Numerical simulation study on heat tracing power of return-water hose of deep hot-water drill in polar regions

Abstract:

Deep hot-water drills in polar regions are used to melt ice by means of high-temperature and high-pressure hot water and are mainly used for rapidly drilling through the ice cap and then lowering scientific monitoring instruments or obtaining samples of the under-ice environment into it. The return-water cavity is an important part of the deep hot-water drill. After drilling， the meltwater is returned to the return-water cavity， pumped by submersible pumps， and returned to the surface through the return water hose. Due to the very low temperature of the polar regions ice and the long return hose of the deep hot-water drill， this leads to the risk of the meltwater inside the return hose being frozen during the upward return process. Therefore， laying heat tracing cables with electric heating function in the return water hose is of great significance to avoid freezing of meltwater in the return hose and stable operation of the deep hot-water drill. At present， there is no research on the required heat tracing power of return water hose. For this reason， this paper firstly analyses the normal working condition， drilling stop condition， dry burning condition and thawing condition that the return water hose may face， and then establishes the numerical simulation method of heat tracing power in four working conditions based on the COMSOL Multiphysics 6.0 software， and mainly investigates the operating power， operating time and upper limit of the safe power of the heat tracing function of the return water hose. The results of the study give the operation strategy of the return water hose heat tracing function under the four working conditions， thus providing a certain reference for the design of the return water hose heat tracing cable.

Key words:subglacial lake;hot-water drill;return-water cavity;return-water hose;heat tracing power;polar drilling