Natural Convection From Horizontal Cylinders at Near-Critical Pressures-Part II: Numerical Simulations

作者：Warrier Gopinath R^*; Rousselet Yohann; Dhir Vijay K

来源：Journal of Heat Transfer-Transactions of the ASME, 2013, 135(2).

DOI：10.1115/1.4007673

• natural convection
• near-critical and supercritical pressures
• horizontal cylinder
• numerical simulation

A numerical investigation of laminar natural convection heat transfer from small horizontal cylinders at near-critical pressures has been carried out. Carbon dioxide is the test fluid. The parameters varied are: pressure (P), (ii) bulk fluid temperature (T-b), (iii) wall temperature (T-w), and (iv) wire diameter (D). The results of the numerical simulations agree reasonably well with available experimental data. The results obtained are as follows: (i) At both subcritical and supercritical pressures, h is strongly dependent on T-b and T-w. (ii) For T-w< T-sat (for P< P-c) and T-w< T-pc (for P> P-c), the behavior of h as a function of Tw is similar; h increases with increase in Tw. (iii) For P> P-c and large T-w (T-w> T-pc), natural convection heat transfer occurring on the cylinder is similar that observed during film boiling on a cylinder. The heat transfer coefficient decreases as T-w increases. (iv) For subcritical pressures, the dependence of h on D (sic) D-0.5 in the range 25.4 <= D <= 100 mu m. For larger values of D (500- 5000 mu m), h (sic) D-0.24. (v) For supercritical pressures, the dependence of h on D is h (sic) D-0.47 in the range 25.4 <= D <= 100 mu m. For larger values of D (500- 5000 mu m), h proportional to D-0.27. (vi) For a given P, the maximum heat transfer coefficient is obtained for conditions where T-b< T-pc and T-w >= T-pc. Analysis of the temperature and flow field shows that this peak in h occurs when k, C-p, and P-r in the fluid peak close to the heated surface. [DOI: 10.1115/ 1.4007673]

• 出版日期2013-2