U型或浮头式换热器管板中的热应力及其主要影响因素研究

采用有限元法研究了U型或浮头式换热器管板中的热应力，并考察了管板厚度及管壳程对流换热系数的影响。研究结果表明，对于U型或浮头式换热器，管板内仍存在较大的热应力，这是由于管板上换热管中热量传递造成的，并且当管板较厚时这种应力更为突出；在管程走热流体时，管板两侧表面存在拉伸热应力，降低管板厚度可以有效地降低由热载荷引起的管板壳程侧表面热应力，壳程侧表面热应力可由40 MPa降至-13 MPa；壳程传热系数对管板温度场的影响明显，在换热器设计中使对流换热系数较低的介质走壳程有利于降低管板的热应力。

Study of the main factors influencing the thermal stress at the tubesheet of U-tube or floating head heat exchangers

The finite element method has been employed to study the thermal stress at the tubesheet of U-tube or floating head heat exchangers, and the influence of varying the tubesheet thickness and the fluid heat transfer coefficients has been studied. It is found that for U-tube or floating head heat exchangers, thermal stress does exists at the tubesheet because of heat transfer inside the tubes embedded in the tubesheet. And for a thick tubesheet, the thermal stress is more significant. When the hot fluid flows through the tubes, the thermal stress at both sides of the tubesheet is tensile stress. Decreasing the tubesheet thickness can effectively reduce the surface thermal stress at the tubesheet on the shell-side from 40 MPa to -13 MPa. The heat transfer coefficient of the fluid on the shell-side affects the thermal stress at the tubesheet on the shell-side, and if a fluid with a low heat transfer coefficient flows on the shell-side it can reduce the thermal stress at the tubesheet.