The Influence to Thermal Resistance to Conduction in Rotary Regenerators

2002 ◽  
Author(s):  
Carlos E. L. No´brega ◽  
Ni´sio C. L. Brum ◽  
William Worek
Keyword(s):  
Mathematical Model ◽  
Thermal Resistance ◽  
Substantial Reduction ◽  
Storage Material ◽  
Simplifying Assumptions

The present work is devoted to the modeling of rotary regenerators. A mathematical model is proposed based on a number of simplifying assumptions, the validity of which is discussed in light of actual regenerator design figures. The results are presented in ε-NTU analysis. It is shown that the often neglected thermal resistance offered by the storage material might imply in substantial reduction on the regenerator effectiveness.

scholarly journals MATHEMATICAL MODELLING OF RUNNING CROWN FOREST FIRES

2010 ◽  
Vol 15 (2) ◽  
pp. 161-174 ◽  
Author(s):  
Dmitry Barovik ◽  
Valery Taranchuk
Keyword(s):  
Mathematical Model ◽  
Forest Fire ◽  
Forest Fires ◽  
Computer Modelling ◽  
Fire Behaviour ◽  
Fire Propagation ◽  
Finite Difference Approximations ◽  
Difference Approximations ◽  
Simplifying Assumptions ◽  
Crown Forest

Adapted mathematical model for simulation of running crown forest fire propagation is considered. Simplifying assumptions, equations of the model, initial and boundary conditions, finite difference approximations are introduced. The results of computer modelling and the peculiarities of forest fire behaviour in heterogeneous forests are discussed.

scholarly journals Parametric Method For Evaluating Optimal Ship Deadweight

2014 ◽  
Vol 21 (2) ◽  
pp. 3-8
Author(s):  
Jan P. Michalski
Keyword(s):  
Mathematical Model ◽  
Closed Form ◽  
Parametric Method ◽  
Freight Rate ◽  
Ship Design ◽  
Design Parameters ◽  
Optimal Value ◽  
Simplifying Assumptions ◽  
The Mathematical Model ◽  
Economic Measure

Abstract The paper presents a method of choosing the optimal value of the cargo ships deadweight. The method may be useful at the stage of establishing the main owners requirements concerning the ship design parameters as well as for choosing a proper ship for a given transportation task. The deadweight is determined on the basis of a selected economic measure of the transport effectiveness of ship - the Required Freight Rate (RFR). The mathematical model of the problem is of a deterministic character and the simplifying assumptions are justified for ships operating in the liner trade. The assumptions are so selected that solution of the problem is obtained in analytical closed form. The presented method can be useful for application in the pre-investment ships designing parameters simulation or transportation task studies.

Thermal Analysis of High Efficiency High Speed Drives

2019 ◽  
Author(s):  
Yasmin Khakpour ◽  
Weilun Warren Chen ◽  
Parikshith Channegowda ◽  
Matthew R. Pearson ◽  
Yongduk Lee ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Thermal Resistance ◽  
Power Electronics ◽  
Thermal Management ◽  
High Speed ◽  
High Efficiency ◽  
Management Strategies ◽  
Substantial Reduction ◽  
Operating Conditions ◽  
Heat Conducting

Abstract The thermal management of the PCB based power electronics is a key element to ensure safe operating conditions and to meet lifetime, reliability and safety requirements. This is challenging for applications above 1 kW because the substrate material used in a PCB such as FR-4 has very low heat conducting properties. Hence, there is a limit on how much loss can be dissipated from the board and for that reason this approach has only been adopted in the industry for very low power applications. With the proposed multilevel topology, WBG devices, and innovative thermal management strategies it is possible to expand the PCB based power electronics approach to power ratings between 1kW and 10 kW. For instance, an improvement in the thermal resistance of the PCB can be obtained by soldering a discrete WBG device with a TO-263 package directly on a PCB with about one inch square copper area around the device which will act as a heat spreader. Then, a further substantial reduction in the thermal resistance of a PCB is possible by the application of electrical vias. In principle each via is a copper sleeve through the board or through a part of the board. Where, instead of using its electrical function, a via can also be used as a thermal conductor. In this work, the thermal analysis of the PCB and the effect of number of vias as well as the effect of filling the vias with a thermally conductive material has been studied. The design has been optimized for the number of vias and the modeling results have been verified with experimental tests.

THERMAL RESISTANCE OF POWER SEMICONDUCTOR MODULES OF SOLDERED CONSTRUCTION

2020 ◽  
Vol 5 ◽  
pp. 122-130
Author(s):  
S.I. MATYUKHIN ◽  
D.O. MALYI ◽  
A.S. VISHNYAKOV ◽  
E.Yu. ORLOV ◽  
V.I. KAZAKOV
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Computer Simulation ◽  
Thermal Resistance ◽  
Comsol Multiphysics ◽  
Power Semiconductor ◽  
Transfer Processes ◽  
Main Effect

The heat transfer processes in power semiconductor modules of soldered construction are studied using the methods of computer simulation in Comsol Multiphysics software. The problem of the thermal resistance of such modules is solved. The factors showing the main effect on the thermal resistance of the modules are studied. A mathematical model allowing engineering calculations of this resistance is developed.

scholarly journals On firework blasts and qualitative parameter dependency

2016 ◽  
Vol 472 (2185) ◽  
pp. 20150720 ◽  
Author(s):  
T. I. Zohdi
Keyword(s):  
Mathematical Model ◽  
Kinetic Energy ◽  
Time Evolution ◽  
Three Dimensional ◽  
Simplifying Assumptions ◽  
Released Energy ◽  
Detonation Energy ◽  
Parameter Dependency ◽  
Blast Pulse ◽  
Qualitative Parameter

