A
thermal analysis has been performed for designing a thermo-mechanical ice coring
drill. The drill consists of a fiberglass core barrel with cutter at the tip,
where water is provided as a cutting fluid. The heat transfer in a cylindrical
ice core has been evaluated to estimate the time of drilling. The model was built
upon a complete range of temperatures of the ice core varying from -50oC to 0oC.
Cutting rates of ice varied from 5.56×10-4 m/sec to 16.7×10-3 m/sec based upon
field data of brittle and ductile ice respectively. This rate determined the drilling
fluid circulation rate and gave rise to a range of the convective heat transfer
coefficients. This study was conducted for one typical value of convection heat
transfer coefficient, arising from the circulation of the warm fluid around the
core barrel at 140 W/m2K. Results of one-dimensional radial conductive heat transfer
in the ice core were employed in the design. The two dimensional heat conduction
problem of the ice core under different boundary conditions was also studied and
discussed in this paper. The results provide guidelines to drillers in the field
on how long they can drill before melting the surface of the ice core due to the
warming influence of the cutting fluid. |
