Key parameters and optimal design of a single-layered induction coil for external rapid mold surface heating

Setting high mold temperatures for injection-molding plastics facilitates favorable flow conditions for filling cavities with melted materials and provides an esthetically pleasing surface as well as a high replication rate of high-quality products; however, the cooling times are typically prolonged. Electromagnetic induction heating incorporating surface heating instead of conventional volume heating for mold-heating processes is advantageous because it provides a rapid heating time and a reduced cooling time, is environmentally friendly, and saves energy; therefore, it has been adopted in various variotherm injection-molding systems. Although previous studies have discussed how induction heating is influenced by major factors, such as the number of coil turns, working frequency, and heating distance, few studies have investigated other crucial factors, such as the thickness of the heated target and the position of the induction coil. In this study, the effects of the thickness of a heated target, pitch of coil turns, heating distance, position of the induction coil, working frequency, and waiting time on the heating rate and temperature uniformity of induction heating on a mold surface by using a single-layered coil were analyzed. In addition, the Taguchi method and principal component analysis were applied to determine the optimal combination of control factors for achieving a high heating rate and low temperature deviation. Both simulation and experimental results indicated that the thickness of a heated target plays a crucial role in affecting the heating rate; specifically, a thicker workpiece slows the heating process and generates rapid heat dissipation after induction heating. Moreover, the position of the induction coil exerts the most notable effect on heating uniformity.     

Enhancement of induction heating efficiency on injection mold surface using a novel magnetic shielding method

Mold temperature is a major factor in the quality of injection molding process. A high mold temperature setting is feasible to enhance the molding quality but prolongs the cooling time. Induction heating is the method currently used to heat the mold surface without increasing the molding cycle. However, one unresolved problem of induction heating is the proximity effect resulting from two adjacent coils with different current directions. The proximity effect substantially decreases heating efficiency, which then causes non-uniform heating. This effect is difficult to avoid in a single-layer coil. The most common solution, which is to use magnetic concentrators to reduce the proximity effect, does not obtain satisfactory results. In the novel magnetic shielding induction heating method developed in this study, heating efficiency and temperature uniformity are enhanced by using ferrite materials to separate the conflicting magnetic fields caused by the repulsive proximity effect. Three typical single-layer coils are investigated in this study, including a reciprocated single-layer coil, a single-layer spiral coil, and a rectangular frame coil. Appropriate placement of ferrite materials on these induction coils successfully eliminated the proximity effect, increased the heating rate, and improved temperature uniformity.     

Comparison between the steady-state performance of self-excitedreluctance and induction generators

A comparison of the steady-state performance of self-excited reluctance and induction generators is presented. Segmental and salient-rotors are built to suit the stator of a three-phase induction machine. The machine is operated in the two modes of generation. Results from computer models for no-load and load conditions are confirmed with experimental results. The results of the two generation modes are compared. It is shown that the reluctance generator has an equal chance of being used for wind-power generation. In addition, it has the advantage of operating at a fixed frequency. Although both types of rotors may be used, better performance is obtained from segmental-rotors     

Numerical analysis and thermographic investigation of induction heating

Induction heating process was investigated numerically and experimentally. Cylindrically shaped steel workpiece was heated with different heating protocols. Numerical model with coupled electromagnetic and thermal physical phenomena was solved using the finite element method. Temperature-dependent and temperature-independent steel material properties were considered and their impact on simulation results was evaluated. Simulation results were also compared with experimental measurements using an algorithm for processing thermographic images. Good agreement between them was obtained for workpieces without defects. With ability to observe temperature distributions and material defects, the thermographic camera demonstrated to be an effective non-contact measurement tool and suitable alternative to thermocouples.     

Nonplanar mold surface heating using external inductive coil and magnetic shielding materials

A set of three-dimensional steady-state finite element numerical simulations of temperature distributions was performed for various coil geometries with and without magnetic shielding materials on a nonplanar mold plate surface subjected to induction heating. The surface was used for fabricating a miniature automotive spoiler. A comparison between the simulated and experimental results showed that the location of the inductive coils relative to the processed workpiece remarkably influenced the temperature distribution and heating efficiency. In particular, the proximity effect, which leads to nonuniform heating along the workpiece wall, was ameliorated by introducing magnetic shielding materials on the coil design.     

