2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application最新文献

Numerical Study of Forced Convection Flow Around Rectangular Cylinders with Different Aspect Ratios 不同长径比矩形圆柱绕流强迫对流的数值研究

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363445

A. Joda, I. Cuesta, A. Vernet

{"title":"Numerical Study of Forced Convection Flow Around Rectangular Cylinders with Different Aspect Ratios","authors":"A. Joda, I. Cuesta, A. Vernet","doi":"10.1109/THETA.2007.363445","DOIUrl":"https://doi.org/10.1109/THETA.2007.363445","url":null,"abstract":"The unsteady two-dimensional forced convection heat transfer and fluid flow around rectangular cylinders are investigated numerically. A range of Reynolds number between 100 to 200 and aspect ratios (H/D) 1, 2 and 3 are considered. In the present work, a fractional step finite volume code with staggered variables arrangement is used to solve Navier-Stokes and energy equations. A second order central differencing scheme is applied for both diffusion and convection terms. Time advancement is discretized using a second order implicit Cranck-Nicolson scheme. At the outlet of the domain the convective boundary condition is applied for the velocities and the temperature. The computed results of drag and lift coefficients, Strouhal number, mean recirculation length and Nusselt numbers of the square cylinder are found to be in good agreement with previous numerical results. Correlations between the cylinder Nusselt number and Reynolds number are presented for H/D= 2 and 3. In addition, a correlation of heat transfer is proposed as a function of Reynolds number and the aspect ratio (H/D)","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124938923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 14

Convective Heat Transfer From a Stacked Electronic Package 堆叠电子封装的对流传热

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363420

V. Natarajan

引用次数: 4

Fast Identification Method of the Heat Transfer Coefficient 传热系数的快速识别方法

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363408

P. Bárta

引用次数: 0

The Effects of Surface Roughness on Heat Transfer between Two Contacting Particles 表面粗糙度对两个接触粒子之间传热的影响

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363435

K. Kuwagi, M. Arif, T. Takami

{"title":"The Effects of Surface Roughness on Heat Transfer between Two Contacting Particles","authors":"K. Kuwagi, M. Arif, T. Takami","doi":"10.1109/THETA.2007.363435","DOIUrl":"https://doi.org/10.1109/THETA.2007.363435","url":null,"abstract":"An investigation was carried out to draw a similarity between contact heat transfer and current for two contacting spherical particles where the results can be used for the discrete element method (DEM) simulation. The experimental work is presented in two conditions of mechanical contact phenomena i.e., static contact and dynamic contact, respectively. Nevertheless, for dynamical contact, it is hard to obtain heat transfer directly during the collision. Hence, the authors attempted to use current according to the analogy between heat transfer and current. This paper firstly examined the contact phenomena under the static contact condition. The analysis was based on the contact forces on the particles as well as the surface roughness parameters of the particles. It is found that contact heat transfer and current which flow through a spherical surface have a good similarity in the way they were affected by the surface roughness of the particles. Both contact heat transfer and current increase as surface roughness becomes large. However, this is not a common trend because larger surface roughness yields larger contact resistance. Using the similarity, a simple relation between contact heat transfer and current on two contacting particles (spheres) was introduced. This empirical relation can be used to estimate the heat transfer in dynamic contact condition","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131523758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Fouling Control and Energy Conservation 污垢控制与节能

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363440

T.Reg. Bott

{"title":"Fouling Control and Energy Conservation","authors":"T.Reg. Bott","doi":"10.1109/THETA.2007.363440","DOIUrl":"https://doi.org/10.1109/THETA.2007.363440","url":null,"abstract":"The transfer of heat between two flowing fluids is often accompanied by fouling of the surface that separates them. These deposits represent an insulating layer that restricts the flow of heat between the fluids and therefore results in a loss of heat energy recovery. Furthermore the accumulation of these unwanted deposits can restrict the flow of fluid and hence increase the demand for transport energy. Attention therefore, has to be paid to the possibility that the energy efficiency of any process involving heat transfer, may be jeopardised by the presence of these deposits on heat exchanger surfaces. The paper outlines the mechanisms by which heat transfer surfaces become fouled and the influence of the process variables. It is usually not possible to eliminate the incidence of surface fouling so that it has to be allowed for in the design of the equipment. In addition it is likely that some control measures will have to be introduced in order to maintain heat transfer efficiency and to conserve energy. Methods of control are discussed that involve the use of chemical additives and physical technologies. A combination of chemical and physical techniques for fouling control can be very effective. The discussion in the paper is illustrated with practical data, with particular reference to cooling water","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"165 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114014278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

