At Nucleate Boiling Heat Transfer Zeotropicmixtures a Horizontal Tubes

Despite numerous empirical relationships, currently there is no sufficiently reliable and physically reasonable methodology for calculating the heat transfer coefficient at boiling the zeotropic binary blends. The main reason is the complexity of the boiling process mechanism. Zeotropic blends have the non-isothermal phase transition or the temperature glide. To perform the analysis, the results of experimental work on boiling the zeotropic blends inside the horizontal smooth tubes were processed. The studies were carried out with the horizontal smooth steel and copper tubes; the mass velocities were varied within 50–583 kg/m²*s; the specific heat flux was varied from 1 to 45 kW/m² . The experimental data, corresponding to the region of nucleate boiling, were compared with the calculated dependencies. The dependences corresponding to pool boiling were also analyzed. It was proposed to determine the heat transfer coefficient by Gogonin’s dependence (2006); this coincides well with the experimental data. This dependence takes into account the effect of wall thermal properties and its roughness on heat transfer. Moreover, it was found out that, in contrast to pool boiling, for the forced vapor-liquid flow in pipes at nucleate boiling, the diffusion processes are not important.

Keywords:
heat transfer at boiling, zeotropic blends, diffusion processes. 
УДК 536.423.4.535.5

At Nucleate Boiling Heat Transfer Zeotropicmixtures a Horizontal Tubes