热网换热站不锈钢换热板点蚀的临界条件

热网二级换热站一般采用板式换热器,在其使役过程中不锈钢换热板一旦出现腐蚀穿孔,不但影响一次水水质,而且干扰换热器稳定运行,甚至影响居民供热,因此阐明换热板发生点蚀的临界条件对于科学设定水质控制标准和防止点蚀发生具有重要意义。为此,通过材料化学分析、XRD、SEM及电化学测试等方法对这一问题进行研究。结果表明:在65℃条件下,304不锈钢点蚀的临界Cl;浓度为125 mg/L,316L不锈钢点蚀的临界Cl;浓度为230 mg/L;不锈钢表面一旦形成垢层,表面会发生局部酸化,此时不锈钢更容易发生点蚀;运行过程中为了防止不锈钢换热板点蚀,不仅要严格控制循环水中Cl;浓度,还应防止换热板表面结垢或附着腐蚀产物。     

Non-homogeneous Steady-State Heat Conduction Problem in a Thin Circular Plate and Its Thermal Stresses

The present paper deals with the determination of the displacement and thermal stresses in a thin circular plate defined as 0 ≤ r ≤ b, 0 ≤ z ≤ h under a steady temperature field, due to a constant rate of heat generation within it. A thin circular plate is insulated at the fixed circular boundary (r = b), and the remaining boundary surfaces (z = 0, z = h) are kept at zero temperature. The governing heat conduction equation has been solved by using an integral transform technique. The results are obtained in series form in terms of modified Bessel functions. The results for displacement and stresses have been computed numerically and are illustrated graphically.     

Calculation of Temperatures and Temperature Stresses in a Steel Cylindrical Billet with an Internal Heat Source

The solution of the problem of heat conduction and thermoelasticity of a cylinder in induction heating has been obtained with the method of equivalent sources. An example of calculation of the temperature and thermalstress fields for different grades of steel has been given.     

Distribution of Welding Stresses in a Plate with Rectilinear Weld

By the methods of conventional plastic strains and direct integration of resolving equations for stresses we obtain expressions for residual stresses in an infinite plate with rectilinear weld. The results of numerical analysis show that the three-dimensional stressed state is realized in the vicinity of the weld even for relatively thin plates.     

Influence of the Mobility of a Boundary on the Temperature Field of a Half-Space under Unstable Conditions of Heat Exchange with the Environment

Using mathematical-simulation methods, we have investigated the special features of the process of formation of the temperature field in a half-space with a boundary moving following the prescribed law in the case of realization of unstable operating conditions of heat exchange with the environment which lead to the time dependence of the heat-transfer coefficient.     

Nonlinear Photoacoustic Response on Mechanical Stresses in the Vicinity of a Hole in a D16 Aluminum-Alloy Plate

Technical Physics Letters - Characteristics of a photoacoustic signal depending on mechanical stresses in the vicinity of a hole in a D16 aluminum-alloy plate have been analyzed. A new nonlinear...     

Heat Exchange of an Experimental Module with Heat Pipes under the Conditions of Thermovacuum Tests

New dynamic thermal mathematical models in lumped and distributedlumped parameters, computational algorithms, software, results of numerical calculations, and a comparison with experiment have been presented for the heat exchange of an experimental module in the form of a threelayer honeycomb panel with uncontrolled lowtemperature heat pipes in different regimes of thermovacuum tests carried out under ground conditions.     

换热边界下梯度功能材料板瞬态热应力研究

用有限元和辛普生法,研究了由ZrO2和Ti-6Al-4V组成的梯度功能材料板的瞬态热应力问题,检验了方法的正确性,给出了对流换热边界下的瞬态热应力场分布.结果表明:材料组分的分布形状系数M、对流换热系数和环境介质温度的变化对该材料板的瞬态热应力场分布均有明显的影响;在本研究相同条件下,该材料无限自由长板在金属和陶瓷附近板内为压应力,而在板中部为拉应力.此结果为该材料的设计制备提供了准确的理论计算依据.     

冷轧薄板摩擦热及温升模型研究

冷轧时轧件塑性变形热和摩擦热是导致轧件温度升高的两个主要原因.采用包含滑动摩擦和粘着摩擦在内的预位移-滑动摩擦模型较准确地计算了轧制区摩擦热,并综合考虑轧件塑性变形热,推导了冷轧薄板温升计算公式.     

Heat Exchange in a Tube Filled with Granular Bed

Results of modeling of the process of heat transfer from a circular tube filled with granular bed with boundary conditions of the first, second, and third kind have been presented. The physical characteristics of the wall zone and the relative value of its thermal resistance have been determined based on an analysis of experimental data on the nonstationary heat exchange of the unblown granular bed. Recommendations on calculation of the heat exchange at elevated temperatures have been given.     

Temperature Stresses in a Functionally Graded Cylindrical Shell

Materials Science - For functionally gradient isotropic circular cylindrical shells, we propose the nonstationary heatconduction and thermoelasticity equations with appropriate boundary conditions....     

Calculation of a Three-Dimensional Temperature Field with Allowance for the Radiation Heat Exchange in Chambers of Tubular Ovens with Acoustic Burners

A three-dimensional calculation of the heat transfer in the chamber of a technological tubular oven with the combustion of methane in air with acoustical burners of a floor flame has been carried out. The calculation method is based on the joint numerical solution of the difference analogs of the three-dimensional equations of radiation, energy transfer, and turbulent motion of flue gases and the model of methane combustion in air. The entire spectral region is divided into six bands to account for radiation selectivity. The organization scheme of three-dimensional modeling of the burner operation is shown. Some results of numerical studies of heat and mass transfer in a combustion chamber are given.