| With the development of economy and living standard,the demand for energy in the world is increasing.Coal dominates the current energy supply in China,and miners are still faced with the dangers caused by various accidents in underground coal at any time.Mine refuge chamber is a room where can provide miners a safe place after the mine disaster.Because of the possibility of gas escaping from the mine,the power system must be cut off to avoid the second explosion,which makes the cooling demand of the closed chamber difficult to meet in the conventional way.At present,there are many defects in the four cooling methods used in the refuge chamber.Although the relevant researchs aim to improve the conventional cooling methods,it is still difficult to meet the requirements of safety,reliability and stability at the same time.In this dissertation,a new coupling cooling method of latent heat thermal energy storage(LHTES)combined with pre-cooling of the envelope(PE)was proposed.Based on this method,firstly,the heat transfer mechanism of surrounding rock in deep buried tunnel was studied,and then,the theory of intermittent cold storage was put forward.Secondly,the model of coupled cooling system was set up,and based on that,the influences of different factors on the temperature control process were analyzed.Finally,the cooling system was optimized.The coupled cooling method presented in this dissertation requires no maintenance,no power,and the system is safe and reliable with simple structure,which solves the cooling problem of refuge chamber with intrinsic safety.An acceptable temperature environment is provided for the trapped minners in refuge chamber,which plays an important role in alleviating the tension of miners and increasing the rescue probability.According to the time order,the coupled cooling method of LHTES combined with PE contain two parts: the PE period and the temperature control period.A more simple and complete expression of temperature distribution of surrounding rock was firstly given by the use of integral transform method.The dimensionless expression was also given to reveal the influence of dimensionless quantities on the temperature distribution in the surrounding rock.Then the calculation program is written by using Matlab,and the parameters which were required in the numerical calculation were firstly determined.Furthermore,the engineering calculation formula of storage capacity of surrounding rock was deduced,which greatly facilitates the engineering calculation process.Based on the engineering calculation formula,the influence of the factors including the parameters of surrounding rock and the air supply was analyzed,and the better parameters were choosen for practical application.Based on the analysis of the operating characteristics of PE,it is found that the cold storage capacity of surrounding rock gradually decreases in the long-term process.Thus,the combined strategy of continuous / intermittent mode for the whole PE process is suggested firstly.In the current study,a simplified numerical model for the intermittent cold storage of the surrounding rock is established.The influence of the intermittent period and intermittent ratio on the cold storage performance in refuge chamber is investigated in detail.According to the engineering requirements in different periods,a sectional combined intermittent energy storage mode is put forward with fast,energy-saving and convenient aims.The main parts of the coupled cooling system in the temperature control process include the surrounding rock,the indoor heat source,the air and the phase change meterials(PCM)cooling devices.The heat transfer among the inner surface of the surrounding rock,the indoor air and the phase change cooling device is a coupled process,so the unified calculation should be carried out.The scale of the heat transfer range of the surrounding rock is large,while which of the PCM cooling devices is very small.Besides,there is a complex heat transfer process of conduction,convection and melting in PCM,so the whole field model can not be calculated under the existing conditions.To solve this problem,a numerical model,which takes the non-form PCM cooling device as the main model and the surrounding environment as the auxiliary model,was proposed.This numerical model takes both of the precise solution of the PCM cooling device and the whole solution into account and greatly reduces the computation time,and the experiment was carried out to verify the model.To save the living space,the PCM cooling device canbe set as phase change plates(PCP)hanging on the wall or phase change chairs(PCC).Numerical models were established for different PCM cooling devices.For the coupled cooling system based on PCP,the evaluation index of thermal endurance time was established,and the influence of cold storage temperature,melting temperature,size and number of PCP on chamber temperature control was analyzed.For the coupled cooling system based on PCC,a new coupled cooling model was established,and the temperature control effect was studied.The results found that the coupled cooling system implementing PCP can effectively control the chamber temperature within 35 ℃ in 96 hours,but there exists strong mismatch in time between the discharging rate of PCP and indoor load.It is suggested that the heat transfer of the whole process should be taken into account using the coupled cooling method,and the parameters of the system should be optimized.The coupling cooling method implementing PCC saves more living space,but only can make the indoor temperature not exceed the control temperature in 40 hours.So it is necessary to combine with the PCP to achieve the control requirements.Finally,the coupled cooling systems implementing PCP or PCC were optimized seperatly for the insufficient of temperature control in mine refuge chamber.Considering the influence of various factors of different cold storage temperatures,the optimization schemes were put forword to achieve the purpose of temperature control and cost reduce.On this basis,the two optimal cooling results and configurations were compared,which provides a reference for the practical application of the cooling method. |
