The flow boiling heat transfer characteristics of liquid nitrogen in three U-tubes with different curvature ratios were investigated experimentally. The effects of inlet pressure, heat flux, and curvature ratio on heat transfer characteristic are analyzed. The results indicate that the local heat transfer characteristics change obviously as fluid flows through the return bend, especially in the case of high heat flux. The drying out occurs near the inner wall of the return bend under high heat flux. A parameter Rh (down/up), which is defined as the ratio of heat transfer coefficient between the downstream and upstream section of U-bend, is proposed to evaluate the contributions of the curvature ratio to the heat transfer. It is found that the Rh (down/up) increases with the decrease of the curvature ratios. Furthermore, the experiments results of the average heat transfer coefficient are compared with the calculated results of the empirical correlations.
Flow Boiling Heat Transfer of Liquid Nitrogen in Heated U-Tubes
Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received October 15, 2012; final manuscript received September 20, 2013; published online November 7, 2013. Assoc. Editor: Wei Tong.
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Deng, D., Xie, S. W., Li, X. D., and Wang, R. S. (November 7, 2013). "Flow Boiling Heat Transfer of Liquid Nitrogen in Heated U-Tubes." ASME. J. Heat Transfer. February 2014; 136(2): 024501. https://doi.org/10.1115/1.4025542
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