An Inverse Stefan Problem Relevant to Boilover: Heat Balance Integral Solutions and Analysis

Stefan problems relevant to burning oil-water systems are formulated. Two moving boundary sub-problems are defined: burning liquid surface and formation of a distillation (“hot zone”) layer beneath it. The basic model considers a heat transfer equation with internal heat generation due to radiation flux absorbed in the fuel depth. Inverse Stefan problem corresponding to the first case solved by the heat balance integral method and dimensionless scaling of semi-analytical solutions are at issue

DETERMINATION OF THE AREA AFFECTED BY THE SPREAD OF BURNING FUEL DUE TO BOILOVER

Boilover is one of the most dangerous accidents that can happen in an atmospheric hydrocarbons storage tank, it happens when the water at the bottom of the storage tank is heated to a temperature where it is evaporate and push’s the hydrocarbons out of the tank causing a ground fire and flame enlargements. And the main objective of this study is determination of the area affected by the spread of ejected hydrocarbons from the storage tank due to boilover causing a ground fire which is extremely dangerous. And for achieving this objective a set of experiments have been performed on a hydrocarbons mixture consisting of 50 % Diesel oil and 50% Gasoline is used. This mixture has been chosen after running some experiments on three different types of mixtures. Tow set of experiments have been performed and from the result analysis we were able to find equation relating the volume of the mixture in the storage tank to the area affected. And from both set of experiments we found that the relation between the fuel volume and the area affected is best described as a polynomial relationship. Moreover a different set of experiments is also performed using crude oil which gave an unpromising result and we were unable to find an equation relating the area affected to the crude oil volume in the storage tank

Improving Methods of Frozen Wall State Prediction for Mine Shafts under Construction Using Distributed Temperature Measurements in Test Wells

Development of mineral deposits under complex geological and hydrogeological conditions is often associated with the need to utilize specific approaches to mine shaft construction. The most reliable and universally applicable method of shaft sinking is artificial rock freezing – creation of a frozen wall around the designed mine shaft. Protected by this artificial construction, further mining operations take place. Notably, mining operations are permitted only after a closed-loop frozen section of specified thickness is formed. Beside that, on-line monitoring over the state of frozen rock mass must be organized. The practice of mine construction under complex hydrogeological conditions by means of artificial freezing demonstrates that modern technologies of point-by-point and distributed temperature measurements in test wells do not detect actual frozen wall parameters. Neither do current theoretical models and calculation methods of rock mass thermal behavior under artificial freezing provide an adequate forecast of frozen wall characteristics, if the input data has poor accuracy. The study proposes a monitoring system, which combines test measurements and theoretical calculations of frozen wall parameters. This approach allows to compare experimentally obtained and theoretically calculated rock mass temperatures in test wells and to assess the difference. Basing on this temperature difference, parameters of the mathematical model get adjusted by stating an inverse Stefan problem, its regularization and subsequent numerical solution

Analysis of the structural integrity of a frozen wall during a mine shaft excavation using temperature monitoring data

This paper describes the results of the temperature monitoring of a frozen wall (FW) around the skip shaft of a potash mine under construction. The data on temperature measurements in control-thermal boreholes were used to parameterize the mathematical model of heat transfer, which allowed for the reconstruction of the temperature field throughout the entire cooled and frozen soil volume. The resulting temperature distribution in the FW zone for greater than 1 year was used to determine the distribution of the strength properties and calculate the temporary change in the limiting value of the external lateral load on an FW of a given thickness and specified thermomechanical properties. The obtained dependencies of the maximum external load on the FW can be used to optimize the operation mode of the freezing station at the ice holding stage (or passive freezing) to increase the energy efficiency of the system and ensure the structural integrity of the FW

DETERMINATION OF THE AREA AFFECTED BY THE SPREAD OF BURNING FUEL DUE TO BOILOVER

Boilover is one of the most dangerous accidents that can happen in an atmospheric hydrocarbons storage tank, it happens when the water at the bottom of the storage tank is heated to a temperature where it is evaporate and push’s the hydrocarbons out of the tank causing a ground fire and flame enlargements. And the main objective of this study is determination of the area affected by the spread of ejected hydrocarbons from the storage tank due to boilover causing a ground fire which is extremely dangerous. And for achieving this objective a set of experiments have been performed on a hydrocarbons mixture consisting of 50 % Diesel oil and 50% Gasoline is used. This mixture has been chosen after running some experiments on three different types of mixtures. Tow set of experiments have been performed and from the result analysis we were able to find equation relating the volume of the mixture in the storage tank to the area affected. And from both set of experiments we found that the relation between the fuel volume and the area affected is best described as a polynomial relationship. Moreover a different set of experiments is also performed using crude oil which gave an unpromising result and we were unable to find an equation relating the area affected to the crude oil volume in the storage tank

Numerical simulation of frozen wall formation in water-saturated rock mass by solving the Darcy-Stefan problem

Artificial ground freezing (AGF) is a common technology of shaft sinking through water-bearing strata. The AGF technique is used to create a frozen wall preventing shaft flooding. An additional factor that makes shaft sinking more complicated is associated with external groundwater flows occurred due to hydrostatic pressure gradients. In this paper, we study the influence of groundwater seepage on the frozen wall formation in fluid-saturated rock mass in the framework of the two-dimensional two-phase Darcy-Stefan problem. The results of numerical simulation of the thermal and hydraulic properties of the sandstone layer at the site of Petrikov Mining and Processing Plant are presented. It has been found that the external groundwater flow has a significant effect on the growth of a frozen wall in the case when the groundwater velocity magnitude is greater than or equal to 50 mm/day. This critical seepage velocity strongly depends on how quickly the water content and rock mass permeability decrease with decreasing temperature, or on the parameters of the rock mass freezing characteristic curve and permeability versus temperature curve. The proper setting of these parameters is a sine qua non for creating adequate mathematical models of heat and mass processes in the artificially frozen water-saturated rock mass