黄土高原地区土壤分层与未分层地埋管埋深优化研究

为了研究黄土高原地区土壤分层与未分层地埋管埋深的最优值。本文使用Fluent仿真软件建立单U型地埋管三维模型,分析土壤分层与未分层两种情况下,埋深分别为60 m、70 m、80 m、90 m、100 m地埋管出口温度和换热量的变化规律,从而确定地埋管的最优埋深。结果表明:地埋管的埋深对于整个系统的出口温度和换热量影响显著,埋深越深地埋管的换热性能越好,但随着地埋管埋深的增加,两者增长幅度逐渐降低;土壤分层情况下的地埋管进出口温差和单位井深换热量大于土壤未分层情况下的进出口温差和单位井深换热量,且差距明显;在土壤分层情况下,埋深从60 m到70 m时,进出口温差最大为0.17℃,换热量变化率为0.12;在土壤未分层情况下,埋深从70 m增加到80 m时,进出口温差最大为0.15℃,换热量变化率为0.13。综合考虑地埋管的出口温差和总热量变化率,单U26管,土壤分层地埋管最优埋深为60~70 m,土壤未分层地埋管最优埋深为70~80 m。该研究结论可为黄土高原地区或同类地貌下地源热泵单U形地埋管埋深提供数据支撑和理论参考。

Microstructures and mechanical properties of electroplated Cu-Bi coatings

Electroplating has been used to produce Cu-Bi coatings. The crystal structure and lattice parameters of Cu in Cu-Bi composite coating were measured and compared with Cu coating. The mechanical properties of the coatings were also studied. It was found that the deposition parameters have significant effect on the mechanical properties of the Cu-Bi coatings. The microhardness has been improved from HVso165 of Cu coating to HVs0 250 of Cu-Bi composite coating prepared at 50 mA/cm2 for 20 min. Correspondingly, wear resistance of the Cu-Bi composite coating has also been enhanced significantly.