Experimental Study of Boiling Heat Transfer From a Sphere Embedded in a Liquid-Saturated Porous Medium

Abstract

Boiling heat transfer from a sphere embedded in a porous medium composed of nonheated glass particles was studied under steady-state and transient quenching conditions. In the experiments, the diameter of the nonheated glass particles forming the porous layers was varied parametrically. Freon-113 was used as the test liquid. Experimental results showed that the maximum heat flux increased monotonically with increasing glass particle diameter and approached an asymptotic value corresponding to the maximum heat flux obtained in a pool free of glass particles. It was also observed that the minimum heat flux was nearly insensitive to the particle size and the film boiling heat transfer coefficient increased slightly with decreasing particle size. In the nucleate boiling region, the heat transfer coefficient showed a much weaker dependence on wall superheat in the presence of particles. Transient data indicated that the surface temperature was not uniform during quenching. Therefore, different maximum heat fluxes were obtained depending on the location of the thermocouple whose temperature history was employed in recovering the transient boiling curve. However, for some applications, cooling rates predicted by imposing the steady-state boiling curve may not be in large error.

Principles of Heat Transfer in Porous Media

“…For example, the experimental results of Fand et al (1987) for heating of a 2-mm-diameter tube in a paeked bed of glass spheres-water (d = 3 mm, Bo = 0.003) shows that unlike the results of Fukusako et al no monotonie inerease in q is found for (To -T.) > 100 oe. Tsung et al (1985) use a heated sphere in a bed of spheres (d 2: 2.9 mm).…”

Measurement of Critical Heat Flux in a Candu End Shield Consisting of a Vertical Surface Abutting a Packed Bed of Steel Shielding Balls

“…Some experimental studies of boiling on surfaces abutting porous media are available, but none directly reflect the geometry of interest. These include studies of heated cylinders in liquid-saturated sands with particle diameters ranging from 0.16 to 1.5 mm [32], horizontal heating surfaces underneath a packed bed of particles with diameters ranging from 1 to 16 mm [33], and spherical heating surfaces in a packed bed of particles with diameters ranging from 2.9 to 19 mm [34]. These investigations agreed in observing a positive relationship between particle size and CHF.…”

Coolability of a Corium Pool in a Debris Bed -- Impact of Debris Size, Steam and Liquid Flowrate, Tilting Angle and Pressure on Critical Heat Flux (CHF)

“…Fukusako and al. [11], Spencer [12] and Tung and Dhir [13] studied different boiling regimes for different surface materials, shapes and orientations, and different ball materials and sizes. Fukusako and Tung and Dhir showed that CHF increases with ball diameter.…”