本文通过数值模拟方法(DSMC),对微纳气体在圆柱与方腔壁间导热现象及尺度效应的机理进行了探讨,通过模拟发现了热导率随尺度变大而逐渐变大并趋向于体材料,本文主要探讨了稀薄效应与受限空间对尺度效应的影响,模拟发现圆柱壁面处温度跳跃与受限空间内气体性质的改变是微纳圆柱外气体薄层导热尺度效应的根本原因. In this paper, through the numerical simulation method (DSMC), the mechanism of the thermal conductivity and scale effect of the micro-nano gas between the cylinder and the cavity wall is discussed. It is found through simulation that the thermal conductivity becomes larger as the scale becomes larger and tends to the body In this paper, we mainly study the influence of the lean effect and the confined space on the scale effect. The simulation results show that the temperature jump at the cylinder wall and the change of the gas property in the confined space are the fundamental reasons for the scale effect of thin-layer thermal conductivity of the gas outside the micro-nano cylinder.