An Experimental Investigation of Free Cooling by Natural Convection of Vertical Surfaces for Building Integrated Photovoltaic (BIPV) Applications 建筑集成光伏(BIPV)垂直表面自然对流自然冷却的实验研究

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363422

C. Ménézo, M. Fossa, E. Leonardi

{"title":"An Experimental Investigation of Free Cooling by Natural Convection of Vertical Surfaces for Building Integrated Photovoltaic (BIPV) Applications","authors":"C. Ménézo, M. Fossa, E. Leonardi","doi":"10.1109/THETA.2007.363422","DOIUrl":"https://doi.org/10.1109/THETA.2007.363422","url":null,"abstract":"An experimental study is carried out to investigate the effect of the geometrical configuration on the thermal performance of a series of vertical heaters cooled by natural convection of air. The aim of the work is to investigate the physical mechanisms which influences the thermal behaviour of a double-skin photovoltaic (PV) facade. This results in a better understanding of the related phenomena and infers useful engineering information for controlling the energy transfers to the building where the PV system is applied. In real applications, the PV integrated double facade allows local production of electricity and heat to be employed for the building needs. Furthermore increasing the heat transfer rate from the PV surfaces increases the conversion efficiency of the PV modules since they operate better as the working temperature is lower. The test section consists in a double vertical wall, 2 m high, and each wall is constituted by 10 different heating modules 0.2 m high. The separating distance between the walls is varied from 0.03 to 0.16 m, and the convective heat flux at the wall ranges from 75 to 200 W/m. In this study, the heated section is 1.6 m in height. Different heating configurations are analysed, including the uniform heating mode and two different configurations of non uniform, alternate heating. The experimental procedure allows the wall temperature and local heat transfer coefficient to be inferred and shows that the proper selection of the separating distance and heating mode can noticeably decrease the surface temperatures and hence enhance the conversion efficiency of PV modules","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117321213","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 11

Thermo-Mechanical Model of Ball Screw With Non-Steady Heat Sources 非稳态热源下滚珠丝杠的热-力学模型

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363424

Ján, O. Horejš

{"title":"Thermo-Mechanical Model of Ball Screw With Non-Steady Heat Sources","authors":"Ján, O. Horejš","doi":"10.1109/THETA.2007.363424","DOIUrl":"https://doi.org/10.1109/THETA.2007.363424","url":null,"abstract":"A ball screw system is widely used for rapid translating precise motion because of its high efficiency and long lifetime. However, a high-speed ball screw drive system naturally produces heat through friction at contact areas, which thereby causes thermal expansion, which adversely affects machining accuracy. In order to achieve high accuracy and great stiffness, the ball screw preload is common solution of removing the backlash of the ball screw. Consequently the applied preload on screw shaft produces more heat through friction. It results in temperature rise and thermal deformation in the ball screw drive system. Thus a thermally induced preload problem is introduced $the heat source in the bearing becomes non-steady because of the coupling between the generated friction heat and the axial force of screw shaft changed by thermal deformation. A closed loop finite element analysis of ball screw drive system was carried out taking the non-steady heat sources in bearings into account. The developed numerical model confirms significant influence of bearings preload upon thermal stabilization of the ball screw drive system. The results of simulation are in accordance with measured data. The slight discrepancies are probably caused by fact that the heat flux from heated nut is not included in the model during idle time. Further the uniform heat transfer coefficient along the ball screw is applied to the FEA which is not fully in accordance with measurement conditions. Nevertheless, the numerical model sufficiently simulates thermo-mechanical behaviour of ball screw, so it is suitable for estimation of bearing thermal stability","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125627042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 42

