Horizontal Upward Research Articles

Orientation effects on liquid-vapor phase change heat transfer on nanoporous membranes

Liquid-vapor phase change heat transfer on nanoporous membranes in facing horizontal upwards, downwards and vertically was investigated. Anodic aluminum oxide (AAO) membranes were as the nanoporous substrates. Water was supplied through nanoporous membranes by pressure difference. Heat transfer characteristics and temperature instability were analyzed and compared among three orientations. Results showed that negative slope and “special points” appeared on boiling curves. The interaction between liquid film thickness and heat transfer coefficient (HTC) was proposed and verified to be the main mechanism that leading to this phenomenon. Because the rapid replenishment of liquid and removal of heated liquid under gravity, horizontal downward surface always had the best heat transfer performance which exhibited maximal enhancement of HTC was 170% and 70% at heat flux of 39 W/cm2 over horizontal upward and vertical surfaces. Temperature instability in horizontal downward and vertical surfaces had the similar trend and became more pronounced at higher heat fluxes. In horizontal upward surface, temperature was stable at the heat flux range of 40– 55 W/cm2 and “thin film evaporation” was realized. In addition, the maximum heat flux was calculated by liquid transport limit and kinetic theory limit for evaporation and a comprehensive understanding was established.

Influence of milling toolpaths in machining of the turbine blade

PurposeThe purpose of this paper is to machine the pressure surface of the turbine blade made of A286 iron-based superalloy by using four directions of raster strategy, including horizontal upward, horizontal downward, vertical upward and vertical downward, to achieve appropriate surface roughness and to investigate the tool wear in each strategy.Design/methodology/approachIn this study, all cutting tests were performed by DAHLIH-MCV 1020 BA vertical 3-axis machining center with ball nose end mill. After milling by each strategy, according to the surface slope, the surface was divided into 27 meshes, and roughness of surface was studied and compared. Roughness measuring after machining was implemented by using portable Mahr ps1 roughness tester, and surface texture was photographed by CCD 100× optical zoom camera. Also, to measure tool flank wear in each strategy as an indication of tool life, the surface of workpiece was divided into four equal areas. The wear of the inserts was measured by ARCS vertical non-contact measuring system at the end of each area.FindingsThe results indicate that cutting directions and toolpath strategies have significant influence on tool wear and surface roughness in machining processes and that they can be taken into consideration individually as determinative parameters. In this case, the most uniform surface texture and the lowest surface roughness are obtained by using horizontal downward direction; in addition, abrasion is a dominant tool wear mechanism in all experiments, and tool wear in the horizontal downward is lower than other strategies.Practical implicationsMachining of turbine blades or other airfoil-shaped workpieces is quite common in manufacturing aerospace and aircraft products. The results of this research contribute to increasing quality of machined surface and tool life in machining of turbine blade.Originality/valueThis work proves the significance of milling strategies in machining of the turbine blade made of A286 superalloy and, consequently, exhibits the proper strategy in terms of surface roughness and tool life. Also, this work explains and elaborates the behavior of A286 superalloy in machining processes, which has not been studied much in recent research works.

Effect of heater orientation on pool boiling heat transfer from sintered copper microporous coating in saturated water

In this study, we investigate the heater orientation effects at inclination angles from 0° (horizontal upward) to 180° (horizontal downward) on pool boiling heat transfer of saturated water using a durable high-temperature thermally-conductive microporous coating (HTCMC) created by sintering copper powder of an average particle size of 67μm onto a 1cm×1cm plain copper surface with ∼300μm thickness. The HTCMC surface showed a critical heat flux (CHF) of ∼2MW/m2 and a maximum nucleate boiling heat transfer (NBHT) coefficient of ∼400kW/m2K, which are 2 and 8 times higher than those of a plain copper surface, respectively, at the upward horizontal inclination angle. The current experimental results showed that the CHF values of the HTCMC were maintained as ∼2MW/m2 at upward inclination angles from 0° to 90°, whereas the CHF values decreased as the inclination angle changed from 90o to 180o, at which point the values were ∼1.4MW/m2. The reduction at 180° is due to individual bubbles merging and forming larger bubbles by blockage from the surface. This increases the vapor residence time on the surface and prevents liquid access to the heated surface at downward inclination angles.However, it is noted that the CHF value of the HTCMC at 180° is ∼4.5 times higher than that of plain copper surface (0.3MW/m2 at 180°). HTCMC also shows a noticeably higher CHF value at 180° compared to nanocoating or other enhanced surfaces. This significant CHF enhancement is believed to be due to a large number of small feed jet bubbles created from porous structures, postponing the dryout caused by forming large bubbles on the heated surface.

Gas-Liquid Two Phase Flow Phenomenon in Near Horizontal Upward and Downward Inclined Pipe Orientations

Gas-Liquid Two Phase Flow Phenomenon in Near Horizontal Upward and Downward Inclined Pipe Orientations

The influence of cutter orientation and workpiece angle on machinability when high-speed milling Inconel 718 under finishing conditions

The paper details results from a comprehensive series of experiments on the effects of key operating variables; cutter orientation and workpiece tilt angle, on tool life/length cut, cutting force, workpiece surface roughness ( R a), subsurface microstructure/microhardness and residual stress, when high-speed milling under finishing conditions. In terms of length cut, the 8 mm diameter coated (TiAlCrN multi-layer) carbide ball nose end mills achieved tool life values approaching 200 m. Life results for the horizontal downwards orientation when cutting with a workpiece tilt angle of 45° were similar to those when operating with the workpiece mounted horizontally, however, cutting forces were significantly higher in the latter case. Evidence of tool chatter was also observed from cutting force signatures with the horizontal upwards mode. Mean compressive surface residual stresses up to ∼−850 MPa measured parallel to the feed direction were obtained when machining using worn tools with a 0° workpiece inclination, while tensile stresses were obtained when machining with horizontal downwards orientation.

Stomach Symptoms and Up-Down Metaphors and Gradients

Previous work demonstrated a relationship in an ulcer patient between stomach pain during psychotherapy sessions and preoccupation with up-down themes. The generality of this phenomenon was investigated by determining in normal males the relationship of number of stomach symptoms to various up-down parameters. A significant positive correlation was found between stomach symptoms and the shifting of horizontal upward. Stomach positive correlation was found between stomach symptoms and the shifting of horizontal upward. Stomach symptoms were also significantly positively correlated with an up-down physiology index (hand minus foot temperature). Finally, a borderline positive correlation was found between stomach symptoms and relative awareness of the upper as compared to lower sectors of one's body. The data suggest that the occurrence of stomach symptoms is linked to up-down sets or gradients at perceptual, physiological, and perhaps body image levels.