Analysis of heat transfer during glass forming

Α thermal model is described which is intended to simulate internal heat transfer in glass being cooled by the mold and plunger after pressing. The heat transfer analysis in glass accounts for the spectral nature of radiation, the dependence of the thermophysical properties of glass on temperature and the contact heat transfer between mold and glass as well as plunger and glass during and after pressing. Heat exchange between glass and mold as well as plunger across a very small gap by contact conduction and thermal radiation are also accounted for. To assess the utility of the Rosseland diffusion approximation for radiative transfer, the results are compared with those based on rigorous formulation of radiative transfer. Numerical solutions have been obtained for typical condidons simulating symmetric and asymmetric cooling as well as cyclic operation, and the results are presented and discussed. During the dwell time thermal contact conduction between the glass and the mold as well as plunger is the dominant heat extraction mechanism from the glass. Results show that radiation from the surface of the glass plays a relatively small part in the heat extraction process, but radiation from the interior of the glass is much more significant but less important than thermal contact conduction

Literature review and experimental investigation of heat pipes

Tests on heat pipes determine operational limits, external boundary conditions, noncondensable gas effects, startup behavior, and geometric configurations. Experiment consists of design, construction, and testing of an apparatus for measuring wick properties, conventional heat pipes and coplanar heat pipes

Comparison of the diffusion approximation and the discrete ordinates method for the investigation of heat transfer in glass

Heat transfer by combined conduction and radiadon has been investigated in a one-dimensional glass layer. The layer is semitransparent to radiadon and the dependence of the absorption coefficient on wavelength is accounted for. The discrete ordinates method and the diffusion approximation are used to analyze radiative transfer. The differencing scheme for the discrete ordinates method has been investigated to obtain the constant total heat flux distribution across the glass layer as required by the energy conservation equation, and the best uniformity is obtained with the diamond scheme. The results predicted by the discrete ordinates method are in good agreement with those based on the exact (integral) equation formulation of radiative transfer. The diffusion approximation greatly underpredicts the temperature and heat flux distributions in the glass layer when the thickness or the opacity of the layer is small. The predictions of the diffusion approximation are only reasonable for thick glass layers. This approximation should be used with extreme caution to obtain quantitatively accurate results

An experimental investigation of natural convection with solidification in a differentially heated cavity

This paper introduces an experimental rig used to produce data for the validation of computational models of natural convection within water in an enclosed cavity. The rig consisted of a rectangular cavity with the two long sides maintained at constant temperature. All other surfaces were insulated and adiabatic except for the top surface which was a free surface with an air gap between the free surface and the insulation. Experimental data in the form of velocity, ice growth rate and profiles are presented at 30 min time steps with a cold wall temperature of −10 °C and hot wall temperature of 5 °C. The data produced has systematic and random errors of ±0.4% and ±0.5%, respectively

Three-dimensional flow and thermal structure in glass melting furnaces : Part II. Effects of batch blanket and bubbles

This paper is the second part of a parametric study of the flow and thermal structures in glass melting furnaces with a throat. The effects of the following parameters are discussed: a) the batch velocity, b) the melting temperature, c) the submerged depth of the batch, d) the wall heat losses, and e) the thickness of glass melt containing gas bubbles under the batch. The study indicates that the partially submerged batch and heat losses through the refractories have a strong impact on both the longitudinal and spanwise flow patterns of the molten glass. These physical phenomena must be accounted for if one wants to realistically simulate the natural convection circulation of the molten glass in the bath

Paskutinysis XIX a. Vilniaus universiteto filosofijos profesorius

Straipsnyje, skirtame filosofo Angelo Daugirdo (1776–1835) 200-osioms gimimo metinėms, apžvelgiami šio filosofo gyvenimo ir kūrybos svarbiausi bruožai. Kitaip nei J. Sniadeckis, A. Daugirdas Apšvietos empirizmą siekė suderinti su škotų sveiko proto filosofija ir katalikiškosios filosofijos kai kuriais elementais. Jis tyrinėjo gnoseologijos, logikos, psichologijos, filosofijos istorijos ir moralės filosofijos problemas. Logikos mokslas apima A. Daugirdo pažinimo teoriją: logikos tikslas yra pateikti metodą, kuriuo remiantis galima atskleisti konkrečias tiesas visose žmogiškojo žinojimo srityse. Svarbiausias proto gebėjimas yra išorinių objektų pažinimas. Žmogaus pojūčiai yra prielaida sąvokoms apie išorines substancijas, kurių jie yra veikiami. Sekdamas J. Locke‘o pirminių ir antrinių kokybių samprata, A. Daugirdas išskyrė santykines ir absoliučias kokybes. Tiesiogiai žmogus gali pažinti tik savo paties vaizdinius ir jų santykius, bet ne išorines substancijas. Pažinimo tikrumas yra tiesioginis, apimantis subjekto vaizdinių ir jų santykių pažinimą, ir tarpiškas, kurį sudaro vaizdinius atitinkančių daiktų pažinimas

