Search query: consistency of cooling temperature

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abstract: The adequacy of the model of high temperature precipitation in dislocation free silicon single crystals to the classical theory of nucleation and growth of second phase particles in solids has been considered. It has been shown that the introduction and consideration of thermal conditions of crystal growth in the initial equations of the classical nucleation theory make it possible to explain the precipitation processes occurring in the high temperature range and thus extend the theoretical basis of the application of the classical nucleation theory. According to the model of high temperature precipitation, the smallest critical radius of oxygen and carbon precipitates is observed in the vicinity of the crystallization front. Cooling of the crystal is accompanied by the growth and coalescence of precipitates. During heat treatments, the nucleation of precipitates starts at low temperatures, whereas the growth and coalescence of precipitates occur with an increase in the temperature. It has been assumed that the high temperature precipitation of impurities can determine the overall kinetics of defect formation in other dislocation free single crystals of semiconductors and metals.
author_names: Vitalyi Igorevich Talanin

I E Talanin
title: On the problem of the consistency of the high temperature precipitation model with the classical nucleation theory
year: 2014

abstract: It is known that the weld metal mechanical properties of quenched and tempered steels are dependent upon cooling rate, which is presently indirectly controlled by specification of heat input. A method to directly control weld metal cooling rate would result in more consistency in achieving required mechanical properties. In the present investigation the use of commercial infrared sensing equipment was explored as a means of real time monitoring of weld metal cooling rate. Infrared equipment has a distinct advantage over other temperature detecting systems in that it requires no physical contact with the work, thus affording a minimum amount of interference with the welding process, and is therefore a potentially useful detector for an adaptive feedback welding control system based on cooling rate. It was found that infrared thermography appears to offer considerable promise for welding control by providing weld metal cooling rates which are: (1) reproducible, (2) sensitive to variations in welding conditions, and (3) relatable to cooling rates as measured by plunged thermocouples. ADMINISTRATIVE INFORMATION This report was prepared under Work Unit 2822 130, Program Element 61152N, project ZR00001, titled, "Feedback Control of Arc Welding," as part of the Center Independent Rc~erch Program, managed by the Technical Director, Dr. A. Powell. The work reported herein was conducted under the supervision of Mr. F. J. Lengenfelder, Head, Titanium and Nonferrous Metals Fabrication Branch, and Mr. A. Pollack, Head, Ferrous Metals Fabrication Branch. ACKNOWLEDGMENT The authors wish to acknowledge Dr. I. Kramer, Code 2802, of this Center for technical guidance in support of this project.
title: INFRARED TEMPERATURE SENSING OF COOLING RATES FOR ARC WELDING C ETC(U)

abstract: Abstract The efficiency of photovoltaic modules depends mainly on the cell operating temperatures. Performance enhancement of building integrated photovoltaic (BIPV) panels by passive cooling has been investigated both experimentally and with computational modeling. It has been shown that mounting the BIPV with a narrow channel can reduce the operating temperature of the photovoltaic panel. This enhancement in the heat transfer from the PV panel results in decreasing the average temperature of the PV panel from 5 to 10 degC. Results show that having a 30 cm channel beneath the panel can increase the electrical output by 3 4% This increase in PV output can translate into a significant amount over the life cycle of a given PV module. Various channel aspect ratios have been tested in order to correlate the enhancement in performance to the cooling channel geometry. There is significant consistency between the experimentally measured PV panel surface temperatures and those obtained from the computational model.
author_names: Tareq Abu Hamed

