ANALYSIS OF METHODS FOR CALCULATING HEAT TRANSFER BETWEEN BRINE IN THE FREEZING PIPES AND SURROUNDING SOILS

Abstract

The relevance of the study follows from the high demand for artificial freezing of soils in sinking vertical mine shafts. Analysis of methods for calculating heat transfer between brine in freezing columns and surrounding soil makes it possible to further improve the methods for calculating heat transfer coefficients. The research results will be useful for designing freezing systems in shaft construction. The main aim of the research is to analyze the existing methods for calculating heat transfer between the coolant in the freezing column and the surrounding rocks, to determine the main ways to further improve the methods for calculating heat transfer in conditions of coaxial freezing columns Objects: the system «brine – freezing pipe – frozen soil». Methods: comparative analysis of existing methods for calculating heat transfer, numerical simulation in the Ansys Fluent software package. Results. The authors have carried out the comparative analysis of the existing approaches and methods for calculating the heat transfer coefficient through the wall of the freezing pipe between the brine (coolant) moving along it and the frozen soil. The paper describes the reasons for discrepancy between the results when using various methods for calculating heat transfer. The authors have carried out the comparative analysis of the heat transfer coefficients obtained by various calculation methods, as well as as a result of numerical three-dimensional modeling of the brine flow. The drawbacks of the existing methods for calculating heat transfer are shown and the main ways of further improving the methods for calculating heat transfer under conditions of coaxial freezing columns are determined: taking into account heat transfer between the forward and reverse brine flows in the freezing columns, analyzing the effect of transient velocity and temperature fields in the reverse brine flow at the initial section of the freezing column (near the column shoe), analysis of the sensitivity of the value of the heat transfer coefficient to deviation from the alignment of the supply and freezing pipes.

Keywords

• frozen wall
• artificial freezing
• indirect freezing
• heat transfer
• freezing pipe
• brine
• heat transfer coefficient