Pressure drop and heat transfer characteristics of refrigerant-114 boiling in a horizontal tube

The two-phase pressure drop and heat transfer characteristics of R-114 flowing in a horizontal tube were studied. Flow regime studies were also performed as a part of this effort. Boiling temperature was varied from 100 to 2500F and mass flux was varied from 0.12 to 3.4 x 106 lbm/hr-sq ft. No single method for predicting flow regime was found to be accurate over the range of conditions studied. The method proposed by Knowles was the best available for determining the stratified and intermittent flow regimes, and the analysis of Quandt was the most reliable in predicting the annular flow regime. Four correlations gave promising results when compared to the experimental, frictional pressure drop data. The Martinelli-Nelson correlation agreed fairly well with all of the data obtained. The degree of data scatter was, however, fairly large. Two correlations proposed by Chisolm which include a mass flux effect gave slightly better results when compared with the experimental data. The correlation proposed by Baroczy, generally, gave good results when applied to the medium-to-high mass flux data. The experimental heat transfer coefficient data could not be predicted accurately by a single correlation. The original Chen correlation offered the best agreement of any correlation considered. The degree of agreement between experimental data and correlation was improved by applying the original Chen correlation to the low mass flux data and Jallouk's modification to the remaining data