Abstract
Abstract In order to investigate heat transfer characteristics of steam/nitrogen condensation inside horizontal enhanced condensation channels (HECCs), experiments have been performed, respectively, inside HECC and horizontal circular channel (HCC). HECC is formed by inserting different reinforcers into HCC including horizontal multi-start straight channels (HMSSCs) and horizontal spiral channels (HSCs). Effects of nitrogen mass fractions on average condensation heat transfer coefficients (CHTCs), average outlet condensate mass flowrates (CMFRs), and average steam-side pressure drops (SSPDs) are analyzed, respectively. The results indicate that HECC has better condensation performance than HCC under the same conditions, while average SSPDs of HECC will increase slightly. Then, HMSSC is compared against HCC, and enhancement factors of average CHTCs and average outlet CMFRs are about 1.45 and 1.12, respectively, while the enlargement factor of average SSPDs is about 1.16. Similarly, HSC is compared against HCC, and enhancement factors of average CHTCs and average outlet CMFRs are about 1.25 and 1.05, respectively, while the enlargement factor of average SSPDs is about 1.12.
Highlights
Heat transfer performance widely exists in the natural environment and industrial production, and the heat transfer enhancement research is carrying on continuously [1,2]
The results show that the total condensation heat transfer coefficients (CHTCs) would decrease 26.4% with 8% NC gas mass fraction
The results show that the calculative Nucal are consistent with the experimental Nuexp for steam/nitrogen condensation inside the horizontal circular channel (HCC), and all of the data points are within the range of ±15% error, with the correlation coefficient of 0.903 and a standard error of 0.175, respectively
Summary
Heat transfer performance widely exists in the natural environment and industrial production, and the heat transfer enhancement research is carrying on continuously [1,2]. Steam condensation involves a complex phase-change heat transfer process and is affected by many factors, especially when the steam condensation is carried out inside the horizontal restricted channels with a small amount of noncondensable (NC) gas. It is extremely necessary for us to continuously study the steam condensation mechanism and heat transfer characteristics with NC gas inside the horizontal restricted channels. In steam and NC gas condensation processes, the NC gas diffusion layer (its thermal resistance is much higher than that of the condensate liquid film) comes to be the main resistance of steam/NC gas condensation. When the steam/nitrogen velocity is low, the asymmetrical gas–liquid two-phase distribution caused by the density difference could affect the heat transfer [6], and the condensation heat transfer coefficients (CHTCs) at the top and bottom of the tube will be quite different
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