LES study of the influence of the vortex generators on cooling of surface-mounted cubes 涡发生器对表面安装立方体冷却影响的LES研究

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363410

H. Hemida, S. Krajnović

{"title":"LES study of the influence of the vortex generators on cooling of surface-mounted cubes","authors":"H. Hemida, S. Krajnović","doi":"10.1109/THETA.2007.363410","DOIUrl":"https://doi.org/10.1109/THETA.2007.363410","url":null,"abstract":"The influence of vortex generators on the enhancement of heat transfer from a wall-mounted cube matrix was investigated by numerical simulation using finite-volume method. The momentum and convective heat transfer equations were discretized and solved using large-eddy simulation. The numerical simulation was performed on a fully developed turbulent flow over one cube mounted in the middle of a cube matrix. Constant heat flux was generated from the cubes. Periodic boundary conditions were applied in both the streamwise and the spanwise directions. In order to study the influence of vortex generator on the flow structures and heat transfer coefficient, the flow and the convective heat transfer equations were solved around two cube configurations: a smooth cube and a cube with vortex generator attached to its surface. The vortex generator used in this investigation is a simple rib attached to the top and the side walls of the cube close to the streamwise edge. The flow Reynolds number based on the bulk velocity and the height of the channel was 13000. Standard Smagorinsky subgrid-scale model was used to model the unresolved scales and heat fluxes. The LES results were compared with the experimental results and good agreement was obtained. Numerical flow visualization was used to provide a better insight into the flow structures and heat transfer coefficient around the cubes. The LES results showed that the flow in the boundary layer around the cube with vortex generator is more turbulent and unsteady than the flow around the smooth cube without the vortex generator. More turbulent structures are generated close to the surface of the cube resulting in a good mixing of heat and hence high heat transfer coefficient","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130341402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Steady-State Behaviour of a Three-Dimensional Pool-Boiling Problem 三维池沸腾问题的稳态行为

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363430

M. Speetjens

{"title":"Steady-State Behaviour of a Three-Dimensional Pool-Boiling Problem","authors":"M. Speetjens","doi":"10.1109/THETA.2007.363430","DOIUrl":"https://doi.org/10.1109/THETA.2007.363430","url":null,"abstract":"Pool boiling serves as physical model problem for electronics cooling by means of phase-change heat transfer. Key for optimal and reliable cooling capacity is better understanding of the conditions that determine the critical heat flux (CHF). Exceeding CHF results in transition from efficient nucleate boiling to inefficient film boiling. This transition is intimately related to the formation and stability of multiple (steady) states on the interface. To this end the steady-state behaviour of a three dimensional pool-boiling problem has been studied in terms of a representative mathematical model problem. This model problem involves only the temperature field within the heater and models the heat exchange with the boiling medium via a nonlinear boundary condition imposed on the fluid-heater interface. The steady-state behaviour is investigated via a bifurcation analysis with a continuation algorithm based upon treatment of the model with the method of separation of variables and a Fourier-collocation method. This revealed that steady-state solutions with homogeneous interface temperatures may undergo bifurcations that result in multiple solutions with essentially heterogeneous interface temperatures. These heterogeneous states phenomenologically correspond with vapour patches ('dry spots') on the interface that characterize transition conditions. The findings on the model problem are consistent with laboratory experiments","PeriodicalId":346940,"journal":{"name":"2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133714781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the Validity of the Boussinesq Approximation in a Developing Mixed Convection Boundary Layer 发展中的混合对流边界层中Boussinesq近似的有效性

2007 International Conference on Thermal Issues in Emerging Technologies: Theory and Application Pub Date : 2007-05-21 DOI: 10.1109/THETA.2007.363439

D. G. Barhaghi, Lars Davidson

引用次数: 8