Heat transfer in a two-phase closed thermosyphon working in Polar Regions

The observed influence of ambient air temperature on ground temperature in the Far North is an urgent problem as excessive warming of the ground may cause permafrost thawing and structural instability of the built environment. A promising solution is to use thermosyphon-based cooling systems for thermal stabilization of the ground surrounding the piles or other supporting elements of special constructions in the Far North. In this work, we experimentally studied the influence of air and ground temperatures and heating surface temperature that simulates the operation of heat-loaded equipment on the mechanisms of the condensate formation in a thermosyphon. We determined the effect of the thermosyphon operation on the change in ground temperature in the Far North and found the possibility of operation of the thermosyphon-based cooling system at air temperatures in the range of 4–10 °C. In addition, it was found that with an increase in the ambient air temperature from 4 to 10 °C, the ground temperature increased by 5–5.5 °C without the thermosyphon and by 3.1–4 °C with the thermosyphon. The operation of the thermosyphon in the ground layer made possible a two-fold reduction at least of its temperature, not only in close vicinity of the evaporation section, but also at a depth exceeding the height of the thermosyphon evaporation section. We also showed that there are two condensation modes (drop-streak and film-streak) when the heat flux supplied to the lower cover was between 0.7 and 5.1 kW/m2, and the condensation section was cooled due to natural convection.