地铁冻结工程按需供冷运行模式研究

Study on the Operation Mode of Cooling Energy Supply on Demand in Subway Artificial Ground Freezing

地铁人工冻结工程中存在冻结系统供冷模式单一、缺乏动态变化的问题,在施工中会造成极大的能量浪费。为此,基于单管冻结吸冷量计算模型,通过引入冻结器内盐水换热效率计算方法和群孔等效计算模型,建立适用于群孔冻结的按需供冷运行模式,实现对冻结系统制冷能力的定量求解,并通过模型试验对按需供冷运行模式进行验证。结果表明:按需供冷计算方法可有效反映冻结制冷系统运转需求的动态变化过程,且计算精度满足工程需求;冻结壁形态、土体导热系数、盐水温度等参数是影响地层吸冷量和冻结制冷系统制冷量的关键,而对于某一具体工程,冻结壁形态则是决定地层吸冷量和冻结制冷系统制冷量的关键;不同冻结孔所形成的冻结壁并不一致,如精准、合理计算整个冻结系统的按需制冷量,则应利用纵向温度求解方法或纵向测温技术对各冻结器或其各层位进行精准求解,进而利用等效代换方式进行所需制冷量的求解,试验结果显示计算误差为1.7%,满足工程精度需求。相关研究成果将为各类地铁冻结工程的冻结系统高效、低碳运转提供技术依据。

In subway artificial ground freezing projects,the freezing system’s cooling operation mode is often monolithic and lacks dynamic change,which will cause significant energy waste during construction.Therefore,based on the calculation model of the cooling capacity of the single-tube freezer,the cooling energy supply on demand operation mode for group freezing pipes was established.This mode incorporated the calculation method of heat transfer efficiency of the brine within the freezer and the equivalent calculation model of the group freezing pipes.It realized the quantitative solution for the cooling capacity of the freezing system.The results show that the cooling energy supply on demand calculation method could effectively reflect the dynamic variation in the refrigerating capacity of the freezer,with the calculation accuracy meeting engineering requirements.Parameters such as frozen wall shape,soil thermal conductivity,brine temperature are the critical factors affecting the freezing capacity of the freezer.For specific projects,the frozen wall shape is key to determining the freezing capacity of the freezer.Different freezing pipes produce inconsistent frozen walls.To accurately calculate the refrigeration capacity of the entire freezing system,the longitudinal temperature solution method or longitudinal temperature measurement technology should be used to precisely determine the conditions of each freezing pipe or each layer of the freezing pipe.Then the equivalent substitution method is used to determine the required cooling capacity.The experimental results show that the calculation error is 1.7%,satisfying the engineering accuracy requirements.The relevant research findings will provide a technical basis for the efficient and low-carbon operation of freezing systems in various subway freezing projects.