Analytical model for heat absorption: Lessons learned from a one dimensional model

Analytical water quality model for biochemical oxygen demand simulation in River Gomti of Ganga Basin, India

A total beam compression of 5 and 10 corresponding to the asymmetry angles of 9° and 12° is achieved with V‐5 and V‐10 monochromators, respectively, in standard single crystal pure germanium (220) X‐ray beam compressing (V‐shaped) monochromators for CuKα1 radiation. A higher 1D compression of X‐ray beam is possible using larger angles of asymmetry, however it is achieved at the expense of the total intensity, which is decreased due to the refraction effect. To increase the monochromator intensity, several ways are considered both theoretically and experimentally. Linearly graded germanium rich GexSi(1−x) single crystal was used to prepare a V‐21 single crystal monochromator with 15° asymmetry angles (compression factor of 21). Its temperature gradient version is discussed for CuKα1 radiation. X‐ray diffraction measurements on the graded GeSi monochromator showed more than 3‐times higher intensity at the output compared with that of a pure Ge monochromator.

Supplemental shielding of BMIT SOE-1 at the Canadian Light Source

Permanent magnet (PM) machines with concentrated windings are increasingly used in industry because of their cost-effectiveness and low production time. Eddy current losses in the rotor of these machines are significant due to a large content of space harmonics in air gap MMF. Analytical and finite element (FE) models have been formulated to predict such losses. This paper presents experimental validation for an analytical and a FE model, in which an openslot and a semi-closed-slot fractional-slot PM machine with 27 slots and 18 poles are modeled. The experiments consist of static tests for both the analytical model and the FE model, and rotary tests only for the FE model. The results show the models can to some extent predict the eddy current losses in the rotor but further improvements such as a three dimensional model may help reduce the deviations between models and experiments.

Transient hygro-thermo-mechanical stresses analysis in multi-layers bonded structure with coupled bidirectional model

It is quite common to employ thin metallic films for the determination of heat transfer rates at a fluid -solid interface. Depending on the duration of the event and gage design, it may be important to account for multi -dimensional heat conduction within the substrate of the thin film. The objective of this work is to assess the effects of two -dimensional heat conduction on the deduced radiative heat fluxes using a conjugate -gradient based inverse algorithm. For comparison, a previously developed one -dimensional inverse technique is also used. The high heat fluxes are produced by an electrothermal -chemical plasma jet. The plasma, initiated within a 3.2 mm diameter and 26 mm long polyethylene capillary by exploding a 3.6 mg thin copper wire, emerges into an open -air atmosphere as a high temperature, high -pressure, underexpanded sup ersonic jet. The jet impinges over a stagnation plate equipped with thin -film sputtered platinum heat -flux gages, whose temperature history serves as an input to the heat -flux estimation algorithm. Four different charging voltage levels are investigated, r anging from 2.5 to 7.5kV. While both algorithms capture the temporal variations of the radiative heat fluxes, two -dimensional heat conduction model reveals the discrepancies between the two techniques as well as the range of applicability of the one -dimens ional model.

The thermal deformation appearing in indium antimonide infrared focal plane arrays (InSb IRFPAs) subjected to thermal shock tests, will easily incur the fracture of InSb chip, this phenomenon restricts the final yield of InSb IRFPAs. In light of the proposed equivalent method, the three dimensional structural modeling of InSb IRFPAs is developed, and the simulated strain distributions are consistent with the buckling pattern, the shallow groove and the local flatness, appearing on the top surface of InSb IRFPAs at the corresponding regions. After comparing the deformation profiles at different regions, we deduce that the top surface flatness of InSb IRFPAs will be improved with frustum pyramid indium bump arrays, and this deduction is verified by the subsequent simulation results. That is, when the top surface area of indium bump is smaller than its bottom surface area, in this paper, the diameter of indium bump bottom surface is set with 24 μm, the simulated Z-components of strain is uniformly covering the whole top surface of InSb IRFPAs, and the deformation amplitude is decreased slowly with the decreasing top surface area of indium frustum pyramid arrays. These findings are beneficial to further improve the flatness of InSb IRFPAs, correspondingly, to lengthen its temperature cycling life.

An analytical predictive model for residual stress in laser-assisted milling considering material recrystallization caused by laser preheating is proposed. The laser preheating temperature field is predicted by treating the laser beam as a heat source on top surface following Gaussian distribution. Heat convection between top surface and the environment is factored into account. Isothermal boundary conditions are assumed for the area of interest with conduction within the material. Next, the milling configuration is treated as orthogonal cutting at each instance. All process parameters including cutting depth, cutting speed, and tool geometry are therefore transferred. The recrystallization effect and thus the grain growth are considered through calibrated models describing the dependency of strain rate, strain, and temperature on dynamic recrystallization process for specific alloys using exponent functions. The residual stress is then predicted through the calculation of elastic stress distribution in loading process, actual stress with kinematic hardening, and the stress change during relaxation. The proposed model is validated through experimental measurements on the laser-assisted milling of Si3N4 and Ti-6Al-4V. The predictive model matches the trends of experimental measurements with agreement to an average error less than 30% in all cases. The proposed analytical model is valuable for providing a fast, credible, and physics-based method for the prediction of residual stress in laser-assisted milling of various materials.