Teachers Who Collaborate With a Professional Writing Organization: The Importance of Critical Stance

A wide body of research finds teacher preparation programs fail to address the complexity of writing instruction, especially for secondary English-language Arts teachers (Coker & Lewis, 2008; Graham, 2019; Wahleithner, 2018). Beliefs and knowledge about writing determine how teachers approach pedagogical practices (McCarthey & Mkhize, 2013). One of many contextualized social literacy practices, writing is always ideological (Gee, 2105; Moje & Lewis, 2007). Competing research philosophies complicate development of teachers\u27 practices and impedes research dissemination (Coker & Lewis, 2008; Hillocks, 2008; National Writing Project & Nagin, 2006). Structures informing school-based writing limit the types of writing practices (Bazerman, 2016). Using a phenomenological framework with a focus on sociocultural literacy, the researcher used a semistructured interview protocol with four ELA teachers who collaborated with an out-of-school writing organization, exploring their lived experiences teaching writing. Professionals with the organization structured on outcomes of resiliency, personal fulfillment, community, and engagement (Boston Youth Arts Evaluation Project, 2012), worked with teachers. Research questions were developed using Janks\u27 (2009, 2010) critical literacy framework. An intercoder protocol for reliability ( O\u27Connor & Joffe, 2020) was employed after subjective analysis units were coded (Campbell et al., 2013). Coded text was heuristically analyzed for frequency (Saldaña, 2016) and common lived experiences (Vagle, 2014) teaching writing. Multiple cycles of emergent coding allowed development of themes which aligned with Janks and domains of critical stance (Lewison et al., 2015); all participants displayed these embedded practices. Because qualitative methodology was used, results are not generalizable (Creswell & Creswell, 2018). Teachers shared beliefs about the value of writing as expression and as an important school-based skill. Participants shared attributes of culturally responsive caring (Gay, 2018) and ethics of care (Noddings, 2005); relational practices preceded curricular practices. Implications suggest teacher preparation could directly target preservice ELA teachers who articulate broad understandings of writing with information regarding writing theories and pedagogy. Interventions should involve teacher licensing, defining knowledge required of secondary ELA teachers. Implications also indicate out-of-school writing organizations should be utilized as resources for writing development. The study indicates need for more research regarding how professional writing organizations can expand collaboration with ELA teachers

An experimental and analytical study of real surface effects on radiant heat transfer

Comparison of experimental data with predictions based on simple and more detailed models for radiation properties of surface

HT2003-47190 ASSESSMENT OF THE THERMAL PERFORMANCE OF ALTERNATE FIRING SCHEMES IN OXYGEN-FIRED GLASS MELTING FURNACES

ABSTRACT Three firing schemes for an industrial oxygen-fired glass melting furnace were examined to determine the thermal performance and relative merits of each scheme. A comprehensive computer model was used to investigate the effects of each scheme on the combustion and heat transfer in the furnace. The three-dimensional computer model, suitable for predicting and analyzing fluid flow, combustion and heat transfer has been used to simulate the combustion space of the furnace. The turbulent flow field is obtained by solving the Favre averaged Navier-Stokes equations and using the k-ε model to calculate the turbulent shear stresses and close the equation set. The combustion model consists of a single step, irreversible, infinitely fast reaction. A mixture fraction is used to track the mixing of fuel and oxidant and thus reaction progress in this mixing limited model. An assumed shape PDF method is utilized to account for turbulent fluctuations. Radiative heat transfer in the combustion gases and between surfaces is modeled using the discrete ordinates method coupled with the weighted-sum-of-gray-gases model. The model furnace for all three firing schemes was the same size and shape, was charged from the rear end wall and was pulled from the front wall. The three schemes investigated were: 1) non-interlaced side-wall fired, 2) interlaced side-wall fired, and 3) end fired. The results show that all three arrangements provide similar thermal performance and heat transfer characteristics. However, the flow field for the non-interlaced arrangement is very complex in the region where jets from opposing walls meet at the furnace center line. This type of jet interference can lead to unstable flow, particularly at the centerline of the furnace. Unstable flow conditions can affect the heat transfer characteristics of the furnace and make the furnace difficult to operate. Conversely, the interlaced and end-fired schemes do not exhibit the jet interference seen in the non-interlaced arrangement. While the results indicate that the thermal performance of all three arrangements were similar, the possibility of jet interference suggests that an interlaced or endfired arrangement is preferable

Adaptive use in Boston : a developer's perspective

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1988.Includes bibliographical references.by Julia A. Viskanta.M.S