地下换热器温变模式对其冻胀作用的影响

Influence of Temperature Mode on Frost Heave Action of Ground Heat Exchanger

为研究地下换热器的低温运行模式对其冻胀变形影响,通过建立管土结构冻胀实验系统,选择连续降温、恒温、大幅度和小幅度周期性变温4种运行模式,采用冻结半径追踪和管体应变测量方法,研究了岩土温度、冻结区发展、换热管受力以及变形特性。结果表明:连续降温模式可产生最大的冻结范围,周期性变温模式的最大冻结范围大于恒温模式;连续降温模式可产生最大的岩土冻胀力,恒温模式次之,周期性变温模式最小;各模式下的换热管均发生椭圆化变形,椭圆化短轴位于进、出水两管中心连线方向,管体变形程度与冻胀力相对应,周期性变温可减轻管体变形;但变温幅度的作用效应有限。可见在实际工程中,应采取措施避免换热管连续降温,在长时间低温运行后,应及时通过升温来减缓管体受力变形的危害。

In order to study the influence of temperature mode on ground heat exchanger s frost heave and deformation,the pipe-soil structure frost heave experiment system was set up.Four different temperature modes were implemented and contrasted,which included continuous dropping temperature mode,constant temperature mode,large and small periodic temperature changes mode.During the experiment,the freezing radius tracking and pipe surface strains measuring were carried out to investigate the soil temperature,the freezing area development,the stress and deformation on pipe.The results show that,among the four temperature modes,the continuous dropping temperature mode can bring the largest freezing area,the maximum freezing range of the periodic temperature changes mode can be larger than that of the constant temperature mode;the continuous dropping temperature mode can bring the largest soil frost heave force,the constant temperature mode is followed by the periodic temperature changes mode;elliptical pipe deformations are shown in every mode,the minor axis of elliptical pipe is in the connecting line of inlet and outlet pipe centers,the degree of pipe deformation corresponds to the frost heave force in every mode,the pipe deformation can be reduced by the periodic temperature changes,but the effect of temperature change amplitude is limited.It is concluded that measures should be taken to avoid continuous dropping temperature mode in heat exchange pipe,timely heating can be used to alleviate the pipe deformation after running at low temperature for a long time.