In this paper, a new two dimensional (2D) analytical modeling and simulation for a surrounding gate tunnel field effect transistor (TFET) is proposed. The Parabolic approximation technique is used to solve the 2-D Poisson equation with suitable boundary conditions and analytical expressions for surface potential and electric field are derived. This electric field distribution is further used to calculate the tunneling generation rate and thus we numerically extract the tunneling current. The results show a significant improvement in on-current characteristics while short channel effects are greatly reduced. Effectiveness of the proposed model has been confirmed by comparing the analytical results with the TCAD simulation results.

Sound propagation in pipes and ducts with flow, like ventilation ducts and exhaust pipes, is influenced by flow separation and vortex production at sharp edges along the ducts, such as at bends and area expansions. Shear layers form at the separation points, and such layers are unstable to low frequency acoustic disturbances. An analytical model, aiming at physical insight into this interaction, is presented. Results in the plane wave region for the so called scattering matrix for a sudden area expansion with flow in cylindrical pipes are compared with experimental values. Both the magnitude and the phase, in the form of an end correction, is presented. The model is also compared to a 2 dimensional model, in order to evaluate the anticipated increased accuracy of the 3 dimensional modeling. The scattering coefficients are strongly dependent on the flow speed, which is up to a Mach number of 0.5. It is observed that for low frequencies, the interaction is dominated by the dynamics of an unstable shear layer downstream of the edges. For higher frequencies, the wave propagation is mainly affected by convective effects. Differences in properties for the 2D and the 3D cases are also explored.

This paper proposes a new two dimensional (2D) analytical model for a germanium (Ge) single gate silicon-on-insulator tunnel field effect transistor (SG SOI TFET). The parabolic approximation technique is used to solve the 2D Poisson equation with suitable boundary conditions and analytical expressions are derived for the surface potential, the electric field along the channel and the vertical electric field. The device output tunnelling current is derived further by using the electric fields. The results show that Ge based TFETs have significant improvements in on-current characteristics. The effectiveness of the proposed model has been verified by comparing the analytical model results with the technology computer aided design (TCAD) simulation results and also comparing them with results from a silicon based TFET.

Validation of cell voltage and water content in a PEM (polymer electrolyte membrane) fuel cell model using neutron imaging for different operating conditions

A Numerical and experimental study of thermal and heat transfer processes in a steam condenser operating in steam power plant with steam engine was developed to built analytical model using to predict thermal profile of condenser. Iterative technique between Engineering Equations Solver (EES) and Matlab programming was developed to find water properties .The exit water temperature, steam flow rate, geometric dimension (diameter and tube length) ,convection heat transfer coefficient of water and condenser efficiency were computed using the analytic model. Experimental results for a range of water flow rate (0.0153 to 0.0121 kg/s) with constant inlet water temperature of 25 were used to validate the analytical model. Compared with a validated model, the standard deviations of analytical model are less than 4%, and all errors fall into ±6%. Analytical model can be used to show the relation between thermal parameters.

Analytical and computational models are constructed for predicting the temperature distribution in a workpiece during gas metal arc braze-welding (GMABW). Specifically, the weld zone is modeled with Rosenthal’s analytical model, a finite difference model (FDM) and a finite volume computational model, constructed in the FLUENT® software package. Each model relates controllable braze-welding process parameters, such as traverse speed and applied voltage, to the temperature field that develops during the braze-welding process. Model-based predictions are validated by comparison with experimental data obtained from braze-welded specimens of C22000 commercial bronze alloy (CuZn90/10%wt). Temperature data are collected during the braze-welding process via thermocouples and infrared pyrometers aimed at the top surface of the specimen. Recommendations are made regarding the range of applicability and limitations of the models. In addition, opportunities are discussed for applying these models as part of an automated control framework for GMABW.

SummaryOne‐dimensional mathematical models for vapor‐phase volatile organic compound (VOC) diffusion through composite cover barriers are presented. An analytical solution to the model was obtained by the method of separation of variables. The results obtained by the proposed solution agree well with those obtained by a numerical analysis. Based on the proposed analytical model, the VOC breakthrough curves of five different composite covers are compared. The effects of degree of saturation of geosynthetic clay liner (GCL) or compacted clay liner (CCL) on VOC migration in the composite covers are then presented. Results show that the composite cover barriers provide much better diffusion barriers for VOC than the single CCL. The top surface steady‐state flux for a composite barrier, consisting of a 1.5 mm geomembrane (GM) and a 20 cm CCL, can be 8.3 times lower than that for a 30 cm CCL. The surface steady‐state flux for the case with (1.5 mm GM + 6 mm GCL) was found to be 2.3 times lower than that for the case with (1.5 mm GM + 20 cm CCL). The degree of saturation Sr of the CCL has a great influence on VOC migration in composite covers when Sr is larger than 0.5. The steady‐state flux at the surface of GM for the case with Sr = 0.7 can be 1.8 times lower than that for the case with Sr = 0.2. The proposed analytical model is relatively simple and can be used for verification of complicated numerical models, analysis of experimental data and performance assessment of composite cover barriers. Copyright © 2016 John Wiley & Sons, Ltd.