Modeling of Moisture Transport Into an Electronic Enclosure Using the Resistor-Capacitor Approach

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Ž. Staliulionis ◽  
H. Conseil-Gudla ◽  
S. Mohanty ◽  
M. Jabbari ◽  
R. Ambat ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Moisture Transport ◽  
Initial Conditions ◽  
Computation Time ◽  
Second Law ◽  
Temperature Changes ◽  
One Dimensional ◽  
Isothermal Conditions ◽  
Rc Circuit ◽  
The Impact

Abstract The aim of this paper is to model moisture ingress into a closed electronic enclosure under isothermal and non-isothermal conditions. As a consequence, an in-house code for moisture transport is developed using the Resistor-Capacitor (RC) method, which is efficient as regards computation time and resources. First, an in-house code is developed to model moisture transport through the enclosure walls driven by diffusion, which is based on the Fick's first and second law. Thus, the model couples a lumped analysis of moisture transport into the box interior with a modified one-dimensional (1D) analogy of Fick's second law for diffusion in the walls. Thereafter, under non-isothermal conditions, the moisture RC circuit is coupled with the same configuration of thermal RC circuit. The paper concerns the study of the impact of imperfections in the enclosure for the whole diffusion process. Moreover, a study of the impact of wall thickness, different diffusion coefficient, and initial conditions in the wall for the moisture transport is accomplished. Comparison of modeling and experimental results showed that the RC model is very applicable for simple and rough enclosure design. Furthermore, the experimental and modeling results indicate that the imperfections, with certain limits, do not have a significant effect on the moisture transport. The modeling of moisture transport under non-isothermal conditions shows that the internal moisture oscillations follow ambient temperature changes albeit with a delay. Although, moisture ingress is slightly dependent on ambient moisture oscillations; however, it is not so dominant until equilibrium is reached.

scholarly journals Mathematical modeling of temperature changes impact on artificial ice islands

2021 ◽  
Vol 13 (1) ◽  
pp. 79-86
Author(s):  
Maxim V. Muratov ◽  
◽  
Vladimir A. Biryukov ◽  
Denis S. Konov ◽  
Igor B. Petrov ◽  
...  
Keyword(s):  
Numerical Solution ◽  
Stefan Problem ◽  
Initial Conditions ◽  
Economic Feasibility ◽  
The Arctic ◽  
Seasonal Temperature ◽  
Time Step ◽  
Temperature Changes ◽  
The Stability ◽  
The Impact

The article is devoted to the numerical solution of the Stefan problem for thermal effects on an artificial ice island. For modern tasks of the development of the Arctic, associated with the exploration and production of minerals, it is important to create artificial ice islands in the Arctic shelf, due to the speed of their construction, economic feasibility and other factors. The most important task for the exploitation of such islands is their stability, including against melting. This paper discusses the issue of the stability of ice islands to melting. For this, the Stefan problem on the change in the phase state of matter is formulated. An enthalpy solution method is constructed, and the applicability of this method is considered. For the numerical solution, the Peasman-Reckford scheme is used, which is unconditionally spectrally stable in the two-dimensional case, which allows to freely choose the time step. In addition, the developed approach takes into account the flow of water and the flow of melted water, which is important in the task at hand. The developed computational algorithms are parallelized for use on modern multiprocessor computing systems An approach is implemented for modeling thermal processes in the thickness of an arbitrary mass of substances, taking into account arbitrary initial conditions, environmental conditions, tidal currents of water, and solar radiation. This approach was used to calculate the temperature distribution in the thickness of the ice island, as well as to study the impact of seasonal temperature changes on the stability of the island.

