다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

http://repositorium.sdum.uminho.pt/bitstream/1822/48763/1/1-s2.0-S037026931200857X-main.pdf

Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC

https://digital.csic.es/bitstream/10261/108964/1/experiment%20at%20the%20LHC.pdf

Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.

The ATLAS Experiment at the CERN Large Hadron Collider

National Institute of Standards and Technology における超伝導研究及び生活

Due to tube enhancements being used to improve process efficiencies, heat exchangers are starting to operate in the transitional flow regime. Unfortunately, heat transfer and pressure drop performances in this flow regime is un-explored for many heat transfer geometries. In this preliminary study, experiments were conducted on the annular passage of a horizontal concentric counter-flow tube-in-tube heat exchanger operated with water for non-fully developed flow associated with a standard inlet geometry type. The annular diameter ratio, defined as the inner wall diameter over the outer wall diameter, was 0.386. An approximate uniform wall temperature on the inner annular wall surface was considered for varying annular mass flow rates that covered all flow regimes. Both heated and cooled cases of the annulus were examined. It was found that the heat transfer and pressure drop characteristics, based on the hydraulic diameter are different from those in circular tubes. The transition from laminar to turbulent flow, based on the Nusselt number, appeared to occur earlier than based on the friction factor. Nusselt numbers for heated annulus case, based on Reynolds number, were high than that for the cooled case. Conversely, the friction factors were higher for the cooled annulus case than for the heated case, while the adiabatic friction factors were the lowest. INTRODUCTION Heat exchanger design guidelines normally advise that designs should be done either for the laminar or for the turbulent flow regimes. However, design constraints and energy requirements have often lead to heat exchangers operating outside their design parameters. These parameters often involve the heat exchanger operating in the transitional flow regime [1]. Unfortunately, heat transfer and pressure drop performances in the transitional flow regime is un-explored for many heat transfer applications including that of annular passages of tube-in-tube heat exchangers, one of the most common heat exchanger types. The ratio of the inner tube’s outer diameter to the outer tube’s inner diameter, known as annular diameter ratio, has been reported to have an influence on both heat transfer and friction factor characteristics in such a heat exchanger type [2]. NOMENCLATURE As [m] Surface area cp [J/kg.K] Specific heat at constant pressure D [m] Diameter f [-] Friction factor h [W/mK] Convection heat transfer coefficient k [W/m.K] Thermal conductivity Ldp [m] Pressure drop length Lhx [m] Heat exchange length m [kg/s] Mass flow rate n [-] Number of thermocouples Nu [-] Nusselt number Re [-] Reynolds number p  [kPa] Pressure drop Q [W] Heat transfer rate T [°C] Temperature V [m/s] Average velocity

Heat transfer and pressure drop characteristics of a horizontal annular passage in the transitional flow regime

Numerical Study of Heat Transfer Characteristics for Different Solar Flux Distributions on Linear Fresnel Collector Absorber Tubes in Laminar Flow

Few studies are available in the literature on diabatic liquidvapour flows in inclined tubes. The present paper is dedicated to an experimental study of convective condensation of R134a in an 8.38 mm inner diameter smooth tube in inclined orientations. Flow patterns, heat transfer coefficients and pressure drops are presented as function of the inclination angle for different mass fluxes and vapour qualities. Tilting influences the flow patterns and thus the heat transfer coefficients for low mass fluxes and low vapour qualities. An optimum inclination angle that leads to the highest heat transfer coefficient can be found for downward flow. The study of the pressure drops in inclined orientations requires the distinction between the frictional and the gravitational pressure drops. However, a void fraction sensor is necessary to measure the gravitational pressure drops.

