Experimental and numerical study of heat transfer in hot machined workpiece using infrared radiation

One of the greatest problems found in machining is related to the cutting tool wear. A way for increasing the tool life points out to the development of materials more resistant to wear, such as PCBN inserts. However, the unit cost of these tools is considerable high, around 10 to 20 times compared to coated carbide insert, besides its better performance occurs in high speeds requiring modern machine tools. Another way, less studied is the workpiece heating in order to diminish the shear stress material and thus reduce the machining forces allowing an increase of tool life. For understanding the heat transfer influences by conduction in this machining process, a mathematical model was developed to allow a simplified numerical simulation, using the finite element method, in order to determine the temperature profiles inside the workpiece.

Two-Phase Frictional Pressure Drop and Flow Boiling Heat Transfer for R245fa in a 2.32-mm Tube

Experimental two-phase frictional pressure drop and flow boiling heat transfer results are presented for a horizontal 2.32-mm ID stainless-steel tube using R245fa as working fluid. The frictional pressure drop data was obtained under adiabatic and diabatic conditions. Experiments were performed for mass velocities ranging from 100 to 700 kg m−2 s−1 , heat flux from 0 to 55 kW m−2 , exit saturation temperatures of 31 and 41◦C, and vapor qualities from 0.10 to 0.99. Pressures drop gradients and heat transfer coefficients ranging from 1 to 70 kPa m−1 and from 1 to 7 kW m−2 K−1 were measured. It was found that the heat transfer coefficient is a strong function of the heat flux, mass velocity, and vapor quality. Five frictional pressure drop predictive methods were compared against the experimental database. The Cioncolini et al. (2009) method was found to work the best. Six flow boiling heat transfer predictive methods were also compared against the present database. Liu and Winterton (1991), Zhang et al. (2004), and Saitoh et al. (2007) were ranked as the best methods. They predicted the experimental flow boiling heat transfer data with an average error around 19%.

Exact and analytic-numerical solutions of lagging models of heat transfer in a semi-infinite medium

Different non-Fourier models of heat conduction have been considered in recent years, in a growing area of applications, to model microscale and ultrafast, transient, nonequilibrium responses in heat and mass transfer. In this work, using Fourier transforms, we obtain exact solutions for different lagging models of heat conduction in a semi-infinite domain, which allow the construction of analytic-numerical solutions with prescribed accuracy. Examples of numerical computations, comparing the properties of the models considered, are presented.

Az egyetemi technológiatranszfer szerepe az innovációs folyamatokban (The role of academic technology transfer in innovation processes)

A cikk ismerteti az egyetemi technológiatranszfer általános jellemzőit, majd egy, a világ minden táját érintő kitekintés segítségével röviden taglalja Magyarország és a Budapesti Corvinus Egyetem jelenlegi helyzetét az akadémiaiipari kapcsolatok fejlődésével és hatékonyságával kapcsolatban. Az eszmefuttatás a hazai és a nemzetközi szakirodalom eredményeit összefoglalva kísérletet tesz a technológiatranszfer definíciójának és folyamatának leírására, bemutatja az egyetemi technológiatranszfer jelentőségét az innovációs hálózatok szempontjából, majd felvázolja a következő Európai Uniós programozási időszak innovációval kapcsolatos legfontosabb hazai kihívásait.

Mennyit ér a zajterhelés csökkenése? Zajvédelmi intézkedések értékelése a haszonértékelések átvitelével (The value of silence. An application of benefit-transfer methodology for evaluating noise-control actions)

Mind ez ideig a gyakorlatban kevéssé aknázták ki azt a lehetőséget, hogy a természeti tőke pénzbeli értékelése számszerű, egzakt információt nyújthat a döntéshozóknak. A szerzők a zajvédelmi intézkedések példáján keresztül tekintik át a természeti tőkejavak közgazdasági értékelésében rejlő lehetőségeket. Ismertetik a költség-haszon elemzés környezeti javakkal bővített formájának előnyeit, majd az általában elhanyagolt, a nem piaci javak által nyújtott haszon közgazdasági értékelésére alkalmas eljárásokat, külön kitérve a zajterhelés területére. Nagy hangsúlyt helyeznek a haszonfelmérések átvitelének széles körben alkalmazható módszereire. Bemutatják az általuk gyakorlatban végzett kutatás során szerzett tapasztalatokat, különös tekintettel arra, hogy a haszonértékelések átvitele hogyan járulhat hozzá a természeti tőkejavakkal kapcsolatos döntések során a társadalmi haszon maximalizálásához. _____ The paper offers an overview of the economic valuation of transportation-induced noise and cost-benefit analysis of noise-control measures and actions. Although economic valuation can provide hard, monetized data for decision-makers, it is relatively underused in practice. The study focuses on benefit-transfer methodology, where values obtained in previous cases are used as the basis for current evaluation. A specific application of benefit transfer is presented by a recent pilot project in Hungary, whereby a tool was developed for LGOs, enabling them to make preliminary assessments of the benefits of potential noise-control measures and rank possible options. This can help to optimize the benefits to society using limited resources.

