共查询到20条相似文献,搜索用时 15 毫秒
1.
Shia-Chung Chen Rean-Der Chien Su-Hsia Lin Ming-Chung Lin Jen-An Chang 《International Communications in Heat and Mass Transfer》2009,36(8):806-812
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. 相似文献
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Jung-Chang Wang Ai-Tsung LiYu-Pin Tsai Ray-Quen Hsu 《International Communications in Heat and Mass Transfer》2011,38(2):179-183
This paper aims to use the local heating mechanism, along with the excellent thermal performance of vapor chamber, to analyze and enhance the strength of products formed after insert molding process. In the insert molding process, the metal insert is firstly placed into the mold, and then formed into an embedded plastic product named diving regulator by injection molding. These results indicate that, the product formed by the local heating mechanism of vapor chamber can reduce the weld line efficiency and achieve high strength, which passed the standard of 15.82 N-m torque test, with a yield rate up to 100%. 相似文献
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Shia-Chung Chen Hai-Mei Li Shyh-Shin Hwang Ho-Hsiang Wang 《International Communications in Heat and Mass Transfer》2008
Microcellular injection molding (also known as Mucell process) with supercritical fluid (SCF) content is capable of producing parts with excellent dimensional stability while using less material, lower injection pressure, and achieving a shorter cycle time. However, most of microcellular processing studies were done on interior morphology, microstructure of the microcellular products, researches and reports on the splay-like appearance, or even a rougher swirl surface which is the restriction for the application of the microcellular injection molding are insufficient. This study investigates the influence of mold temperature on the surface roughness of Polyethylene terephthalate (PET)/Polycarbonate (PC) parts molded by hybrid filming–microcellular injection processing. The PET film is considered as a passive mold temperature controller because of its lower heat transfer coefficient (0.16 J/kg °C) compared with mold base steel of 31.5 J/kg °C. Temperature field changes of mold base caused by different film thickness (0.125 mm, 0.188 mm) were analyzed. The surface roughness of microcellular parts with/without film was measured by a 3D laser microscope. It was found that surface toughness decreases while film thickness increases with minimum surface roughness 1.8 μm. Compared with conventional mold temperature (60 °C), the hybrid molded parts with 0.125 mm film lowered surface roughness from 26 μm to 5.6 μm, to 1.8 μm of 0.188 mm film. And the hybrid processing also improved the uniformity of foamed parts surface quality by eliminating swirl and even surface roughness. 相似文献
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Shia-Chung Chen Hai-Mei Li Shih-Tsun Huang Yi-Chao Wang 《International Communications in Heat and Mass Transfer》2010
In-mold decoration (IMD) during injection molding is a relatively new injection molding technique and has been employed for plastic products to improve surface quality and achieving colorful surface design, etc. During IMD processing, the film is preformed as the shape of mold cavity and attached to one side of the mold wall (usually cavity surface), then molten polymer is filled into the cavity. Heat transfer toward the mold cavity side during molding IMD part is significantly retarded because the film is much less thermal conductive than metal mold. To investigate the effect of film on temperature field, polycarbonate (PC) was injection molded under various conditions including coolant temperature, melt temperature, film material and film thickness. Simulations were also conducted to evaluate the melt–film interface temperature and its influence from film initial temperature and film thermal properties. For PC film, it was found that the heat transfer retardation results in the mold temperature drop in cavity surface and the maximum temperature drop as compared to that of conventional injection molding without film may be as high as 17.7 °C. For PET film, this maximum mold temperature drop is about 13 °C. As PC film thickness increases, the retardation-induced mold temperature difference also increases. The initial film temperature (30 °C and 95 °C) may affect the melt–film interface temperature at the contact instant of melt and film by about 12 °C to 17 °C. When thermal conductivity of film increases from 0.1 W/(m–k) to 0.2 W/(m–k), melt–film interface temperature may vary by 22.9 °C. The simulated mold temperature field showed reasonable agreement with experimental results. 相似文献
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Flow injection in center-gated disks is numerically studied in this paper for possible applications in the manufacturing of composite materials in microgravity environment. The numerical method, which combines the finite element method with a predictor/corrector scheme, is used to determine the transient flow field. The effects of gravitation and surface tension on the development of flow front profile and velocity field are examined for a wide range of the governing parameters (namely, the capillary and Bonds numbers). It has been found that surface tension tends to hold the flow front in symmetric shape while gravitation is to distort it. The balance of these two forces has significant effects on the front shape, front tip traveling speed and required injection pressure. Good agreement is found between the numerical prediction and the experimental results concerning the advancement of the flow front and the front shape. The present results provide useful information in the design of resin transfer molding process in space. 相似文献
