Rethinking Basic Assumptions for Modeling Parasitic Capacitance in Inductors

<b>This paper rethinks the basic assumptions often used in analytically modeling parasitic capacitance in inductors. These assumptions are classified in two commonly-used physics-based analysis methods: the lumped capacitor network method and the energy conservation method. The lumped-capacitor network method is not the proper solution for calculating the equivalent parasitic capacitance in inductors at the first resonant frequency, but rather represents the equivalent parasitic capacitance above the last resonant frequency. The energy-conservation based method is shown to be more accurate and a reasonable solution to model the equivalent parasitic capacitance at the first resonant frequency. Multiple case studies of inductors are used for verifying the theory. </b>

Rethinking Basic Assumptions for Modeling Parasitic Capacitance in Inductors

<b>This paper rethinks the basic assumptions often used in analytically modeling parasitic capacitance in inductors. These assumptions are classified in two commonly-used physics-based analysis methods: the lumped capacitor network method and the energy conservation method. The lumped-capacitor network method is not the proper solution for calculating the equivalent parasitic capacitance in inductors at the first resonant frequency, but rather represents the equivalent parasitic capacitance above the last resonant frequency. The energy-conservation based method is shown to be more accurate and a reasonable solution to model the equivalent parasitic capacitance at the first resonant frequency. Multiple case studies of inductors are used for verifying the theory. </b>

Energy conservation and heat transfer enhancement for mixed convection on the vertical galvanizing furnace

The alloying temperature is an important parameter that affects the properties of galvanized products. The objective of this study is to explore the mechanism of conjugate mixed convection in the vertical galvanizing furnace and propose a novel energy conservation method to improve the soaking zone temperature based on the flow pattern and heat transfer characteristics. Herein, the present study applied the k-? two-equation turbulence model to enclose the Navier-Stokes fluid dynamic and energy conservation equations, and the temperature distributions of the steel plate and air-flow field in the furnace were obtained for six Richardson numbers between 1.91 ? 105 and 6.30 ? 105. In the industrial practice, the side baffles were installed at the lateral opening of the cooling tower to alter the height of vertical flow passage, which affected the Richardson number. The results indicate that the Richardson number of 2.4 ? 105 generated the highest heat absorption and maximal temperature in the steel plate due to the balance between natural and forced convection. Furthermore, the results of the on-line experiments validated the simulation research. The method enhanced the steel plate temperature in the soaking zone without increasing the heat power, thereby characterizing it as energy conservation technology.

Energy Conservation Method Combining Anti spray Rail and Wedge Flap for High speed Displacement Hulls

The hydrodynamic mechanism and parametric influences of the wedge flap and the anti-spray rail in combination is investigates. A methodology with specific guidelines for incorporating these appendages with significant drag reduction is provided. Small crafts designs frequently require interventional changes to realise the desired guaranteed speed with their installed engine power. The appendages namely, the wedge, flap and anti-spray rails are used as retrofit measures or adapted in new hull forms, in isolation or in combination, to improve the drag and bring down the power requirement. A judicious combination of different appendages can result in significantly reduced drag and therefore power saving. The methodology combines the results of numerical and experimental investigations. The systematic study identifies the parameters for control namely, wedge flap size in terms of the chord length, its orientation vide the angle of the wedge flap, and the anti-spray rail location with respect to the water surface. The choice of the size of the wedge flap is a constrained problem since excessive wedge flap can cause problems related to length and hydrodynamic loading. This study establishes a solution by combination of a minimum integrated wedge flap with properly located anti-spray rail to reduce the drag. The study shows favourable influences due to local pressure and numerical results using a RANSE solver show good comparison with experimental test results. The methodology is a new approach towards drag reduction in new designs as well as drag control by retrofit.

Effects of axial impact load on the dynamics of an oilwell drillstring

This article studies the dynamics of oilwell drillstring under large and small axial impact loads. For the case of large impact load, the drillstring is regarded as a continuous bar under the impact load of a falling mass, and the energy conservation method is implemented. A sensitivity analysis is conducted to investigate the effect of cross-sectional area of the drill string on the impact stress. Results show that the design of drillstring with different cross-sectional areas is not a suitable method. In order to understand the effect of high-frequency small axial impact (applied from percussion tools or downhole generators) on the drillstring vibration, a mechanical model in which the drillstring is regarded as a 2-degree-of-freedom system under a harmonic force is developed. Sensitivity analysis on the effects of impact generator placement and impact frequency on drillstring dynamics are conducted. Results show that the impact generator should be installed near the drill bit and that high frequency is recommended to be used.