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Thermal behaviors and flow profiles in a square channel fitted with X–V modified ribs: A numerical analysis
(2023-09-01)
Boonloi, Amnart
;
Jedsadaratanachai, Withada
A novel design of “X–V rib” turbulators is proposed to improve fluid blending and to perturb thermal boundary layer (TBL) in a heat exchanger (HX) duct. Better fluid blending and more highly disturbed TBL are the two important factors for the improvement of HX performance. Effects of X–V rib geometrical parameters including rib height ratios (b/H = 0.05–0.20), rib arrangements (V-tip pointing upstream called “V-Upstream (VU)” and V-tip pointing downstream called “V-Downstream (VD)”) and rib types (I, II and III) on air stream and thermal mechanisms are numerically investigated in a 3D model. The numerical model is solved with the finite volume method (a commercial code) and a commercial program. Laminar air flow (inlet conditions with Re = 100–2000) is a selected range of the present investigation. Firstly, the created numerical model for the ribbed duct is validated with two significant topics: 1. Plain duct validation and 2. Optimum grid elements (grid independence). The validated results show that the ribbed-duct model has great reliability to simulate air stream and thermal characteristics. According to the numerical results, the disturbed TBL is obviously found in all rib types. Moreover, it is observed that the core flow disturbance occurs and improves fluid blending. The outcomes from the present investigation point out that the knowledge about flow structure and thermal mechanism are important guidelines for the development of vortex turbulators and HX improvement. For the thermal assessments, it is found that the best Nusselt number ratio (Nu/Nu<inf>0</inf>) is 11.80 for the type III X–V rib with b/H = 0.20 in the VD-direction. Additionally, the maximum thermal enhancement factor within our investigated range is 3.48 at Re = 2000, b/H = 0.20, type II X–V rib in the VU-direction.
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Dependence Of Tunnel Deformation Due To Adjacent Pile Under Loading On Tunnel Geometry
(2019-01-01)
Lueprasert, Prateep
;
Jongpradist, Pornkasem
;
Ruangvirrojanakul, Kodchamon
;
Suwansawat, Suchatvee
With rapid urbanization, large number of tunnels with various dimensions have been constructed for transportation and utility systems in many big cities. At the same time, the constructions of infrastructures using a pile foundation system are also necessary in urban area. With limited space, the existing tunnels can be inevitably impacted by the newly constructed pile-supported structures. With various design criteria of tunnel lining, the size and thickness are varied from project to project. With an adjacent pile under loading, different degrees of impact on these tunnels are expected. This study numerically investigates the effect of tunnel diameter and lining thickness on tunnel deformation due to adjacent pile under loading. The MRTA and WMA tunnels in Bangkok subsoil are chosen as the reference cases for investigation. From a series of parametric study, a relationship between the tunnel deformation and dimensionless parameter, which include the size and thickness of lining, can be successfully established.
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Numerical electromagnetic analysis with the PEEC method
(2015-01-01)
Yutthagowith, Peerawut
The conventional full-wave formulation of the partial element equivalent circuit (PEEC) method was derived from the mixed-potential integral equation (MPIE) for the free space by A. E. Ruehli in 1974. The final results are interpreted Maxwell’s equations to a circuit domain by inductance, capacitance, and resistance extraction including retardation in theory. In that time, the retardation is neglected because the minimum wavelength corresponding to the considered maximum frequency is longer than dimensions of an interested domain. His development is based on the concept of inductance and capacitance extraction, which was firstly introduced by Rosa in 1908, and further developed by Grover in 1946 and Hoer and Love in 1965. Despite the fact that the PEEC method has an exact field theoretical basis, it was not primarily developed for the computation of electromagnetic fields. Instead, the circuit designer has a tool at hand to analyze the parasitic effects on connecting structures of circuits without leaving the familiar area of a network theory. This method was considerably developed further in the 1990s where retardation, external field excitation, and the treatment of a dielectric material were investigated.
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Development of tunneling influence zones for adjacent pile foundations by numerical analyses
(2013-02-01)
Jongpradist, Pornkasem
;
Kaewsri, Theerapong
;
Sawatparnich, Attasit
;
Suwansawat, Suchatvee
;
Youwai, Sompote
In this study, three-dimensional elasto-plastic numerical analyses are conducted to investigate the influences of tunnel excavation on existing loaded piles. The effects of parameters on pile responses to be used as criteria for suggesting the influence zones can be captured from the analysis method. A large number of analyses are then carried out to generate the artificial data of pile responses from tunneling for establishing the influence zones. Deep and shallow tunneling are separately considered with their influence zones are suggested from the normalized pile settlement and the induced pile bending moment, respectively. The two zones are then combined. Based on the ground condition, geometries of the pile and the tunnel, tunnel construction method, and evaluated criteria considered in this study, the unique significant zones of influence for various conditions can be identified. © 2012 Elsevier Ltd.

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