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The performance of an isothermal endoreversible two-reservoir chemical pump, in which the mass transfer obeys diffusive law, is analysed and optimised in this paper. The relation between the rate of energy pumping and the coefficient of performance of the isothermal chemical pump is derived by using finite-time thermodynamics. Moreover, the relation between the minimum power input and the coefficient of performance, and the relation between the minimum entropy production rate and the rate of energy pumping are obtained. The results obtained herein can provide some new theoretical guidelines for the optimal design of a class of apparatus such as mass exchangers, as well as electrochemical, photochemical, solid-state devices, and the fuel pumps for solar-energy conversion systems. 相似文献
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Natural convection driven by combined thermal and solutal buoyant forces in a fluid-saturated porous enclosure was studied experimentally. An electrochemical method was employed to establish the concentration gradients. The inside temperature profiles and heat and mass transfer coefficients on the vertical walls were determined experimentally. The effects of dimensionless parameter Ra, Le, N on flow, heat, and mass transfer are discussed in detail. © 1999 Scripta Technica, Heat Trans Asian Res, 28(4): 266–277, 1999 相似文献
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Yung-Kang Shen Chih-Yuan Chang Yu-Sheng Shen Sung-Chih Hsu Ming-Wei Wu 《International Communications in Heat and Mass Transfer》2008
Micro-injection molding is the most important technology in MEMS/NEMS industry for the necessary of scale, velocity and cost by the development of MEMS/NEMS industry and the innovation of MEMS/NEMS industry. It has the advantage of low cost, low interface and small volume in MEMS/NEMS industry. This paper emphasizes the analysis for microstructure of microlens arrays on micro-injection molding. The finite element simulation in a three-dimensional inertia-free, incompressible flow is presented. A control volume scheme with a fixed finite element mesh is employed to predict melt front advancement. The plastic material of microlens arrays is used for PMMA material. The results show the short shot on the filling stage of micro-injection molding. The results also indicate that the melt front first advance into the thickness direction of microlens arrays, and then it goes into the microstructure of microlens arrays. 相似文献
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This article explains the heat and mass transfer of electrically conducting Newtonian fluid in double-diffusive magnetoconvective flow. We have considered two infinite horizontal plates at a constant distance apart under the concentration-modulated boundary condition. A constant magnetic field is considered in vertically upward directions, which generates an induced magnetic field. We have used the weakly nonlinear analysis to obtain the heat and mass transfer rate using the Ginzburg–Landau equation. The software MATHEMATICA is used to determine the solution of the Ginzburg–Landau equation by inbuilt function. The effects of physical parameters that occurred in the study on the Nusselt number and Sherwood number have been examined graphically. Modulation has a negligible effect on the threshold value of the thermal Rayleigh number, that is, on stationary convection. Moreover, it was found that the Chandrasekhar number, magnetic-Prandtl number, amplitude of modulation, and frequency of modulation are proportional to the heat and mass transports. 相似文献
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Tsung-Lung Wu Keng-Liang Ou Hsin-Chung Cheng Chiung-Fang Huang Yung-Kang Shen Yuh-Chyun Chian Yi Lin Yu-Hao Chan Chien-Pang Li 《International Communications in Heat and Mass Transfer》2008
Precision injection molding is the most important technology in Bio-MEMS/NEMS industry for the necessary of scale, velocity and cost by the development of Bio-MEMS/NEMS industry and the innovation of Bio-MEMS/NEMS industry. It has the advantage of low cost, low interface and small volume in Bio-MEMS/NEMS industry. This paper emphasizes the analysis for three dimension biodegradable polymeric scaffold on precision injection molding. The finite element method in a three-dimensional inertia-free, incompressible flow is presented. A control volume scheme with a fixed finite element mesh is employed to predict flow front advancement. The plastic material of scaffold is used for PLA material. The results show that the short shot on the filling stage of precision injection molding. The results also indicate the processing window and optimal processing for three dimension biodegradable polymeric scaffold on precision injection molding. 相似文献
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China’s accelerator driven subcritical system (ADS) development has made significant progress during the past decade. With the successful construction and operation of the international prototype of ADS superconducting proton linac, the lead-based critical/subcritical zero-power facility VENUS-II and the comprehensive thermal-hydraulic and material test facilities for LBE (lead bismuth eutectic) coolant, China is playing a pivotal role in advanced steady-state operations toward the next step, the ADS project. The China initiative Accelerator Driven System (CiADS) is the next facility for China’s ADS program, aimed to bridge the gaps between the ADS experiment and the LBE cooled subcritical reactor. The total power of the CiADS will reach 10 MW. The CiADS engineering design was approved by Chinese government in 2018. Since then, the CiADS project has been fully transferred to the construction application stage. The subcritical reactor is an important part of the whole CiADS project. Currently, a pool-type LBE cooled fast reactor is chosen as the subcritical reactor of the CiADS. Physical and thermal experiments and software development for LBE coolant were conducted simultaneously to support the design and construction of the CiADS LBE-cooled subcritical reactor. Therefore, it is necessary to introduce the efforts made in China in the LBE-cooled fast reactor to provide certain supporting data and reference solutions for further design and development for ADS. Thus, the roadmap of China’s ADS, the development process of the CiADS, the important design of the current CiADS subcritical reactor, and the efforts to build the LBE-cooled fast reactor are presented. 相似文献
