier approach, yielding an average prediction error of 11.29%. The second correlation is based on mixture properties
and achieves an average prediction error of 9.38%. These correlations provide improved predictive accuracy and are suitable
for engineering applications involving refrigerant–oil mixtures.