Cooling characteristics of LN2/CO2 composite preparation of dry ice on loose coal
In order to study the cooling characteristics of LN2/CO2 composite preparation of dry ice on loose coal and achieve the optimal combination,the visualized condensation test platform designed and built by ourselves was used to systematically analyze the effects of LN2 and CO2 on the temperature,pressure and nucleation effect of dry ice in the pipeline under different injection and delivery ratios.Based on the visual condensation test,the loose coal cooling test platform was designed and built to sys-tematically analyze the heat transfer characteristics of LN2 and CO2 during the injection stop process and the temperature inhibition effect on the loose coal temperature field under different injection and delivery ratios.The results show that LN2 is required to provide sufficient undercooling degree for CO2 condensation,when the CO2 injection and delivery volume remains unchanged,the LN2/CO2 injection and delivery ratio increases,the cooling temperature in the pipeline decreases,the pressure increases,the heat transfer efficiency of the mixed fluid of LN2 and CO2 increases,and the time of condensation is advanced.The cooling energy caused by the latent heat of phase transition has the characteristics of time-space;during the injection stage,the temperature of each measuring point in the box continues to decrease with time,the cooling rate of Plane 1 is obviously faster than that of Plane 2,and the low tem-perature area gradually expands in a conical shape.The dry ice particles accumulate in the coal seam in the recuperation stage,and continue to play the role of cooling inerting.There is a temperature differ-ence between the coal body near the injection port and the high temperature coal body for heat ex-change,and the temperature in the middle of the box gradually increases,and the temperature around the box gradually decreases until equilibrium.When the LN2/CO2 injection/delivery ratio was 4∶1,the continuous cooling capacity shows a higher level.The research results promote the deep application of dry ice phase-change cooling technology in the field of mine fire prevention.
LN2/CO2injection and delivery ratiodry icephase changefire-extinguishing perform-ance
万方数据