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Songzhe Chen Renling Wang Ping Zhang Laijun Wang Jingming Xu Yangchuan Ke 《International Journal of Hydrogen Energy》2013
In the thermochemical water-splitting iodine–sulfur process for hydrogen production, efficient concentration/separation of HI from HIx solution, a mixture of HI–H2O–I2, is very important. In this paper, an experimental study on concentrating HI in HIx using stacked electro-electrodialysis (EED) cells was carried out under the conditions of 1atm, 80 °C and the current density of 0.10 A/cm2. The performance of EED stacks including 1, 2 and 4 EED units was evaluated. The results showed that multi-unit EED cells could concentrate HI in catholyte much faster than single-unit cells. The apparent transport number (t+) of all the experiments were very close to 1, while the ratio of permeated quantities of water to H+ (β) changed in a relatively larger range of 1.98–2.89. Although the current efficiency will degrade faster when using a multi-unit stack than a single-unit cell at the late stage of EED process, at high iodine content multi-unit stack could maintain quite high current efficiency. 相似文献
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We consider one of the newest analytical methods, the Optimal Homotopy Asymptotic Method (OHAM), to solve nonlinear equations arising in heat transfer. Two specific applications are considered: cooling of a lumped system with variable specific heat and the temperature distribution equation in a thick rectangular fin radiation to free space. Results obtained by OHAM, which does not need small parameters are compared with numerical results and a very good agreement was found. This method provides us with a convenient way to control the convergence of approximation series and adjust convergence regions when necessary. The results reveal that the proposed method is explicit, effective and easy to use. 相似文献
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Optimal homotopy asymptotic method for heat transfer in hollow sphere with robin boundary conditions 下载免费PDF全文
In this article, we have investigated heat transfer from a hollow sphere using a powerful and relatively new semi‐analytic technique known as the optimal homotopy asymptotic method (OHAM). Robin boundary conditions are applied on both the inner and outer surfaces. The effects of Biot numbers, uniform heat generation, temperature‐ dependent thermal conductivity, and temperature parameters on the dimensionless temperature and heat transfer are investigated. The results of OHAM are compared with a numerical method and are found to be in good agreement. It is shown that the dimensionless temperature increases with an increase in Biot number at the inner surface and temperature and heat generation parameters, whereas it decreases with an increase in the Biot number at the outer surface and the dimensionless thermal conductivity and radial distance parameters. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res 43(2): 124‐133, 2014; Published online 20 June 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21067 相似文献
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基本Yong传递方式的科学确定,对复杂Yong传递过程或系统的研究极具价值。在分析评述现有研究成果的基础上,提出了作为基本Yong传递方式的充要条件。对多种复杂Yong传递系统的分解、分析,积累了丰富的Yong传递形式资料。据此提出四种基本Yong传递方式,作为应用列举了二个复杂Yong传递系统分解实例。 相似文献
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The object of the study is to clarify experimentally the variation of the vapor concentration of binary mixtures generated during nucleate boiling in a saturated pool under various boiling conditions. The generated vapor concentrations in the bulk vapor layer were measured for binary mixtures of water‐ethanol and ethanol‐acetone under various liquid concentrations, heat fluxes, and liquid layer heights from heated thin wires at atmospheric pressure. Two methods of measuring concentration, namely, the dew point method and the laser absorption method, were used. The dew point measurement utilized a copper heat transfer block installed in the center of the vapor layer in the boiling vessel. The commencement of condensation on the surface was observed directly via a microscope used for determining the dew point by controlling its temperature. A laser light having a wavelength of 3.39 µm was used for the laser light absorption method utilizing its absorptive property against ethanol vapor. The measurement of the concentrations of the bulk vapor was carried out for various superheats of heated wires, the depth of liquid mixture layer, and the liquid concentrations. They were almost independent of those parameters and were almost in equilibrium with bulk liquid conditions even under higher surface superheats and lower liquid heights. Also, the measured results using both methods were in close agreement. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 595–605, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10060 相似文献
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The problem of steady, laminar, coupled heat and mass transfer by MHD free convective boundary‐layer flow along a vertical flat plate with the combined effects of streamwise sinusoidal variations of both the surface temperature and the species concentration in the presence of Soret and Dufour effects is considered. A suitable set of dimensionless variables is used to transform the governing equations of the problem into a non‐similar form. The resulting non‐similar equations have the property that they reduce to various special cases previously considered in the literature. An adequate and efficient implicit, tri‐diagonal finite difference scheme is employed for the numerical solution of the obtained equations. Various comparisons with previously published work are performed and the results are found to be in excellent agreement. A representative set of numerical results for the velocity, temperature, and concentration profiles as well as the surface shear stress, rate of heat transfer, and the rate of mass transfer is presented graphically for various parametric conditions and is discussed. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21033 相似文献