Shiang-Wuu Perng

Effect of an oblique plate on the heat transfer enhancement of mixed convection over heated blocks in a horizontal channel

Abstract This study presents a numerical investigation on heat transfer enhancement of mixed convective flow in a horizontal block-heated channel. The heat transfer enhancement in this study has been accomplished by the installation of an oblique plate for internal flow modification induced by vortex shedding. The oblique angle of the plate is changed (30–90°) under Reynolds numbers (260–530) and Grashof numbers (0–3 200 000) for the purpose of investigating the heat transfer performance. The results show that the installation of an oblique plate in cross-flow above an upstream block can effectively enhance the heat transfer performance of mixed convection in the horizontal channel flow.

LES analysis of turbulent flow and heat transfer in motored engines with various SGS models

Abstract This paper presents the application of three different subgrid-scale (SGS) models in a large eddy simulation (LES) for investigating the turbulent flow field and wall heat transfer during the compression–expansion strokes in two types of engine configuration under realistic engine conditions. Predictions were compared with experimental measurements (including the local heat flux and swirl velocity), and with those calculated from the conventional K – e model. The results of the Van Driest wall damping model for LES were found to be in the best agreement with experimental data. The variations of velocity vector plots, isothermal profiles with crank angle were realized in the “Pancake” chamber engine. The variation of squish strength in the cylinder was also investigated by illustrating the friction velocity variations at different radial locations in the “Deep Bowl Piston” engine.

Turbulent flow and heat transfer enhancement of mixed convection over heated blocks in a channel

Purpose – To investigate the heat transfer enhancement performed by installing a rectangular plate turbulator for internal flow modification induced by vortex shedding.Design/methodology/approach – The large eddy simulation (LES) and SIMPLE‐C method coupled with preconditioned conjugate gradient methods have been applied to the turbulent flow field and heat transfer enhancement of mixed convection in a block‐heated channel.Findings – Provides information about heat transfer performance indicating that heat transfer performance can be affected by various width‐to‐height ratio of turbulator and Grasehof numbers with a constant Reynolds number. The results show that the installation of turbulator in cross‐flow above an upstream block can effectively enhance the heat transfer performance by suitable width‐to‐height ratio of turbulator and Grasehof numbers.Research limitations/implications – It is limited to two‐dimensional mean flow for the turbulent vortex‐shedding flow past a long square cylinder.Practical ...

Numerical investigation of anode thickness on the performance and heat/mass transport phenomenon for an anode-supported SOFC button cell

This study analyzes how anode thickness and working temperature affect heat/mass transport characteristics and cell performance of the anode-supported SOFC button cell by the finite-volume SIMPLE-C method coupled with preconditioned conjugate gradient methods. The numerical results of this work are compared with the experimental data and good agreement is observed. The simulation is carried out for various anode thicknesses (0.1, 0.5, and 1.0 mm) and working temperatures (873, 1073, and 1273K). The results showed that the cell performance reduces about 5.05% as the anode thickness is increased from 0.1 mm to 1.0 mm; however, the influence of anode thickness on the heat/mass transport phenomenon is slight because the geometric size of anode thickness is tiny for the whole SOFC. In addition, the cell performance increases about 50.54% as the working temperature is increased from 873 K to 1273 K. A higher working temperature enhances the fluid velocity and convection and consequently promotes the chemical reaction and obtains a better cell performance.

Squish effect of piston crown on the turbulent heat transfer in reciprocating engine

An axisymmetric two‐dimensional computer program employing the Large Eddy Simulation (LES) and SIMPLE‐C method coupled with preconditioned conjugate gradient methods is applied to the turbulent flows in the compression‐expansion strokes for various combustion chamber geometries under realistic engine conditions. The squish area percent of piston crown is changed (SQ = 0 percent for flat piston model, SQ = 46 percent for shallow bowl piston model and SQ = 76 percent for deep bowl piston model) under engine speeds (500∼1,500rpm) for the purpose of investigating the heat transfer performance. Comparison was made of present heat flux results and earlier experimental and numerical results. It is shown that the numerical method can predict the turbulence with reasonable accuracy. The results show that the configuration of piston crown for squish area percent can obviously enlarge the surface heat flux of wall boundaries in reciprocating engines.