Heat Transfer: Volume 5最新文献

{"title":"Large Eddy Simulation of Naturally Induced Fire Whirls in a Vertical Square Channel With Corner Gaps","authors":"B. Farouk, K. McGrattan","doi":"10.1115/imece2000-1562","DOIUrl":"https://doi.org/10.1115/imece2000-1562","url":null,"abstract":"\u0000 Naturally occurring fire whirls are rare but highly destructive phenomena. These are mostly generated by the interaction between a buoyant fire plume and its surroundings. The whirling motion generated can enhance the plume length and sustain burning. In this paper, we report the results of a numerical investigation of whirling fires generated in vertical square channels with symmetric corner gaps. The numerical investigations of swirling fire plumes are used to analyze how the corner gaps alters the plume dynamics and combustion. An approximate (low Mach number) form of the Navier-Stokes equations is solved to calculate the mixing and transport of combustion products. Large scale eddies are directly simulated and sub-grid scale motion is represented with a Smagorinsky model. The current approach is based on a fixed heat release rate, regardless of the strength of the whirl generated by the corner slots. The effect of corner slot widths and their configuration on the swirling motion are studied systematically for a given channel geometry and fixed fuel-loss rate.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125936764","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}

{"title":"Modeling a Catalytic Combustor for a Steam Reformer in a Methanol Fuel Cell Vehicle","authors":"M. Sundaresan, S. Ramaswamy, R. Moore","doi":"10.1115/imece2000-1564","DOIUrl":"https://doi.org/10.1115/imece2000-1564","url":null,"abstract":"\u0000 Using a fuel other than pure hydrogen in a fuel cell vehicle (FCV) employing a Proton Exchange Membrane (PEM) fuel cell stack typically requires an on-board fuel processor to provide hydrogen-rich fuel to the stack. In the case of methanol as the source fuel, the reformation process typically occurs in a fuel processor that combines a steam reformer plus a catalytic burner (to provide the necessary energy for the endothermic steam reforming reactions to occur). This paper will discuss a model for the catalytic burner in a methanol fuel processor for an Indirect Methanol FCV. The model uses MATLAB/Simulink software and the simulation provides results for both energy efficiency and pollutant formation.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126674612","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}

{"title":"Modeling Non-Equilibrium CO Oxidation in Combustion Systems","authors":"B. Adams, M. Cremer, David H. Wang","doi":"10.1115/imece2000-1556","DOIUrl":"https://doi.org/10.1115/imece2000-1556","url":null,"abstract":"\u0000 Performance of industrial and utility combustion systems is becoming increasingly affected by limits on pollutant emissions such as NOx and CO. CO emissions impact design and operation of combustion systems, particularly when coupled with NOx reduction technologies that involve lower temperature operation or staged firing. Lower combustion temperatures or delayed mixing of fuel and air helps minimize NOx formation, but can increase CO concentrations and minimize CO oxidation rates. Reacting computational fluid dynamics (CFD) models have been shown to be useful in evaluating and optimizing performance of these new technologies and operating conditions. These CFD models have traditionally used equilibrium chemistry models to predict specie concentrations throughout the combustor, however equilibrium assumptions for CO oxidation at lower temperatures is inaccurate. A non-equilibrium CO model is required to accurately predict the oxidation of CO at temperatures lower than ∼1150 K. This paper reviews the development of a non-equilibrium CO model and integration with a reacting CFD model. The use of the resulting model is illustrated on two combustion systems — a waste gas incinerator and a cyclone-fired utility boiler. Results show that low temperature CO oxidation can be accurately predicted with the use of the non-equilibrium CO model.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128424815","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}

{"title":"Experiments and Numerical Simulations of Flow Patterns of Water Droplets From Fire-Fighting Helicopters","authors":"K. Satoh, K. Sagae, K. Kuwahara, K. T. Yang","doi":"10.1115/imece2000-1560","DOIUrl":"https://doi.org/10.1115/imece2000-1560","url":null,"abstract":"\u0000 In large forest fires over wide areas, aerial fire fighting with water drop from helicopters has been widely employed in the world. After the large earthquake fires in Japan, possibilities were raised to employ similar fire-fighting technique to city fires. However, forest and city fires were inherently different in nature and require different fire-fighting implementations. Since the city fires are concentrated in extent and isolated, thus requiring more dense water application to extinguish fires. As a result, accurate engineering data on the optimum water application relative to a given fire are critically needed to design fire-fighting strategies. This study describes the experiments carried out in open fields using real-life helicopters, in comparison with the 3-D numerical simulations. Numerical simulations can provide reasonable flow patterns of the water droplets from the helicopters, and can be used as a design tool for implementing the fire-fighting technique for real city fires.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128743658","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}

