M.Ing. / An experimental investigation was conducted into the heat transfer characteristics of horizontal smooth, micro-fin and herringbone tubes during in-tube condensation. The study focused on the heat transfer coefficients of refrigerants R-22, R-134a and R-407C inside the three tubes. The herringbone tube results were compared to the smooth and micro-fin tube results. The average increase in the heat transfer coefficient when compared to the smooth tube was found to be as high as 322% with maximum values reaching 336%. When compared to the micro-fin tube, the average increase in heat transfer coefficient was found to be as high as 196% with maximum values reaching 215%. A new unified correlation was also developed to predict the heat transfer coefficients in a herringbone and micro-fin tube. The correlation predicted the semi-local heat transfer coefficients accurately with 96% and 89% of the data points falling in the ± 20% region for the herringbone and micro-fin tube respectively. The average heat transfer coefficients were also accurately predicted with all the data points for the herringbone tube and 83% of the data points for the micro-fin tube falling in the ± 20% region. The trend of the new correlation also fitted the data accurately and the conclusion was made that the correlation is accurate and could be used successfully in practice.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:14738 |
| Date | 27 November 2008 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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