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    FLOW BOILING BEHAVIORS OF VARIOUS REFRIGERANTS INSIDE HORIZONTAL TUBES: A COMPARATIVE RESEARCH STUDY
    (Eskisehir Technical University, 2022) Turgut, Oğuz Emrah; Asker, Mustafa
    In this study, convective boiling behaviors of refrigerants (R22, R134a, R290, R404a, R410a, R600, R507, R717, and R744) are compared with existing flow boiling correlations. Flow boiling heat transfer rates under the primary influences of vapor quality and mass flux are plotted and compared with the experimental results that are extracted from the literature. A statistical approach is introduced for error analysis and a valid correlation is proposed for each refrigerant. Correlation of Wojtan et al. with 30% of experimental data in 20% error region is selected as the best correlation while Shah Correlation with 10% of experimental data in 20% error regions performs the worst. The result of the analysis indicates that flow boiling heat transfer values are strongly dependent upon mass velocity and heat flux. It is observed that existing correlations are in good agreement with experimental works at low heat flux rates whereas deviations are getting bigger for high heat flux rates.
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    Öğe
    Novel saturated flow boiling correlations for R600a and R717 refrigerants
    (Taylor & Francis Inc, 2021) Turgut, Oğuz Emrah; Genceli, Hadi; Asker, Mustafa; Çoban, Mustafa Turhan
    This research study provides a detailed analysis of the two-phase flow boiling heat transfer coefficients of R600a and R717. In addition, it proposes novel saturated flow boiling heat transfer correlations for these two refrigerants. In this context, 1306 experimental data points for R600a and 885 data samples for R717 are extracted from the literature works to develop new flow boiling models. Two different correlations are constructed under different forms of baseline frameworks for each refrigerant. The proposed flow boiling model for R600a utilizes the dimensionless numbers and operational parameters of the best performing literature correlations for this refrigerant while the model developed for R717 takes the advantage of piecewise continuous correlation form which successfully trace the tendencies of heat transfer coefficient with varying vapor qualities. It is found that the new model for R600a has a mean absolute error of 12.4% and mean relative error of 0.1, predicting 78.5% of the entire database within +/- 20.0% error band whereas the proposed correlation for R717 has an absolute error value of 17.3% having 65.3% of the data within +/- 20.0% error band, which are much better and accurate estimations compared to those obtained by the existing flow boiling models for R717 refrigerant.