Paraffin-CaCl₂·6H₂O dosage effects on the strength and heat transfer characteristics of cemented tailings backfill

The challenge of high temperatures in deep mining has remained harmful to the health of workers and their production efficiency. Adding phase change materials to filling slurry and using the cold storage function of these phase change materials to reduce downhole temperatures was shown to be an effective approach to alleviate the aforementioned problem. Paraffin-CaCl₂·6H₂O composite phase change material was prepared in the laboratory. The composition, phase change latent heat, thermal conductivity, and cemented tailings backfill (CTB) compressive strength of the new material were studied. Its heat transfer characteristics and endothermic effect of the phase change material were simulated using Fluent software. The results showed the following: (1) The new paraffin-CaCl₂·6H₂O composite phase change material improved the thermal conductivity of the native paraffin while avoiding the disadvantageous water solubility of CaCl₂·6H₂O. (2) The calculation formula of the thermal conductivity of CaCl₂·6H₂O combined with paraffin was deduced，and the reasons were explained in principle. (3) The “enthalpy–mass scale model” was applied to calculate the latent heat of phase change of nonreactive composite phase change materials. (4) The addition of the composite phase change material Paraffin-CaCl₂·6H₂O reduces the CTB strength but increases its heat absorption capacity.