Liquid-fluid heat transfer at direct contact,accompanied by solidification. the cooling stage

Summary A mathematical model for the cooling process of a molten drop, falling freely in a fluid, is presented. This model is used to determine the duration of the cooling stage of an urea drop. The distribution of the temperature, as function of time and radius, is determined.     

Effect of the nonisothermicity of the wall on heat transfer in jet wetting

A method for solving a conjugate periodic convective-conductive problem for a "heat-transfer agent-wall" developed earlier system is used for calculation of the effect of the wall parameters on heat transfer under conditions of jet wetting.     

Kinetics and mechanism of solidification and heat transfer of epoxy composites

A model is constructed of the kinetics of epoxy resin solidification of isomethyl tetraphthalate anhydride in the presence of a ternary amine. Parameters of the kinetic equation are determined from tests and a computation is performed for an epoxy resin with solidifier of amine type. The method of space-time separation permitted estimation of the influence of rheokinetics on the flow and heat transfer of the partially polymerized fluid.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 3, pp. 387–394, September, 1990.     

Long-term wetting and corrosion characteristics of hot water treated aluminum and copper fin stocks

Experimental studies were conducted to investigate the long-term wetting and corrosion characteristics of hot water treated aluminum and copper fin stocks. This was done by subjecting them to wet/dry cycling consisting of alternately dipping the fin samples into distilled water for 5 min followed by air drying with a fan for 25 min. To simulate the fins of a heat exchanger, fin stocks were formed in a wavy shape using hand operated fin dies and a typical lubricant oil. The fin samples, including the formed and the unformed aluminum and copper stocks, were treated using hot water by immersing them in either 82 or 100 °C water for 20 min. The wettability and corrosion evaluations consisted of periodic measurements of the advancing/receding contact angles and weights of the fin samples. SEM photos were taken to show the appearance of the sample surfaces. Further, X-ray photoelectron spectroscope examinations were performed to analyze the atomic composition at the sample surfaces. The test results suggest that the hot water soak is an effective means to improve the surface wettability of both aluminum and copper surfaces. The soaking procedure was capable of producing wettable fin that was durable to wet/dry cycling. The soaking operation and follow-on wet/dry cycling treatment did not cause significant material loss by general corrosion.     

Finite-difference solution of the conjugate heat transfer,natural convection,and solidification problem

A mathematical model of the solidification of a binary melt under convection conditions with a two-phase zone taken into account is formulated on the basis of average transfer equations. Results of a numerical solution are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 2, pp. 286–293, August, 1984.     

Effect of copper addition and heat treatment on the depth dependence of the nanoindentation creep of aluminum at 300 K

Constant-load indentation creep tests were performed on pure aluminum and aluminum 4 wt% copper at 300 K to assess the influence of indentation depth, copper addition, and heat treatment upon the indentation creep rate. The stress dependence of the average indentation creep rate could be expressed for all the samples tested in terms of a mechanism of obstacle-limited dislocation glide. The calculated activation energy showed the same dependence upon indentation stress for all the conditions investigated.We therefore conclude that the indentation creep rate is limited by dislocation/dislocation interactions regardless of indentation depth, copper addition, or heat treatment. The presence of 4 wt% copper and heat treatment, however changes, the dislocation density, and hence the spacing of the dislocation–dislocation interactions.     

Nucleation and growth study of copper thin films on different substrates and wetting layers by metal-organic chemical vapour deposition

Chemical vapour deposition of copper thin films on different diffusion barrier/adhesion promoter layers have been studied. Copper thin films were grown in low pressure CVD reactor, using Cu(dpm)₂ as precursor and argon as carrier gas. Growth rates, film adhesion to the substrate, and surface morphology were studied in detail. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

The wetting of carbon by copper and copper alloys

The effects of alloying additions on the wetting of two types of carbon, HX30 graphite and vitreous carbon, have been investigated, with a view to developing a system for metal impregnation of carbon fibre assemblies. Pure copper is inert and non-wetting but two additions caused the copper to wet: Cr on both substrates and V on the vitreous carbon only. Many of the additions formed a carbide reaction layer at the interface, and in the two wetting systems this was a thin, continuous, coherent layer. The data have been analysed in terms of the chemical and physical properties of the system and it was found that the wetting behaviour of copper alloys on HX30 graphite and vitreous carbon could be explained in terms of the behaviour of the reaction product carbides of the alloying addition when these existed.     

Coupled problem of heat transfer,hydrodynamics, and solidification in a melt

A mathematical model is constructed which describes thermal and hydrodynamic phenomena accompanying the solidification process in a melt. The equations of hydrodynamics take into account viscoelasticity and compressibility of liquid metal. An example of calculations pertaining to solidification of an ingot is given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 6, pp. 1109–1118, December, 1981.     

