Ernest Gyan Bediako, Petra Dancova, Tomas Vit

Abstract: This study presents an experimental investigation of heat transfer characteristics at low heat flux conditions. The focus is to compare experimental findings with qualitative descriptions of heat transfer coefficient reported in literature. The study also compares the experimental results with 3 correlations developed based on different theories. For the experimental conditions, R134a was the refrigerant used, heat fluxes ranged from 4.6-8.5 kW/m2 and mass flux from 200-300 kg/m2s. The experimental heat transfer coefficient results were also compared with Wojtan et al flow patterns map to determine the flow patterns observed during the study. In covering heat transfer coefficient over a broad range of vapor qualities, the findings revealed that, the qualitative descriptions proposed by different authors do not entirely validate the actual representation of heat transfer coefficient within the experimental conditions considered. At vapor qualities around zero (0), heat transfer coefficient rises to a maximum peak and decreases to a local minimum before increasing as vapor quality increases until it reaches dry-out. The flow pattern predicted are slug flow at low vapor-quality region, intermittent flow at mid vapor quality region and annular, dry-out and mist flow at high vapor quality region.

Keywords: heat transfer coefficient, mass flux, heat flux, vapor quality, flow pattern.

Date Published: October 23, 2022
DOI: 10.11159/jffhmt.2022.018

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