The Dissipation Function-Based Efficiency for Turbomachinery: Part 1 — The Efficiency of a Cooled Turbine Row

2014 ◽  
Author(s):  
Chong M. Cha
Keyword(s):  
Aerodynamic Performance ◽  
Dissipation Function ◽  
Second Law ◽  
Efficiency Measure ◽  
One Dimensional ◽  
Specific Heats ◽  
Gas Streams ◽  
The One ◽  
The Impact ◽  
Mixing Problem

The effect of coolant addition or “mixing loss” on aerodynamic performance is formulated for the turbine, where mixing takes place between gas streams of different compositions as well as static temperatures. To do this, a second law efficiency measure is applied to a generalization of the one-dimensional mixing problem between a main gas stream and a single coolant feed, first introduced and studied by Hartsel [1] for the turbine application. Hartsel’s 1972 model for mass-transfer cooling loss still remains the standard for estimating mixing loss in today’s turbines. The present generalization includes losses due to the additional contributions of “compositional mixing” (mixing between unlike compositions of the main and coolant streams) as well as the effect of chemical reaction between the two streams. Scaling of the present dissipation function-based loss model to the mainstream Mach number and relative cooling massflow and static temperature is given. Limitations of the constant specific heats assumptions and the impact of fuel-to-air ratio are also quantified.

scholarly journals SL9 impact chemistry: Long-term photochemical evolution

1996 ◽  
Vol 156 ◽  
pp. 243-268 ◽  
Author(s):  
Julianne I. Moses
Keyword(s):  
Initial Conditions ◽  
Model Data ◽  
Initial Composition ◽  
One Dimensional ◽  
Photochemical Processes ◽  
Model Predictions ◽  
The Impact ◽  
Over Time ◽  
Photochemical Models

One-dimensional photochemical models are used to provide an assessment of the chemical composition of the Shoemaker-Levy 9 impact sites soon after the impacts, and over time, as the impact-derived molecular species evolve due to photochemical processes. Photochemical model predictions are compared with the observed temporal variation of the impact-derived molecules in order to place constraints on the initial composition at the impact sites and on the amount of aerosol debris deposited in the stratosphere. The time variation of NH3, HCN, OCS, and H2S in the photochemical models roughly parallels that of the observations. S2persists too long in the photochemical models, suggesting that some of the estimated chemical rates constants and/or initial conditions(e.g., the assumed altitude distribution or abundance of S2) are incorrect. Models predict that CS and CO persist for months or years in the jovian stratosphere. Observations indicate that the model results with regard to CS are qualitatively correct (although the measured CS abundance demonstrates the need for a larger assumed initial abundance of CS in the models), but that CO appears to be more stable in the models than is indicated by observations. The reason for this discrepancy is unknown. We use model-data comparisons to learn more about the unique photochemical processes occurring after the impacts.

scholarly journals Impact of Tropical Storm Bopha on the Intensity Change of Super Typhoon Saomai in the 2006 Typhoon Season

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Hongxiong Xu ◽  
Xuejin Zhang ◽  
Xiangde Xu
Keyword(s):  
Moisture Transport ◽  
Initial Conditions ◽  
Mainland China ◽  
Tropical Storm ◽  
Intensity Change ◽  
Super Typhoon ◽  
Direction Change ◽  
Typhoon Season ◽  
The Impact ◽  
Typhoon Saomai

Super Typhoon Saomai (2006, 08W), which caused historical disaster in the landfall region, is the most powerful typhoon ever making landfall in Mainland China since 1949. The impact of Tropical Storm Bopha (2006, 10W) on Saomai is regarded as a binary tropical cyclone (TC) interaction. In order to quantify the influence of Bopha on the intensity of Saomai, a set of numerical experiments are performed by artificially modifying the intensity of Bopha in its initial conditions. It is shown that changing the intensity of Bopha has significant effects on simulating Saomai’s intensities, structures, and tracks. We find that moisture transport is a pivotal process of binary TC interaction. It is interesting that there are opposite effects by Bopha at different development stages of Saomai. The existence of Bopha and increasing its intensity would weaken Saomai at its intensifying stage while intensifying Saomai at its weakening stage. A possible explanation of these effects is the direction change of moisture transport from/to Saomai at its intensifying/weakening stages through the channel. It may suggest a significant relevance for operational intensity forecasts under active binary TC interaction.