感应加热的电磁力再分析

应用感庆加热中电流的互关系和能量定律，借助相应简易公式分析电磁力的大小、方向、作用点及主要影响因素。     

感应加热炉炉衬材料

介绍适合于感应加热设备使用的新型耐火材料XL001的性能,感应器绝缘的处理方法。这种新材料成本低,成型工艺简便,使用寿命长。     

Flow and heat transfer in curved wall jets on circular surfaces

Consideration is given to curved wall jets (i.e. flow along a wall which is curved in the streamwise direction) and, in particular, to flow along either a convex or a concave circular surface. The laminar flow and heat-transfer characteristics are investigated by making use of the method of inner and outer expansions. The Navier-Stokes and energy equations are expanded in series, with as the expansion parameter. The first-order equations are identical to the conventional boundary-layer equations, whereas the second-order equations are corrections for curváture and displacement effects. The latter equations were solved by a difference-differential method, with Pr = 0·72 for the energy equation. The second-order correction increases the wall shear, the extent of the increase being greater for flow over a concave surface than for flow over a convex surface. On the other hand, the second-order correction either increases or decreases the Nusselt number, depending on whether the surface is convex or concave. The Coanda effect, whereby an induced transverse pressure difference inhibits flow separation, was demonstrated by the analysis.     

Simulation of droplets impact on curved surfaces with lattice Boltzmann method

Several dimensionless parameters are studied to describe their effects on the deformation of a droplet after impact on a 2D round surface by using lattice Boltzmann implementation of pseudo-potential model. Four typical deformation process can be found: moving, spreading, nucleating and falling. In addition, in some special cases, part splashing is involved. It is observed that impact velocity of droplet has a significant influence on the droplet impacting dynamics. With the increasing of the impact velocity, different states have been found during the process. Moreover, when the surface is hydrophobic, splash occurs.     

中频感应加热在锻造上的应用

本文介绍曲轴连杆厂采用中频感应加热炉对锻件进行锻前加热,有诸多的优点:如效率高,生产准备时间缩短,工作环境得到改善,锻件的表面和内在的质量提高了,节能显著等。建议在供电条件允许的情况下,锻造加热应优先考虑中频感应加热。     

Comparison of the optimal performance of single- and two-stage thermoelectric refrigeration systems

The cycle models of a single-stage and a two-stage semiconductor thermoelectric refrigeration system are established, based on non-equilibrium thermodynamics. They are used to derive the general expressions of three important performance parameters, such as the coefficient of performance (COP), the rate of refrigeration, and the power input. By using these expressions, the performance of the two-stage thermoelectric refrigeration system is discussed in detail. The maximum COP and rate of refrigeration are calculated, the internal structure parameter of the thermoelectric device is optimized, and the reasonable ranges of some parameters are determined. The results obtained here are compared with those of a single-stage thermoelectric refrigeration system, and consequently the advantages of two-stage thermoelectric refrigerators are expounded.     

中频加热设备与应用

本文详述ＧＴ－５０－２．５输油管体感应加热设备的结构、性能、特点及其应用。     

肝癌介入治疗对靶血管损害的影像学评价及预防

本文回顾分析具有完整血管造影记录的263例肝癌介入治疗病例,采用介入治疗前后自身比较的方法评价靶血管近段的形态变化,观察其受损情况。结果发现:受损血管共85支,总受损率为32.2％,明显高于文献报道的单次血管造影和介入治疗所致的靶血管受损率。其中17.0％的损害导致选择性插管发生困难或失败,引起肿瘤侧枝循环形成而影响了介入疗效.受损血管的形态学改变可分为五类:1.毛糙或小波浪状(7.2％);2.局限性环形狭窄(14.8％);3.细线样狭窄(3.0％);4.串珠样狭窄(4.6％);5.完全闭塞(2.6％)。本文讨论了引起血管损伤的原因以及与受伤后的血管外形改变的关系，并提出了预防和减少血管损伤的方法和意见。     

Incineration of diesel particulate matter using induction heating technique

Incineration of diesel particulate matter for the regeneration of a mesh-type particulate-filter is achieved using induction heating technique. Heating of the diesel particulates deposited on the mesh-type particulate-filter at around 600 °C is investigated. In the case of the particulate filter, stainless-steel mesh-type filters are considered and the influence on filtering efficiency, the engine performance due to back-pressure generation is studied. Theoretical estimation shows that induction heating approach for the regeneration via exhaust gas heating requires high power (>3 kW). On the other hand, regeneration of mesh-type particulate-filter using induction heating technique requires a low input power of around 0.5 kW in the off-line condition. The proposed mesh-type particulate-filter allowed a filtration efficiency of around 30–40% at lower engine speeds and part loads. Particulate combustion through induction heating at static condition is studied and power required for mesh-type filter and sintered metal filter regeneration during engine operation is estimated theoretically.     

Feasibility evaluation of gas-assisted heating for mold surface temperature control during injection molding process

Dynamic mold surface temperature control has the advantage of improving molded part qualities without significant increases in cycle time. In this study, a gas-assisted heating system combined with water cooling and different mold designs to achieve dynamic mold surface temperature control was established. The feasibility of using gas-assisted heating for mold surface temperature control during the injection molding process was then evaluated from experimental results. The effect of mold design as well as heating conditions including hot gas temperature, gas flow capacity, and heating time on the heating efficiency and the distribution uniformity of mold surface temperature were also studied. Results showed that as hot gas temperature and gas flow capacity increased, as well as increasing heating times from 2 s to 4 s, mold surface temperature increased significantly. Fan shaped gas channel design exhibits better mold surface temperature distribution uniformity than tube shaped gas channel design. During gas-assisted heating/cooling, it takes 2 s to increase mold surface temperature from 60 °C to 120 °C and 34 s for mold surface to return to 60 °C. In addition, under specified heating conditions and using the best composite mold designs, the heating rate can reach up to 30 °C/s, a rate well-suited to industrial applications.     