In this paper, a mathematical model is developed to qualitatively simulate the progressive time-evolution of a blast from a simple firework. Estimates are made for the blast radius that one can expect for a given amount of detonation energy and pyrotechnic display material. The model balances the released energy from the initial blast pulse with the subsequent kinetic energy and then computes the trajectory of the material under the influence of the drag from the surrounding air, gravity and possible buoyancy. Under certain simplifying assumptions, the model can be solved for analytically. The solution serves as a guide to identifying key parameters that control the evolving blast envelope. Three-dimensional examples are given.

scholarly journals Development of a Mathematical Model for Simulation of Macroalgae Farming in the Coastal Areas

2018 ◽  
Vol 23 (1) ◽  
pp. 32
Author(s):  
Abdolmajid Lababpour
Keyword(s):  
Mathematical Model ◽  
Initial Conditions ◽  
Farming System ◽  
The Finite Element Method ◽  
Batch Mode ◽  
Predictive Values ◽  
Simplifying Assumptions ◽  
Model Equations ◽  
Bandar Abbas ◽  
The Impact

A mathematical model consisting of a system of three coupled partial differential equations (PDEs) was proposed to estimate the concentrations of nitrogen, phosphorous and macroalgae biomass in coastal open waters. However, some simplifying assumptions were used in the model to cope with the complexity of real conditions. For the macroalgae biomass, the system works as a batch mode, while input and output were accounted for nitrogen and phosphorous. The MATLAB pdepe feature, applying the finite element method was used in model solving and the simulation of model equations. The program was split into four functions that included the solver and post-processing of the results, a function containing the PDEs, a function setting the initial conditions, and one setting the boundary conditions. For model validation, the experimental measurement of nitrogen, phosphorous and macroalgae biomass concentrations of Bandar Abbas coastal open waters were analyzed by standard methods at three depths of 1, 5 and 10 m. The predictive values of the developed model demonstrated its applicability for the management of coastal macroalgae cultivation systems by assessing the impact of nitrogen and phosphorous strategies on the farming system.

scholarly journals Безразмерная математическая модель термоэлектрического охладителя: режим Delta T-=SUB=-max-=/SUB=-

2019 ◽  
Vol 53 (5) ◽  
pp. 635
Author(s):  
А.А. Мельников ◽  
О.М. Тарасов ◽  
А.В. Чеков ◽  
М.А. Башкин
Keyword(s):  
Thermal Conductivity ◽  
Mathematical Model ◽  
Thermal Resistance ◽  
Thermoelectric Cooler ◽  
Leg Length ◽  
Additional Increase ◽  
Optimal Current ◽  
Output Characteristics ◽  
Positive Effect ◽  
Determining Factor

AbstractThe thermal resistances on the cold and hot sides substantially affect the output characteristics of thermoelectric devices. A dimensionless mathematical model of a thermoelectric cooler, which makes it possible to calculate device parameters, such as the optimal thermal resistance ratio on the cold and hot sides as well as the optimal current taking into account the influence of thermal resistances, is presented. The maximal temperature difference Δ T _max mode is considered. It is shown that the optimal cooler parameters are different for implementation of the Δ T _max and Q _max modes. The determining factor for the Δ T _max mode is the influence of the thermal resistance on the hot side, and the optimal current is 0.4–0.7 of the maximal current in most cases for the material with ZT = 1. It is shown that an additional increase in Δ T _max of a cooler is attained with a decrease in the thermal conductivity of the thermoelectric material due to a decrease in the influence of the thermal resistance on the hot side besides the effect from an increase in ZT . An increase in the length of thermoelectric legs has the same positive effect of an increase in Δ T _max of a cooler, while a decrease in the leg length negatively affects Δ T _max.

scholarly journals INFLUENCE OF THERMAL RESISTANCE OF AIR CONDENSER TUBES ON STEAM COOLING EFFICIENCY

2020 ◽  
Author(s):  
J. Jianguo ◽  
G. Varlamov ◽  
K. Romanova ◽  
L. Suxiang ◽  
L. Zhigang
Keyword(s):  
Mathematical Model ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Cooling System ◽  
Steam Pressure ◽  
Operating Conditions ◽  
Air Cooling ◽  
Cooling Unit ◽  
Air Condenser ◽  
Working Bodies

The research is carried out using a mathematical model of conditions and features of condensation processes with the influence of changes in internal and external thermal resistances of working bodies, which occur during contamination of outside and inside metal pipes of heat exchange surfaces of air condenser. capacitor. Particular attention is paid to the selection, detailing and determination of more than twenty basic parameters that characterize the operation of the direct cooling unit of the condensing unit for the summer, the conditions of heat transfer processes between the working bodies taking into account the finned outer surface of elliptical condenser tubes. The results of experiments on the mathematical model are analyzed and the influence of the incoming air velocity and ambient temperature on the output steam pressure in the condenser direct air cooling system within the change of internal and external thermal resistances in the range 0-0.001(m2·K)/W due to cooling tube contamination is determined. air condenser steam turbine installation. Conditions, character and features of influence of thermal resistance of pollution in cooling tubes on steam pressure at an exit from them are defined, the basic factors defining steam pressure at an exit, necessity of the organization of control of thermal resistance of pollution in a pipe during unit operation at variable operating conditions and expediency is substantiated. conducting test studies of operating modes while taking into account the influence of thermal resistance of external and internal pollution on the thermal efficiency of the cooling unit. Studies have shown that at a fixed value of the heat load of the exhaust steam, the pressure of the steam outlet increases with increasing ambient temperature and decreasing the speed of the incoming air.

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