Theoretical Model of Crater Wear

1971 ◽  
Vol 93 (4) ◽  
pp. 1051-1056 ◽  
Author(s):  
Yong-Son Lee
Keyword(s):  
Diffusion Coefficient ◽  
Theoretical Model ◽  
Temperature Distribution ◽  
Boundary Conditions ◽  
Second Law ◽  
Crater Wear ◽  
One Dimensional ◽  
Step Functions ◽  
Contact Surfaces ◽  
Infinite Media

A one dimensional mass diffusion equation including the first derivatives with respect to the coordinates in Fick’s second law is considered. The diffusion coefficient is also considered, as a function of temperature distribution in a semi-infinite media under certain boundary conditions. Since the boundary conditions for both temperature and concentration on the contact surfaces are not a well defined function, the solutions are approximated by dividing the boundary conditions into several well defined functions, such as step functions, and then superimposed. The results obtained by the present analysis are compared with the empirical results of other investigators.

scholarly journals Data assimilation in a sparsely observed one-dimensional modeled MHD system

2007 ◽  
Vol 14 (2) ◽  
pp. 181-192 ◽  
Author(s):  
Z. Sun ◽  
A. Tangborn ◽  
W. Kuang
Keyword(s):  
Magnetic Field ◽  
Data Assimilation ◽  
Magnetic Fields ◽  
Initial Conditions ◽  
Positive Impact ◽  
Optimal Interpolation ◽  
One Dimensional ◽  
Mhd System ◽  
The Impact ◽  
The Magnetic Field

Abstract. A one dimensional non-linear magneto-hydrodynamic (MHD) system has been introduced to test a sequential optimal interpolation assimilation technique that uses a Monte-Carlo method to calculate the forecast error covariance. An ensemble of 100 model runs with perturbed initial conditions are used to construct the covariance, and the assimilation algorithm is tested using Observation Simulation Experiments (OSE's). The system is run with a variety of observation types (magnetic and/or velocity fields) and a range of observation densities. The impact of cross covariances between velocity and magnetic fields is investigated by running the assimilation with and without these terms. Sets of twin experiments show that while observing both velocity and magnetic fields has the greatest positive impact on the system, observing the magnetic field alone can also effectively constrain the system. Observations of the velocity field are ineffective as a constraint on the magnetic field, even when observations are made at every point. The implications for geomagnetic data assimilation are discussed.

Methods for Restricting Maximum Exposure Rate in Computerized Adaptative Testing

Methodology ◽  
2007 ◽  
Vol 3 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Juan Ramon Barrada ◽  
Julio Olea ◽  
Vicente Ponsoda
Keyword(s):  
Measurement Accuracy ◽  
Computerized Adaptive Testing ◽  
Computation Time ◽  
Adaptive Testing ◽  
Exposure Rate ◽  
Control Parameters ◽  
The Impact ◽  
Two Alternatives ◽  
Selection Of ◽  
Maximum Exposure

Abstract. The Sympson-Hetter (1985) method provides a means of controlling maximum exposure rate of items in Computerized Adaptive Testing. Through a series of simulations, control parameters are set that mark the probability of administration of an item on being selected. This method presents two main problems: it requires a long computation time for calculating the parameters and the maximum exposure rate is slightly above the fixed limit. Van der Linden (2003) presented two alternatives which appear to solve both of the problems. The impact of these methods in the measurement accuracy has not been tested yet. We show how these methods over-restrict the exposure of some highly discriminating items and, thus, the accuracy is decreased. It also shown that, when the desired maximum exposure rate is near the minimum possible value, these methods offer an empirical maximum exposure rate clearly above the goal. A new method, based on the initial estimation of the probability of administration and the probability of selection of the items with the restricted method ( Revuelta & Ponsoda, 1998 ), is presented in this paper. It can be used with the Sympson-Hetter method and with the two van der Linden's methods. This option, when used with Sympson-Hetter, speeds the convergence of the control parameters without decreasing the accuracy.

scholarly journals Experimental study of the supercritical CO 2 diffusion coefficient in porous media under reservoir conditions