{"title":"A New Method for Estimating the Effects of Thermal Radiation From Fires on Building Occupants","authors":"D. Torvi, G. Hadjisophocleous, Joe Hum","doi":"10.1115/imece2000-1561","DOIUrl":"https://doi.org/10.1115/imece2000-1561","url":null,"abstract":"\u0000 A new model for estimating the effects of high thermal radiation heat fluxes on occupants has been developed. This model allows the user to specify the type of clothing worn by typical occupants (e.g., street clothing or protective clothing), percentage of body covered by clothing, and occupant characteristics (e.g., age). Numerical models of heat transfer in fabrics and skin are used to estimate the times required to produce burn damage to bare and clothed skin. These skin burn estimates are used along with occupant characteristics to estimate the time-dependent probability of death from a fire. This paper reviews existing models for estimating the effects of high heat fluxes on occupants, describes the heat transfer models used to make skin burn estimates, and compares the results of the new model with those from existing models.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126712773","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}

{"title":"Modelling of Convective Melt Flow and Interface Shape in Commercial Bridgman-Stockbarger Growth of CdZnTe","authors":"T. D. Rule, Ben Q. Li, K. Lynn","doi":"10.1115/imece2000-1587","DOIUrl":"https://doi.org/10.1115/imece2000-1587","url":null,"abstract":"\u0000 CdZnTe single crystals for radiation detector and IR substrate applications must be of high quality and controlled purity. The growth of such crystals from a melt is very difficult due to the low thermal conductivity and high latent heat of the material, and the ease with which dislocations, twins and precipitates are introduced during crystal growth. These defects may be related to solute transport phenomena and thermal stresses associated with the solidification process. As a result, production of high quality material requires excellent thermal control during the entire growth process. A comprehensive model is being developed to account for radiation and conduction within the furnace, thermal coupling between the furnace and growth crucible, and finally the thermal stress fields within the growing crystal which result from the thermal conditions imposed on the crucible.\u0000 As part of this effort, the present work examines the heat transfer and fluid flow within the crucible, using thermal boundary conditions obtained from experimental measurements. The 2-D axisymetric numerical model uses the deforming finite element method, with allowance made for melt convection, solidification with latent heat release and conjugate heat transfer between the solid material and the melt. Results are presented for several stages of growth, including a time-history of the solid-liquid interface (1365 K isotherm). The impact of melt convection, thermal end conditions and furnace temperature gradient on the growth interface is evaluated. Future work will extend the present model to include radiation exchange within the furnace, and a transient analysis for studying solute transport and thermal stress.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"66 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114123840","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}

{"title":"Metal Monoxide Diagnostics in Particle Synthesis Flames","authors":"Yijia J. Chen, A. Colibaba-evulet, N. Glumac","doi":"10.1115/imece2000-1552","DOIUrl":"https://doi.org/10.1115/imece2000-1552","url":null,"abstract":"\u0000 Recent measurements of metal monoxides in powder producing flames are reviewed and discussed. While the mole fraction profiles of species such as SiO, AlO, and TiO can in principle be used to infer useful information about metalorganic decomposition in flames, the dominant features of these profiles appear to be due to the partial pressure of the solid product. Most monoxides do serve as good markers of the flame zone, but are no better than emission profiles of key excited intermediates. Monoxide profiles may, however, be of significant value in validating future comprehensive multiphase models of the synthesis process.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"308 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116603157","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}

