The freezing method is accomplished by the principle of heat absorption during vaporization of a refrigerant (usually liquid ammonia). The refrigeration process consists of three major cycles.
Ammonia circulatory system
The liquid ammonia evaporates into saturated steam in the evaporator, and absorbs the heat of the surrounding brine. The saturated steam ammonia is compressed by the ammonia press into superheated steam, cooled by the condenser to high-pressure saturated liquid ammonia, and then decompressed by a throttle valve. The low pressure liquid ammonia re-flows into the evaporator to vaporize.
2. Brine circulation system Brine is used as a refrigerant. After taking the cold amount from the brine tank outside the evaporator, the brine pump is drained through the brine main pipe, the liquid distribution ring and the liquid supply pipe into the bottom of each freezing pipe, and then the annular space between the freezing pipe and the liquid supply pipe is taken. The bottom-up flow, and absorb the heat of the surrounding rock formation, so that the rock layer is cooled and frozen, and the rising brine is returned to the brine tank of the freezing station via the liquid return pipe, the liquid collecting ring and the salt water main pipe.
3. Cooling water circulation system The cooling water in the condenser needs to flow continuously to form a circulation, and the heat of the superheated ammonia vapor is taken away.
The thickness of the frozen wall and the diameter of the frozen hole arrangement circle are calculated according to the construction and personal safety of the frozen section during the excavation period
. The spacing of the freezing holes is 1.2m~1.4m .
The permanent well wall of the wellbore is constructed by the freezing method. Due to the large ground pressure and water pressure, the construction conditions are bad, and the connection is too much, the well wall structure has been developed from a shallow single-layer well wall to a double-layer well wall and a sandwich well. Wall and composite wall of various materials, etc.


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