STANFORD GEOTHERMAL PROGRAM QUARTERLY REPORT OCTOBER 1 – DECEMBER 31, 1996

摘要

The objective of this work is to improve the understanding of the process of boiling in porous media. The ultimate goal is to obtain the two important but currently unknown functions of relative permeability and capillary pressure functions. One horizontal and one vertical experiment were conducted using Berea sandstone core samples. Difficulties were encountered in analyzing the results of the first preliminary boiling experiment: namely the apparent existence of a steam phase at inappropriately low temperatures. These results suggested several improvements to the design of the experimental apparatus. Upon the completion of these modifications, further horizontal and vertical experiments were conducted. Three-dimensional porosity and steam saturation distributions were determined using an X-ray CT scanner. The maximum difference between the centerline and wall temperatures for the horizontal experiment was found to be less than 2 oC, therefore, wall measurements were shown to be adequate to represent the temperature of a circular slice along the core. The steam saturation distributions calculated from the X-ray CT data did not show a significant steam override in any of the experiments. Steady-state steam saturation data showed a progressive boiling process with the formation of the three regions of steam, two-phase and liquid as the heat flux was increased. The previous problem of steam existing at inappropriate temperatures was not observed in the later vertical experiment. A comparison of the three-dimensional saturation profiles from both experiments showed a longer two-phase zone in the horizontal boiling case than that in the vertical case.