2019 ◽  
Vol 6 (6) ◽  
pp. 181902 ◽  
Author(s):  
Junchen Lv ◽  
Yuan Chi ◽  
Changzhong Zhao ◽  
Yi Zhang ◽  
Hailin Mu
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Oil Recovery ◽  
Carbon Capture ◽  
Carbon Capture And Storage ◽  
Elevated Pressure ◽  
Experimental Results ◽  
Saturated Porous Media ◽  
Reservoir Conditions ◽  
The Impact

Reliable measurement of the CO 2 diffusion coefficient in consolidated oil-saturated porous media is critical for the design and performance of CO 2 -enhanced oil recovery (EOR) and carbon capture and storage (CCS) projects. A thorough experimental investigation of the supercritical CO 2 diffusion in n -decane-saturated Berea cores with permeabilities of 50 and 100 mD was conducted in this study at elevated pressure (10–25 MPa) and temperature (333.15–373.15 K), which simulated actual reservoir conditions. The supercritical CO 2 diffusion coefficients in the Berea cores were calculated by a model appropriate for diffusion in porous media based on Fick's Law. The results show that the supercritical CO 2 diffusion coefficient increases as the pressure, temperature and permeability increase. The supercritical CO 2 diffusion coefficient first increases slowly at 10 MPa and then grows significantly with increasing pressure. The impact of the pressure decreases at elevated temperature. The effect of permeability remains steady despite the temperature change during the experiments. The effect of gas state and porous media on the supercritical CO 2 diffusion coefficient was further discussed by comparing the results of this study with previous study. Based on the experimental results, an empirical correlation for supercritical CO 2 diffusion coefficient in n -decane-saturated porous media was developed. The experimental results contribute to the study of supercritical CO 2 diffusion in compact porous media.

scholarly journals On Kaufmann's theory of the impact of the pianoforte hammer

1920 ◽  
Vol 97 (682) ◽  
pp. 99-110 ◽  
Keyword(s):  
Initial Conditions ◽  
Practical Importance ◽  
Prima Facie ◽  
Point Of View ◽  
Infinite Length ◽  
Modes Of Vibration ◽  
Rigorous Treatment ◽  
The Subject ◽  
Set Up ◽  
The Impact

The theory of the vibrations of the pianoforte string put forward by Kaufmann in a well-known paper has figured prominently in recent discussions on the acoustics of this instrument. It proceeds on lines radically different from those adopted by Helmholtz in his classical treatment of the subject. While recognising that the elasticity of the pianoforte hammer is not a negligible factor, Kaufmann set out to simplify the mathematical analysis by ignoring its effect altogether, and treating the hammer as a particle possessing only inertia without spring. The motion of the string following the impact of the hammer is found from the initial conditions and from the functional solutions of the equation of wave-propagation on the string. On this basis he gave a rigorous treatment of two cases: (1) a particle impinging on a stretched string of infinite length, and (2) a particle impinging on the centre of a finite string, neither of which cases is of much interest from an acoustical point of view. The case of practical importance treated by him is that in which a particle impinges on the string near one end. For this case, he gave only an approximate theory from which the duration of contact, the motion of the point struck, and the form of the vibration-curves for various points of the string could be found. There can be no doubt of the importance of Kaufmann’s work, and it naturally becomes necessary to extend and revise his theory in various directions. In several respects, the theory awaits fuller development, especially as regards the harmonic analysis of the modes of vibration set up by impact, and the detailed discussion of the influence of the elasticity of the hammer and of varying velocities of impact. Apart from these points, the question arises whether the approximate method used by Kaufmann is sufficiently accurate for practical purposes, and whether it may be regarded as applicable when, as in the pianoforte, the point struck is distant one-eighth or one-ninth of the length of the string from one end. Kaufmann’s treatment is practically based on the assumption that the part of the string between the end and the point struck remains straight as long as the hammer and string remain in contact. Primâ facie , it is clear that this assumption would introduce error when the part of the string under reference is an appreciable fraction of the whole. For the effect of the impact would obviously be to excite the vibrations of this portion of the string, which continue so long as the hammer is in contact, and would also influence the mode of vibration of the string as a whole when the hammer loses contact. A mathematical theory which is not subject to this error, and which is applicable for any position of the striking point, thus seems called for.

Sign in / Sign up

Export Citation Format

Share Document