The effect of varying chill surface roughness on interfacial heat transfer during casting solidification

Experiments to investigate interfacial heat transfer mechanisms during casting solidification were carried out by varying the surface roughness of a Cu chill used to bring about unidirectional solidification of an Al-4.5 wt.% Cu alloy. Little variation in interfacial heat transfer coefficient with varying chill surface roughness was found, confirming previously published results. Examination of the as-cast surface of the casting showed the presence of predendritic contact areas, and also that the casting surface roughness did not form as a replica of the chill surface, as has often been proposed. Rather, the casting surface roughness was consistently greater than that of the chill, but varied little in the experiments. A sum surface roughness parameter was devised to characterise the casting–chill interface that included the roughness of both surfaces. The value of this parameter was strongly influenced by the greater roughness of the casting surface, rather than the chill surface roughness, and therefore also varied little in the experiments. This lack of variation in the casting surface roughness and hence the sum surface roughness parameter showed how interfacial heat transfer should be more strongly influenced by the greater roughness of the casting surface than of the chill surface, and explains why the interfacial heat transfer coefficient was not strongly influenced by the chill surface roughness in these types of experiments. At the time the work was carried out the authors were in the Manchester Materials Science Centre, University of Manchester and UMIST, Manchester M1 7HS, UK.     

Influence of modification, solidification conditions and heat treatment on the microstructure and mechanical properties of A356 aluminum alloy

The effects of casting thickness, modification and heat treatment on the microstructure and mechanical properties of A356.2 alloy have been investigated. Experiments were conducted with unmodified, Sr-modified (0.02% Sr) and Sb-modified (0.2% Sb) on both sand cast test bars with various thicknesses (from 3 to 9 mm) and permanent mold cast test bars.The microstructural changes associated with these treatments have been studied by optical metallography, scanning electron microscopy (SEM) and image analysis.The tensile properties of all samples were determined and the relationship between cooling rate, modification and heat treatment has been investigated.The results show that modification has a beneficial effect on microstructure and improves the mechanical properties of the alloy. Modification has a major role in controlling the kinetics of the spheroidisation of silicon particles during heat treatment. Tensile properties improved more with heat treatment than with modification or cooling rate.Antimony is effective on mechanical properties at higher solidification rates, while Strontium is more effective at lower solidification rates.     

Interrelation between the parameters of solidification in a cylinder with axial and radial-axial heat transfer

A method is described of calculating the temperature field in the crystallization zone (twophase zone) which moves within a cylinder along the axis.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 1, pp. 106–109, July, 1970.     

Hydrodynamics,heat and mass transfer,and solidification in the formation of ingots and castings

A set of interrelated mathematical models is developed for processes of heat and mass transfer and solidification. Its scope is illustrated on specific examples of the calculation of cast-ingot formation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 3, pp. 450-458, September, 1989.     

多孔铝对流换热系数的反演分析

建立了多孔铝的一维瞬态对流换热模型,采用反演分析方法求得了多孔铝的体积对流换热系数.给出了多孔铝对流换热的无量纲准则关联式,并在较宽的孔结构范围内(孔隙率为60.0%～95.0%、孔径为2.5～6.0 mm)研究了孔结构对多孔铝换热系数的影响.结果表明:多孔铝的换热系数随着风速的增加而提高.在风速相同的条件下,换热系数随着孔径和孔隙率的减小而提高.在风机功率相同的条件下,换热系数随着孔隙率的增大而提高,在孔隙率约为85%时达到峰值.     

某冷凝器换热铜管腐蚀穿孔分析

针对某冷凝器中换热铜管发生腐蚀穿孔泄漏,进行宏观检查、化学成分分析、扫描电子显微镜检查以及腐蚀产物能谱分析,认为HSn70-l铜管在海水环境中发生脱锌选择性腐蚀是腐蚀导致铜管穿孔泄漏的主要原因,并给出防止HSn70-l铜管脱锌腐蚀的建议。     

一种新型高效传热铜管的冷凝传热性能实验研究

建立无润滑油实验台，以R22。R134a和R410A为工质。测试新型铜管Turbo-DWT和常规内螺纹铜管Turbo—A的冷凝传热性能，并进行比较。从实验数据可知。新管型Turbo-DWT的冷凝传热系数高于Turbo-A约42％，且压降低于Turbo-A约65％（R134a）。三种制冷荆相比，R22的传热系数最高，R410A的压降最小。Turbo-DWT是一种更高效的冷凝传热管，且适用于各种冷媒。     

内螺纹铜管齿形参数对传热性能的影响

利用R22单管传热试验台,对相同工况下不同结构参数的内螺纹强化管进行蒸发冷凝换热试验。通过对比分析试验数据,发现改变齿形参数对内螺纹管换热系数影响较大,且Tube-NEW换热性能优于其他管型。     

Determination of heat transfer coefficients during solidification of a casting in a jet crystallizer

The problem of determining heat transfer coefficients in thermal processes described by nonlinear initial boundary-value problems for heat conduction equations in a cylindrical coordinate system is considered subject to axial symmetry. An algorithm is suggested and program means are created for identifying heat transfer coefficients. A computational experiment on determining heat transfer coefficients for the AK12 alloy is carried out, and recommendations for selecting numerical calculation parameters have been developed.