Metal transfer mapping for FCAW process by using near-infrared filming

In the Flux Cored Arc Welding (FCAW) process, the transfer of filler metal (metal transfer modes) to the base material to accomplish the weld bead determines the weld quality and therefore studies of such phenomena is demanded. Thus, in this work, the metal transfer through the FCAW process is investigated by filming the phenomena with the assist of near infrared visualization. During the literature survey, it was found that this technic has not been used so far for analyzing the FCAW process. It must be pointed out that the radiation emitted from the weld arc, fumes and particles (spattering) in this process represent a barrier for these studies based in the process visualization. The monitoring of metal transfer for FCAW process was carried out within the operational envelope of voltage and wire feed speed with the electrode E71T-1 (1.2 mm diameter) and Ar+25%CO2 as a shielding gas. A local developed near infrared filming with frame rate of 300 Hz was employed for metal transfer visualization in order to contribute to a better understanding of this process and evaluating characteristics of metal transfer, unlike previous studies, which used shadowgraph technique. It can clearly be seen how the droplet is created and transferred in this process and also identify the different modes of metal transfer by changing the parameters of voltage and wire feed speed in metal transfer maps. The final result of this study is the metal transfer mode maps, which establish suitable conditions and provide the basis for developing arc control strategies for the FCAW process.

Air-sea transfer of gas phase controlled compounds

Gases in the atmosphere/ocean have solubility that spans several orders of magnitude. Resistance in the molecular sublayer on the waterside limits the air-sea exchange of sparingly soluble gases such as SF6 and CO2. In contrast, both aerodynamic and molecular diffusive resistances on the airside limit the exchange of highly soluble gases (as well as heat). Here we present direct measurements of air-sea methanol and acetone transfer from two open cruises: the Atlantic Meridional Transect in 2012 and the High Wind Gas Exchange Study in 2013. The transfer of the highly soluble methanol is essentially completely airside controlled, while the less soluble acetone is subject to both airside and waterside resistances. Both compounds were measured concurrently using a proton-transfer-reaction mass spectrometer, with their fluxes quantified by the eddy covariance method. Up to a wind speed of 15 m s-1, observed air-sea transfer velocities of these two gases are largely consistent with the expected near linear wind speed dependence. Measured acetone transfer velocity is ~30% lower than that of methanol, which is primarily due to the lower solubility of acetone. From this difference we estimate the "zero bubble" waterside transfer velocity, which agrees fairly well with interfacial gas transfer velocities predicted by the COARE model. At wind speeds above 15 m s-1, the transfer velocities of both compounds are lower than expected in the mean. Air-sea transfer of sensible heat (also airside controlled) also appears to be reduced at wind speeds over 20 m s-1. During these conditions, large waves and abundant whitecaps generate large amounts of sea spray, which is predicted to alter heat transfer and could also affect the air-sea exchange of soluble trace gases. We make an order of magnitude estimate for the impacts of sea spray on air-sea methanol transfer.

Development of two charge transfer complex spectrophotometric methods for determination of tofisopam in tablet dosage form

Purpose: To develop a simple, fast and sensitive spectrophotometric method for the determination of tofisopam in tablet dosage form. Methods: Tofisopam as n-electron donor was reacted with two π-acceptors, namely, chloranilic acid (ChA), and 7,7,8,8 tetracyanoquinodimethane (TCNQ) to form charge transfer complexes. The complexes were evaluated spectrophotometrically at 520 and 824 nm for ChA and TCNQ, respectively. The optimum conditions for the reaction were determined and optimized. The developed method was compared with Japanese Pharmacopeia method. Results: The calibration curve was linear in the ranges 25 – 125 and 30 – 150 μg/mL for ChA and TCNQ, respectively. The lower limit of detection was 8.0 and 10.0 μg/mL for ChA and TCNQ, respectively while the slope and intercept of the calibration curves were 0.0025 and 0.011 and 0.0115 and -0.237, for ChA and TCNQ, respectively. Conclusion: The developed methods for tofisopam have good accuracy and precision, and comparable to a standard pharmacopeial method. The methods can be applied for routine analysis and in quality control.

Micropolar flow in a porous channel with high mass transfer

Two dimensional flow of a micropolar fluid in a porous channel is investigated. The flow is driven by suction or injection at the channel walls, and the micropolar model due to Eringen is used to describe the working fluid. An extension of Berman's similarity transform is used to reduce the governing equations to a set of non-linear coupled ordinary differential equations. The latter are solved for large mass transfer via a perturbation analysis where the inverse of the cross-flow Reynolds number is used as the perturbing parameter. Complementary numerical solutions for strong injection are also obtained using a quasilinearisation scheme, and good agreement is observed between the solutions obtained from the perturbation analysis and the computations.