Flow Path Surface Research Articles

Validation of Estimation of Flow-Path Structure and Prediction of Temperature Change Using 3D Printed Fracture Network

Reinjection of wastewater from geothermal power plants has been standard in geothermal development. Since reinjected water, however, may cool production areas, assessment of injected-water flow within subsurface structures is required. Suzuki et al. (2022) successfully validated an estimation of flow-path surface areas with long-term temperature data by thermal breakthrough experiments using a fracture structure created by a 3D printer. In this study, we improved their experiment to fit with the assumption of the mathematical model in the estimation method. As a result, we could improve the experimental setup and verified the estimation and prediction of future temperature change based on short-term temperature data.

Estimation of particle impact based erosion using a coupled direct particle — Compressible gas computational fluid dynamics model

A comprehensive two-phase compressible gas-solid particle computational fluid dynamics-based modeling method has been developed and applied to study the erosion and fouling along flow path surfaces due to particle impact. Extending upon methods to predict particle interaction phenomena which incorporate rolling, twisting, sliding, and adhesion forces to capture conditions that frequently occur as particle laden flow passes over a flow path surface, the simulation methods have been specifically designed for high particle concentrations and large particle sizes. In the developed technique, individual particles are directly discretized in the computational mesh, and the particles move through the fluid, and interact with the flow, flow path boundaries, and other particles. With particle motion calculated from the direct two-phase flow simulations, the distribution and intensity of the mass loss or erosion conditions along a flow path surface resulting from particle impact is predicted. The developed method was applied to study the erosion of an aluminum wall due to impacting sand particles of different sizes, impact velocities, and counts. A more fluid-like particle motion and distribution upon impact were found as the particle size decreased. The method was also implemented to examine the erosion that develops for three common flow configurations which force particle-flow path surface interactions: a diverging/converging flow path, a bypass flow path, and a baffle configuration. These applications demonstrate the utility of the model to explore and better understand the relationships between the geometry, the flow, the particles, and the adhesion and erosion that develop as particle laden flow moves over the flow path surfaces.

Numerical Analysis of Flow and Thermal Performance of Liquid-Cooling Microchannel Heat Sinks with Bifurcation

Single-phase liquid-cooling microchannels have received great attention to remove the gradually increased heat loads of heat sinks. Proper changes of the flow path and/or heat transfer surface can result in much better thermal performance of microchannel heat sinks. In this study, a kind of rectangular straight microchannel heat sink with bifurcation flow arrangement has been designed, and the corresponding laminar flow and heat transfer have been investigated numerically. Four different configurations are considered. The effects of the bifurcation ratio (the initial channel number over the bifurcating channel number) and length ratio (the channel length before bifurcation over the bifurcation channel length) on laminar heat transfer, pressure drop, and thermal resistance are considered and compared with those of the traditional straight microchannel heat sink without bifurcation flow. The overall thermal resistances subjected to inlet Reynolds number and pumping power are compared for the five microchannel heat sinks. Results show that the thermal performance of the microchannel heat sink with bifurcation flow is better than that of the corresponding straight microchannel heat sink. The heat sinks with larger bifurcation ratio and length ratio provide much better thermal performance. It is suggested to employ bifurcation flow path in the liquid-cooling microchannel heat sinks to improve the overall thermal performance by proper design of the bifurcation position and number of channels.

Practical analysis of degradation of rotating machines

A study on how degradation develops and affects the performance of the process rotating machine is presented. Main degradation reasons are identified as increased clearances, component geometry changes and flow path surface quality modifications. Parameters that indicate levels of degradation are outlined, thus providing guidance for machine specification, condition monitoring practice and renovation methods. Case study and experimental data are provided that supports the theoretical conclusion.

Heat Transfer Enhancement in Honeycomb Elements

In recent years, honeycomb elements made of ceramics have often been used for such purposes as heat exchangers, catalysts and adsorbents. Because such honeycomb elements have a smooth flow path surface, laminar flow prevails at or near the design point (Re=1000-4000), thereby leading to frequent cases of insufficient heat transfer coefficient. However, there have been quite few studies on the heat transfer enhancement in honeycomb elements. In the present research, experiments were conducted to investigate the effects of spacing and lateral shifting of elements on heat transfer coefficient using honeycomb elements of ceramics 6.07 mm width of opening and 1.13 mm in wall thickness, and enhancements in heat transfer by these effects were clarified. It was found that lateral shifting of elements was more effective in making the flow more turbulent to enhance the heat transfer than spacing of elements.