Aiman Alshare

Hossam Elkhalil
title: Passive cooling of building integrated photovoltaics in desert conditions: Experiment and modeling
venue: Energy
year: 2019

abstract: Abstract Free cooling technique using Phase Change Material (PCM) is a promising process to shave the peak load for the cooling system and reduce energy ventilation consumption. However it needs additional energy for the fan. In the way optimize the process we then proposed a first approach to estimate a priori the flow rate required to reach full freezing or thawing of PCM which is a useful indication of the process efficiency. The approach is based on the inverse method associated with sensitivity coefficient. The objective function was defined in terms of air temperature at the exit of the heat exchanger. The model was compared to experimental data, and the validation of numerical results shows the robustness and the consistency of this method. In the worst case, relative error does not exceed 5 x 10 03.
author_names: A Ousegui

Bernard Marcos

Michel Havet
title: Inverse method to estimate air flow rate during free cooling using PCM air heat exchanger
year: 2019

abstract: Abstract As a southeast neighbor of the heavily industrialized and urbanized region of the Pearl River Delta (PRD) Hong Kong, China, has been susceptible to aerosols transported from the PRD in winter when the prevailing flow is from the west. The decadal trend in pollution during recent decades has likely indicated a difference in aerosol loading between winter and summer when different winds dominate. The surface air temperature shows a wintertime cooling trend during recent decades in Hong Kong, particularly during the midday hours. Differently, the surface air temperature shows a summertime warming trend during recent decades in Hong Kong. By examining the distinct winter versus summer trends in midday hour temperature under low cloud cover conditions in Hong Kong from 1979 to 2014, we found a close relationship between the temperature reduction during midday hours and increased aerosol loading in winter but not in summer. The consistency in turning point for both the increase in aerosol loading and the variation in winter summer temperature differences in the late 1980s also supports the strong association between aerosol and temperature changes. Further analysis shows that there was a significant negative correlation between downwelling solar radiation (DSR) and aerosol loading. Quantitatively, aerosols over Hong Kong during the study period reduced surface DSR and midday temperatures by approximately 30 W m 2 and 2.1 degC for low cloud cover cases.
author_names: Xianyou Yang

Chuanfeng Zhao

Lijing Zhou

Zhangqing Li

Maureen Cribb

Su Yang
title: Wintertime cooling and a potential connection with transported aerosols in Hong Kong during recent decades
year: 2018

abstract: The target of this paper is to develop an enhanced flow thermo structural (FTS) model with high computational accuracy, to perform the integrated analysis of film cooling nozzle guide vane (NGV) An efficient turbulence model and weak spring approach are utilized in the enhanced FTS model. In respect of the power balance principle of aeroengine rotor shaft and temperature test of a typical combustor, the mean temperature inlet and five normalization temperature curves were confirmed, respectively. The temperature sensitive paint (TSP) technology was used to verify the numerical simulation. From this study, we find that the predicted temperature caters for the TSP test well, between which the maximum error is less than 6% and the maximum thermal stress is 758 MPa around the hole edges and the location of stress concentration keeps the consistency with that of the cracks. The maximum thermal stress increases by 10% with the increasing inlet temperature and reduces by about 16% with the shifting of flame peak from the outer to inner hub. The prediction provides general information on the initiation of cracks on a vane segment. The developed enhanced FTS model is validated to be workable and precise in the integrated analysis of film cooling NGV. The efforts of this study provide an integrated analysis approach of film cooling NGV and are promising to provide guidance for the integrated design of film cooling components besides NGV.
author_names: Pengtao Guan

Yan-ting Ai

Chengwei Fei
title: An Enhanced Flow Thermo Structural Modeling and Validation for the Integrated Analysis of a Film Cooling Nozzle Guide Vane
venue: Energies
year: 2019

abstract: West Africa Shea butter is a solid fat at room temperature, with a melting point of 34 38oC. The hardness of Shea butter has limited its application as body cream/lotion due to difficult rubbing ability. The aim of this study is to apply tempering techniques in view of producing a softer butter without altering its chemical composition (fatty acids and unsaponifiables) Tempering temperature, tempering time, cooling rate and stirring rate were varied to determine their effect on the slip melting point, consistency and viscosity of the Shea butter. Results indicated that tempering temperature of 25 30oC with stirring and fast cooling for 6 hours and above produced a softer butter with lower melting point compared to control. KEYWORDS: Shea butter, Tempering, Rheological property, Hardness
author_names: Nurah Tijani Oseni