Experimental study of convective condensation of R134a in an inclined tube

Experimental and analytical work was performed and visual observations made to investigate the flow regimes during condensation of the refrigerants R-22, R-407C and R-134a in horizontal smooth, helical micro-fin, and herringbone micro-fin tubes at an average saturation temperature of 40°C, with mass fluxes ranging from 300 to 800 kg m -2 s -1 . The flow regimes observed were mainly annular flow and intermittent flow. At low mass fluxes and low average vapour qualities, however, stratified wavy flow was observed. The experimental results show that the transition from annular to intermittent flow regimes occurred at average mass fraction values of 26%, 29% and 48% for the herringbone micro-fin, helical micro-fin, and smooth tubes, respectively. The Thome flow regime transition criterion for annular to intermittent flow, together with the Froude rate and Martinelli parameter, were used to characterize the prevailing flow regime. The combined analyses made it possible to adapt the condensation flow pattern map for helical micro-fin tubes in such a way that it can generate a valid and accurate flow regime map for condensation in herringbone micro-fin tubes. The new transition criterion effectively predicts the delay in the transition from annular to intermittent flow for all three refrigerants condensing in the herringbone micro-fin tube. This new flow regime map has never before been produced for enhanced tubes, and represents an important advance in the field of practical heat-exchanger design.

A flow regime map for refrigerant condensation in herringbone micro-fin tubes

Correlation models for the prediction of condensation heat transfer performance of inclined smooth tubes are very scarce in literature. Most of the available models are limited to horizontal and vertical tube orientations. This paper presents a correlation model for the prediction of heat transfer coefficient during the convective condensation of R134a in a smooth inclined tube-intube condensing heat exchanger subject to diabatic conditions. The authors, in previous investigations presented the experimental data which have been used for the development of the proposed model. In this particular study, the test matrix comprises 260 data test points for inclination angles varying between -90 degrees (downward flow) and + 90 degrees (upward flow), for mass fluxes between 100 kg/m 2 s and 400 kg/m 2 s, mean vapour qualities between 0.1 and 0.9 at saturation temperature of 40°C. In the developed model, the effects of the independent variables such as mean vapour quality, mass flux and inclination are well captured. The proposed empirical model is in good agreement with the experimental data and performed better than the other models used for comparison. INTRODUCTION Condensation of refrigerant inside inclined smooth tubes has in recent times received attention due to its application in Aand Vframe heat exchangers. Such heat exchange equipment types have been used especially in remote areas where water is scarce and where air-cooled systems are the best option to sustain cooling of condensers in power plants and refrigeration plants. There are numerous correlations in literature which may be employed to predict the heat transfer coefficient in horizontal and vertical tube orientations. This is due to the fact that most of the available heat exchange equipment used in the refrigeration and air conditioning systems and other industries are in these orientations. Some of the recent correlation models include those for horizontal tubes [1 – 2], for vertical tubes [3 – 4] and for inclined tubes [5]. For a horizontal tube orientation, Cavallini et al. [1] proposed a heat transfer model for smooth tubes of inner diameters greater than 3.0 mm. The model was developed for different types of fluids and thermal conditions. When compared with other correlations, it gives relatively good results. Jung et al. [2], in their study on the condensation heat transfer coefficient of pure refrigerants in horizontal smooth tubes with an outer diameter of 9.52 mm and a length of 1.0 m considered the effects of vapour quality and mass flux for various fluids. The investigation was subjected to the following operating conditions: mass fluxes of 100 kg/m 2 s, 200 kg/m 2 s and 300 kg/m 2 s, vapour qualities between 0.1 and 0.9 and heat fluxes of 7.3 to 7.7 kW/m 2 at saturation temperature of 40°C. Based on their data they developed a heat transfer coefficient correlation. On vertical flows, Dalkilic et al. [3, 4] experimentally investigated the heat transfer coefficient during the condensation of R134a in downward flow for both laminar and annular flow pattern cases in smooth tubes. They considered mass fluxes ranging between 29 kg/m 2 s and 515 kg/m 2 s, saturation temperatures of 40°C to 50°C, heat fluxes between

Josua P. Meyer

Papers

Heat transfer and pressure drop characteristics of a horizontal annular passage in the transitional flow regime

Numerical Study of Heat Transfer Characteristics for Different Solar Flux Distributions on Linear Fresnel Collector Absorber Tubes in Laminar Flow

Experimental study of convective condensation of R134a in an inclined tube

A flow regime map for refrigerant condensation in herringbone micro-fin tubes

A condensation heat transfer correlation for inclined smooth tubes