Research On Cooling Mechanism And Key Parameters Of Cold Wall Cooling System In High Temperature Mines

In order to solve the common heat damage in high temperature mine,a cold wall cooling technology is put forward.The working principle is as follows.Firstly,the heat absorption plate with the cold medium is attached to the wall of the roadway for heat exchange with the rock wall of the roadway and ventilation airflow.Then,the absorbed heat is transferred to the flowing cold medium to reduce the heat from high-temperature surrounding rock to roadway,and thus decreasing the temperature in mine.Different from other cooling systems in mines,the cooling principle of cold wall cooling system includes four aspects,that is,endothermic cooling,convection cooling,heat insulation cooling and radiation cooling.In this thesis,the research is carried out from the following aspects.The working model of cold wall cooling system is proposed,and mainly composed of refrigerant system,refrigeration system,transport system and cold wall system.According to the actual conditions,the cold medium is prepared by the natural cooling of subterranean thermostatic layer and artificial refrigeration system.The heat absorption characteristic parameters of heat absorption plate are studied by experimental and numerical methods.Simultaneously,the experimental platform of small-scale cold wall cooling system is established to study the function relationships of the temperature rise of water flow in heat absorption plate and heat absorption efficiency of heat absorption plate with the water flow rate(0.024kg/s?0.064kg/s),heat flux of electric heating film,and the inlet water temperature(19??29?),respectively.Moreover,the Fluent software is used to calculate the function relationships of the temperature rise of water flow in heat absorption plate with the water flow rate(0.0018kg/s?0.0353kg/s),the inlet water temperature(2??22?),the roadway wall temperature and the distance between pipes,respectively.The governing equation of heat absorption of the cold wall cooling system is established,and then its analytical solution is worked out by section iterative method and variables separation method.Based on these,the heat dissipation density of the surrounding rock and the average heat absorption density of the system can be figured out.The computing method of average ambient radiation temperature in the roadway is modified by the normalization method,and then the Monte Carlo method is used to calculate the radiation angle coefficient.It is shown by comparing the theoretical solution with numerical solution of the radiation angular coefficient that when the number of energy beams reaches five million,the maximum calculation error of Monte Carlo method is only 0.13%.Finally,the design process of cold wall cooling system is put forward by an engineering case,and then the key design parameters such as water flow rate of the cold wall cooling system in mine with heat damage are obtained.The calculation results show that the cold wall cooling system can make the dissatisfaction rate of miners with the moderate working intensity decrease from 92% to 27%.