Comparison of activated carbon prepared from Jatropha hull by conventional heating and microwave heating

An attempt to compare the yield and porous nature of the activated carbon prepared using the conventional and microwave assisted heating, is the focus of the present work. Towards this Jatropha hull (a biomass precursor) is activated using the popular activating agents, steam and CO₂ to assess the relative merit of activating agents and the heating methods. The process optimization exercise is carried out with the minimum number of experiments following the standard full factorial statistical design of experiments (RSM). The activated carbon prepared under the optimized conditions is compared based on the yield and porous nature. The yield of activated carbon is not found to vary significantly for the steam activation, irrespective of the heating method, while it is found to double using CO₂ activation with microwave heating as compared to conventional heating. The pore volume and the surface area is found to double using the microwave heating with steam, while it is found to be of the same order of magnitude using CO₂ activation. Although the porosity of carbon is of the same order of magnitude using CO₂ activation, the activation temperature, the activation time, CO₂ flow rate are significantly lower than the conventional heating rendering the process more economical than the conventional heating. The steam-carbon reaction rate is significantly higher than the carbon-CO₂ reaction rate, rendering the time requiring for activation lesser using steam activation as compared to CO₂ activation.     

Dynamics and shape of bubbles on heating surfaces: A simulation study

The bubble shape on heating surfaces is simulated by numerically solving the Young–Laplace equation including a dynamic pressure term. This dynamic pressure is calculated by a correlation involving several empirical coefficients. By adjusting these coefficients, a given bubble shape can be well represented. Thus the pressure around the bubble and various forces acting on the bubble can be accurately calculated. Some calculation examples are given. The results show an important effect of dynamic forces on the bubble shape. Therefore, the assumption of spherical bubbles could lead to big errors in force evaluations.     

低温地板辐射供暖节能作用分析

低温地板辐射供暖地板与外围护结构内表面存在辐射换热，散热器供暖房间的散热器附近以及散热器上部热气流与外围护结构存在热流短路。文章在低温地板辐射供暖室比散热器供暖房间室内设计温度降低2℃的情况下，分别对三个典型地区这两种供暖方式在上述情况下造成的房间热负荷和供暖季平均耗热量进行计算。结果表明此条件下，低温地板辐射供暖房间的热负荷可降低10％～15％，节能率约为15％～20％。     

Radiative CNT-based hybrid magneto-nanoliquid flow over an extending curved surface with slippage and convective heating

This study concentrates on the hydrothermal prominence of a mixed convective flow of a hybrid nanoliquid over a convectively heated extending curved surface under the influence of a uniform transverse magnetic field. Two types of carbon nanotubes (CNTs), namely single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), and magnetite nanoparticles are dispersed in the host liquid (water) to simulate the hybrid nanoliquid flow model. First- and second-order velocity slip conditions and nonlinear radiative heat flux are incorporated in this model. First, the system of governing partial differential equations is changed into nonlinear ordinary differential equations through the utilization of appropriate transformations and computed numerically via MATLAB built-in function bvp4c based on the three-stage Lobatto IIIA technique. The consequences of physical and geometrical parameters pertinent to this analysis on the dimensionless physical quantities of interest are deliberated using requisite graphs and tables. Our simulation communicates that the first-order velocity slip parameter decreases the velocity profile, whereas the second-order velocity slip parameter is found to be augmented. The suspension of CNTs in the magnetite nanoliquid improves the local surface drag force but diminishes the local heat flux. Moreover, it is examined that SWCNTs have greater impacts than MWCNTs.     

Analysis of entropy generation during natural convection in porous enclosures with curved surfaces

The natural convection is analyzed via the entropy generation approach in the differentially heated, porous enclosures with curved (concave or convex) vertical walls. The numerical simulations have been carried out for various fluids (Prandtl number: Pr_m?=?0.015, 0.7, and 7.2) at various permeabilities (Darcy numbers: 10^?5?≤?Da_m?≤?10^?2) for a high value of Rayleigh number (Ra_m?=?10⁶). The finite element method is employed to solve the governing equations and that is further used to calculate the entropy generation and average Nusselt number. The detailed spatial distributions of S_θ and S_ψ are analyzed for all the wall curvatures. Overall, the case with the highly concave surfaces (case 3) is the optimal case at low Da_m, whereas the cases with the less convex surfaces (cases 1 and 2) are the most efficient cases at high Da_m.