{"title":"Numerical Modeling of Cylindrically Shaped Propellant Packages for the U.S. Army","authors":"E. Zimmerman","doi":"10.1115/imece2000-1572","DOIUrl":"https://doi.org/10.1115/imece2000-1572","url":null,"abstract":"\u0000 The United States Army is in the process of developing the next generation of 155mm self propelled artillery through the Armament Systems Division of United Defense in Minneapolis, Minnesota. This next generation artillery system, called Crusader, is fully automated and can fire up to 10 rounds a minute at distances in excess of 40 km. The weapon system employs a new Modular Artillery Charge System (MACS). MACS consists of a low zone charge, the M231, and a high zone charge, the XM232. Both are rigid combustible cylinders filled with propellant and they are approximately 15 cm in diameter and length. The XM232 is filled with approximately 500 cylindrically shaped propellant grains. The grains are similar in size and shape to that of a typical foam ear plug issued to visitors to high noise areas. A two centimeter thick center core of the cylinder which runs the length of both charges is filled with granular explosive powder which is used to centrally ignite the charges. Between one and six of the 15 cm diameter cylinders are loaded into the gun barrel depending on the distance to the target.\u0000 It is the goal of this new program to have highly accurate first fire capability for maximum effectiveness on the battlefield. It is imperative to have an accurate prediction of the exit velocity of the artillery projectile at time of firing to achieve this goal. Actual firings of the new gun tube with the XM232 propellant canisters revealed that the exit velocity of the projectile was highly dependent on the temperature of the propellant prior to firing. (The velocity achieved by the M231 is relatively insensitive to temperature.) One avenue under review to provide the propellant temperature prior to firing is to physically measure it. This was easily accomplished in earlier artillery systems as the propellant was granular and stored in cloth sacks. The soldier simply inserted a thermometer through the cloth to obtain a bulk temperature of the propellant inside. The new XM232 does not allow this as the canister walls are impervious and even if a way was found to insert a thermometer into the canister — the obtained temperature would be questionable considering the jumbled nature of the small propellant cylinders inside. Additionally, Crusader’s high rate of fire and automated ammunition handling system does not permit the soldier to manually take the temperature of the charge.\u0000 During August 1998 a series of test firings of the new gun barrel were conducted with the XM232s. Selected XM232s were instrumented with thermocouples located at different locations within the cylinder as shown in figure 1. The MACS were then soaked for 24 hours at either 50C or −30C. The MACS were then placed on wooden racks in a large thermal chamber maintained at 20C. The temperatures of the thermocouples were then recorded over a period of time as they either warmed or cooled. With this transient experimental data in hand a numerical model could be developed to predict the tempe","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121736994","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}

{"title":"A Thermal Model for Reburning Fuel Injectors in Glass Furnaces","authors":"L. Swanson, R. Koppang","doi":"10.1115/imece2000-1555","DOIUrl":"https://doi.org/10.1115/imece2000-1555","url":null,"abstract":"\u0000 A quasi-steady multi-mode heat-transfer model for retraining fuel injectors in glass furnaces has been developed that predicts the effect of geometry, furnace heat source and heat sink temperatures, radial and axial injector wall conduction, and coolant flow rate on the injector wall temperature distribution. The model imposes a radiation boundary condition at the outlet tip of the injector, which acts as a heat source. A parametric study has been conducted to investigate effects that the furnace gas temperature, reburning methane fuel and purge-air flow rates, and furnace wall temperature have on the injector wall temperature distribution. For nominal operating conditions, highly nonlinear temperature distributions were observed throughout the injector. Operation with methane as the coolant produced an extremely large temperature gradient near the injector tip that could cause excessive thermal stresses in the injector wall. The results also showed that nominal injector operating conditions should prevent alkali deposition at the injector tip and produce injector/metallic disconnect temperatures well below the initial deformation temperature for stainless steel.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"105 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114924349","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}

{"title":"Effect of Draw Furnace Geometry on High Speed Optical Fiber Manufacturing","authors":"Xu Cheng, Y. Jaluria","doi":"10.1115/imece2000-1583","DOIUrl":"https://doi.org/10.1115/imece2000-1583","url":null,"abstract":"\u0000 The motivation of manufacturers to pursue higher productivity and low costs in the fabrication of optical fibers requires large diameter silica-based preforms drawn into fiber at very high speed. An optimal design of the draw furnace is particularly desirable to meet the need of high-volume production in the optical fiber industry. This paper investigates optical fiber drawing at high draw speeds in a cylindrincal graphite furnace. A conjugate problem involving the glass and the purge gases is considered. The transport in the two regions is coupled through the boundary conditions at the free glass surface. The zonal method is used to model the radiative heat transfer in the glass. The neck-down profile of the preform at steady state is determined by a force balance, using an iterative numerical scheme. Thermally induced defects are also considered. To emphasize the effects of draw furnace geometry, the diameters of the preform and the fiber are kept fixed at 5 cm and 125 μm, respectively. The length and the diameter of the furnace are changed. For the purposes of comparison, a wide domain of draw speeds, ranging from 5 m/s to 20 m/s, is considered, and the form of the temperature distribution at the furnace surface is kept unchanged. The dependence of the preform/fiber characteristics, such as neckdown profile, velocity distribution and lag, temperature distribution and lag, heat transfer coefficent, defect concentration, and draw tension, on the furnace geometry is determined. Based on these numerical results, an optimal design of the draw furnace can be developed.","PeriodicalId":221080,"journal":{"name":"Heat Transfer: Volume 5","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131375673","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}