Julius U Iyasele

O E Uwadia
title: Effect of Tempering, Cooling and Stirring on the Rheological Properties of Shea butter
year: 2019

abstract: The hot spot factor <italic>H</italic> is a crucial component of the thermal diagram in IEC 60076 2 to derive the hot spot temperature from the test data. In this paper, <italic>H</italic> is expressed as the sum of two separable components, one relating to convection in the fluid domain and the other relating to conduction in the solid domain. Dimensional analyses on fluid flow and heat transfer show that both components are functions of dimensionless winding geometry, loss distribution, Re and Pr. The relationship between <italic>H</italic> and Re and Pr for a fixed winding geometry with uniform loss distribution is obtained by conducting computational fluid dynamics (CFD) parametric sweeps and multilayer least square based correlation. The correlation obtained is verified by the consistency between <italic> H</italic> from new CFD simulations and those from the correlation. For nonuniform loss distribution, when the hotspot is at the location of the highest power loss, <italic>H</italic> is in a linear relationship with <italic>Q</italic> and this linear relationship is coupled with a nonlinear relationship between <italic>H</italic> and Re and Pr.
author_names: Xiang Zhang

Zhongdong Wang

Qiang Liu
title: Interpretation of Hot Spot Factor for Transformers in OD Cooling Modes
venue: IEEE Transactions on Power Delivery
year: 2018

abstract: Three kinds of magnetorheological(MR) grease based on different cooling profile was prepared with a magnetic particle and lithium soap weight fraction of 30% and 7%,respectively.The physicochemical property,microstructure and rheological properties of them were investigated.The results show that the property and microstructure of MR grease can be altered to a large extent by the cooling process.When the cooling velocity was faster,the storage modulus and the consistency of the MR grease will become lower,and the separation oil with pressure is worse.The static magnetism of MR grease is almost independent of the cooling profile,but the MR effect of MR grease is dramatically affect by the different cooling velocity,the MR grease prepared by room temperature water bath has the best MR effect than others.The difference in modulus of three MR greases can be attributed to the microstructure variance causing by the different cooling profile.
author_names: Hu Zhi-d
title: The effect of cooling profile on the microstructure and rheology of mineral oil based magnetorheological grease
year: 2014

abstract: Geothermal heating and cooling systems are sustainable methods of temperature control utilizing renewable energy. These systems leverage the subsurface temperatures of the Earth by transferring heat between a fluid and its surroundings underground. This transfer of energy provides heating during colder months, and cooling during the hotter times of the year due to the consistency of the temperature below the Earth's surface year round. Implementing a Geothermal heating and cooling system can save a significant amount of money annually in the form of decreased heating and cooling costs for both residential and industrial applications. Geothermal systems are versatile in the ways that they can be used, for not only residential buildings, but also large commercial buildings. The Massachusetts General Hospital (MGH) located in Boston, MA, is known as one of the top hospitals in the country and therefore utilize a significant amount of energy for heating and cooling. This provides an excellent opportunity for a Geothermal heat pump to be implemented at the MGH. This paper explains how installing a Geothermal vertical closed loop system at the Gray Building of the MGH can significantly reduce costs on heating and cooling. Currently, 37% of the total yearly energy consumption by the MGH is used for heating and cooling of the facility. By implementing the plan outlined in this paper, the MGH facility would see up to 60% savings in heating and cooling costs annually, resulting in a savings of $1,218,626 per year.
author_names: Zoe Zyvith

Mark Thomas Trevena

Ryan Lamantia

Lana Sharp

Andrew K Yong

Sasan Haghani
title: Apr 6 Geothermal Heating Cooling in Massachusetts General Hospital
year: 2018