Experimental Study on the Flow Boiling Heat Transfer in Horizontal Tubes With Composite Structure

Abstract

Abstract To fill the research gap in the study of R410A flow boiling on composite surfaces, four heat exchange tubes with different structures were tested: an enhanced tube with herringbone teeth (EHT_HB), a tube with a dimple structure (EHT_DIM), a tube with a composite herringbone tooth/dimple (EHT_HB/DIM), and a smooth tube for comparison with a baseline. The experimental conditions were set as follows: saturation temperature 279K, mass flux range of 50–205 kg/(m2.s), and vapor quality 0.2–0.8. After confirming the validity of the experimental results, the effect of the mass flux on the flow boiling heat transfer and pressure drop characteristics were examined. Results showed that the flow boiling heat transfer coefficient and pressure drop increased with the increase of the mass flux and the vapor quality in the tested tubes. The EHT_HB/DIM tube was found to combine the advantages of the two structures to have the highest heat transfer coefficient. The average value was found to be 43.75% higher than that of the smooth tube. Meanwhile, the average flow boiling heat transfer coefficients of the EHT_HB tube and the EHT_DIM tube were found to be 1.15 and 1.35 times that of the smooth tube, respectively. From the perspective of frictional pressure drop, it was concluded that the EHT_HB/DIM tube exhibited the maximum frictional pressure drop. The optimum working conditions of the enhanced tubes were determined by introducing a performance factor that captures the combined effects of the heat transfer and pressure drop.