scholarly journals Using the Weak-Temperature Gradient Approximation to Evaluate Parameterizations: An Example of the Transition From Suppressed to Active Convection

2017 ◽  
Vol 9 (6) ◽  
pp. 2350-2367 ◽  
Author(s):  
C. L. Daleu ◽  
R. S. Plant ◽  
S. J. Woolnough
Keyword(s):  
Temperature Gradient ◽  
Active Convection

scholarly journals Transition from Suppressed to Active Convection Modulated by a Weak Temperature Gradient–Derived Large-Scale Circulation

2015 ◽  
Vol 72 (2) ◽  
pp. 834-853 ◽  
Author(s):  
C. L. Daleu ◽  
S. J. Woolnough ◽  
R. S. Plant
Keyword(s):  
Temperature Gradient ◽  
Large Scale ◽  
Deep Convection ◽  
Potential Temperature ◽  
Mean Value ◽  
Transition Time ◽  
Large Scale Circulation ◽  
Transition Times ◽  
Active Convection ◽  
Fully Coupled

Abstract Numerical simulations are performed to assess the influence of the large-scale circulation on the transition from suppressed to active convection. As a model tool, the authors used a coupled-column model. It consists of two cloud-resolving models that are fully coupled via a large-scale circulation that is derived from the requirement that the instantaneous domain-mean potential temperature profiles of the two columns remain close to each other. This is known as the weak temperature gradient approach. The simulations of the transition are initialized from coupled-column simulations over nonuniform surface forcing, and the transition is forced in the dry column by changing the local and/or remote surface forcings to uniform surface forcing across the columns. As the strength of the circulation is reduced to zero, moisture is recharged into the dry column and a transition to active convection occurs once the column is sufficiently moistened to sustain deep convection. Direct effects of changing surface forcing occur over the first few days only. Afterward, it is the evolution of the large-scale circulation that systematically modulates the transition. Its contributions are approximately equally divided between the heating and moistening effects. A transition time is defined to summarize the evolution from suppressed to active convection. It is the time when the rain rate in the dry column is halfway to the mean value obtained at equilibrium over uniform surface forcing. The transition time is around twice as long for a transition that is forced remotely compared to a transition that is forced locally. Simulations in which both local and remote surface forcings are changed produce intermediate transition times.

Technical Note. Influence of Material Used for the Regenerator on the Properties of a Thermoacoustic Heat Pump

2013 ◽  
Vol 38 (4) ◽  
pp. 565-570 ◽  
Author(s):  
Bartłomiej Kruk
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Acoustic Wave ◽  
Heat Pump ◽  
Sound Wave ◽  
Heat Exchangers ◽  
Heat Pumps ◽  
Technical Note ◽  
New Materials ◽  
Modern Technologies

Abstract Research in termoacoustics began with the observation of the heat transfer between gas and solids. Using this interaction the intense sound wave could be applied to create engines and heat pumps. The most important part of thermoacoustic devices is a regenerator, where press of conversion of sound energy into thermal or vice versa takes place. In a heat pump the acoustic wave produces the temperature difference at the two ends of the regenerator. The aim of the paper is to find the influence of the material used for the construction of a regenerator on the properties of a thermoacoustic heat pump. Modern technologies allow us to create new materials with physical properties necessary to increase the temperature gradient on the heat exchangers. The aim of this paper is to create a regenerator which strongly improves the efficiency of the heat pump.

Field distribution in polymeric MV-HVDC model cable under temperature gradient. Simulation and space charge measurements

2014 ◽  
Vol 17 (5-6) ◽  
pp. 307-325 ◽  
Author(s):  
Thi Thu Nga Vu ◽  
Gilbert Teyssedre ◽  
Bertrand Vissouvandin ◽  
Séverine Le Roy ◽  
Christian Laurent ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Space Charge ◽  
Field Distribution

SIMULATION OF THE CURRENT-VOLTAGE CHARACTERISTICS OF SOLAR BATTERIES WITH CONSIDERING DECREASE OF LIGHTING DUE TO THE INFLUENCE OF JETS OF THE ELECTRIC PROPULSION

2019 ◽  
pp. 56-64
Author(s):  
Ya.N. MIGUNOV ◽  
V.V. ONUFRIEV
Keyword(s):  
Solar Cells ◽  
Temperature Gradient ◽  
Electric Propulsion ◽  
Protective Coatings ◽  
Rocket Engine ◽  
Solar Array ◽  
Rocket Engines ◽  
Lighting Conditions ◽  
Main Equation ◽  
Voltage Current Characteristic

A model for calculating the voltage-current characteristic of a solar array in the presence of a temperature gradient by its photovoltaic converters and their variable illumination due to possible pollution under the action of space factors, including operation of electric rocket engines, is described. The model is based on the main equation of a solar cell. In this case both a one-dimensional and a two-dimensional temperature gradients are taken into account. The principles of constructing a model are given, and the initial data selection is made. To simulate the lighting conditions of the solar array such a concept as effective illumination is used, i.e. the density of the radiation flux which falls on photovoltaic converters passing through the protective coatings. The features of simulation of the temperature distribution in the solar array and the effective illumination of its surface in cases of parallel, serial and mixed switching of solar cells are described. The calculation procedures and examples of solar cells are given. The construction of the model in universal mathematical package Mathcad is described. Some simulation results are discussed. Key words: solar array, mathematical simulation, illumination, temperature gradient, electric rocket engine, spacecraft, Mathcad.

EFFECTS OF TEMPERATURE GRADIENT ON LAMELLAR ORIENTATIONS OF DIRECTIONAL SOLIDIFIED TiAl--BASED ALLOY

2011 ◽  
Vol 46 (10) ◽  
pp. 1223-1229 ◽  
Author(s):  
Zhixia XIAO ◽  
Lijing ZHENG ◽  
Lili YANG ◽  
Jie YAN ◽  
Hu ZHANG
Keyword(s):  
Temperature Gradient ◽  
Effects Of Temperature
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