8,692 research outputs found
Applicability of Phase-Function Normalization Techniques for Radiation Transfer Computation
No full textThe applicability of recently-developed four phase-function (PF) normalization techniques for modeling radiation transfer in strongly anisotropic scattering media is intensively examined using the discrete-ordinate method. The three simple techniques via normalization of only the forward- and/or backward-scattering directions were shown to reduce normalization complexity whilst retaining diffuse radiation computation accuracy for Henyey-Greenstein (HG) PFs. For Legendre PFs, however, such simple techniques are found to result in unphysical negative PF value at one or few correction direction in some cases. Additionally, negative PF values can occur for these simple techniques for ballistic radiation transfer for both HG and Legendre PF types. If negative-intensity correction is applied, however, radiative heat transfer calculation can still converge regardless of the appearance of negative PF values. The relatively complex Hunter and Guo 2012 technique, in which normalization is realized through a correction matrix covering all discrete directions, is shown to be applicable for diffuse and ballistic radiation for both PF types.Peer reviewed
Flow and heat transfer inside a new diversion-type gas heating device
No full textThe present paper characterizes ethylene glycol flow and heat transfer inside a new diversion-type gas heating device. A 2-D natural convection heat transfer model was built and solved by the finite volume method with unstructured body-fitted grids. The numerical model was first validated through temperature comparison with experimental measurements in a conventional device structure. Then analyses and comparisons of the flow fields and temperature distributions with use of different guide plate structures were carried out. The numerical results show that using the guide plate structures can form better organized flow patterns that augment heat transfer. The heat required for heating up the gas passing through the heating device can be reduced by 3% via installing two guide plates.Peer reviewed
Reborn Translated: Xiaolu Guo as a World Author
No full textThis paper introduces the concept of “world author,” taking as its exemplar the Chinese British writer and filmmaker Xiaolu Guo. It investigates how Guo utilizes her bilingualism to construct and negotiate her creative agency, especially when dealing with the political and commercial forces imposed on diasporic authors. Through engaging with Rebecca Walkowitz’s idea of world literature as being “born translated,” I point out that the translational should not be limited to the thematic and representational arrangements internal to a given text. Instead, translation as movements between linguistic systems and media forms can generate multipleversions of a text, to the point that such translational multiplicity fundamentally challenges its supposed singularity. This argument is demonstrated with Guo’s self-translation of the stories of Fenfang and her filmic adaptation of the novel UFO in Her Eyes. Through these examples of what I call “translational rebirths,” I demonstrate the importance of paratextual details and intertextual connections between clusters of an author’s creative output for the interpretation and appreciation of l’oeuvre d’un auteur instead of une oeuvre d’art. This case study also shows the need for the academic debates on world literature to go beyond the singularity of texts and evaluative criteria of worldliness based on this assumption, so that the discipline can realize its full potential in accommodating multilingual transnational authors like Guo
3-D simulation of gases transport under condition of inert gas injection into goaf
No full textTo prevent coal spontaneous combustion in mines, it is paramount to understand O2 gas distribution under condition of inert gas injection into goaf. In this study, the goaf was modeled as a 3-D porous medium based on stress distribution. The variation of O2 distribution influenced by CO2 or N2 injection was simulated based on the multi-component gases transport and the Navier-Stokes equations using Fluent. The numerical results without inert gas injection were compared with field measurements to validate the simulation model. Simulations with inert gas injection show that CO2 gas mainly accumulates at the goaf floor level; however, a notable portion of N2 gas moves upward. The evolution of the spontaneous combustion risky zone with continuous inert gas injection can be classified into three phases: slow inerting phase, rapid accelerating inerting phase, and stable inerting phase. The asphyxia zone with CO2 injection is about 1.25~2.4 times larger than that with N2 injection. The efficacy of preventing and putting out mine fires is strongly related with the inert gas injecting position. Ideal injections are located in the oxidation zone or the transitional zone between oxidation zone and heat dissipation zone.Peer reviewed
Heat Transfer and Thermodynamic Processes in Coal-Bearing Strata Under Spontaneous Combustion Condition
No full textSimulations and experiments have been carried out to investigate heat transfer and thermodynamic processes in coal-bearing strata in order to quantitatively understand the development of underground coal fires under spontaneous combustion condition. With controlled temperature and under lean oxygen conditions, the thermodynamic parameters for coal oxidation at different stages are experimentally determined in combination with simultaneous thermal analysis. A combined heat transfer model of conduction, convection and radiation with finite reactions is developed for the porous coal and rocks. The temperature distributions in the coal and roof strata at different times are simulated based on the single- and two-stage kinetic models, respectively, and compared with field geophysical prospecting. Effects of oxidation kinetic properties due to coal metamorphism on propagation of coal fires are examined. It reveals that a significant step change exists during the thermal process of coal fire caused by two-stage oxidation, and the coal rank of occurrence directly determines the spontaneous combustion period of underground coal fire.Peer reviewe
Spectral investigation of solar energy absorption and light transmittance in a water-filled prismatic glass louver
No full textWater-filled prismatic glass louver was proposed to save energy consumptions in buildings because such innovative louvers can harvest solar energy as well as improve daylighting quality rather than “block” sunlight like traditional louvers. To enable this technology the effectiveness of ultraviolet (UV) and infrared (IR) energy harvest and visible (VIS) light transmittance was investigated via Monte Carlo simulations in this case study. The 7-band spectral model for glass and water was evaluated and adopted for several cases of solar spectra of different air mass (AM) coefficients with both direct and diffuse irradiation. Absorption and transmittance in different band regimes as well as in water and glass respectively were differentiated and compared. Practical solar data in Phoenix, Flagstaff, and Golden were utilized to demonstrate the performance of the proposed louver under different locations and realistic conditions. Results show that the device facing normally to direct sunlight can harvest around 51-54% of the total solar energy and transmit 74-76% VIS for daylighting in the range of AM1 to AM3. In particular for AM1.5, VIS transmittance reaches 76% for both direct and diffuse irradiation; UV absorption achieves 80% and 85% and IR absorption reaches 64% and 82% for diffuse and collimated irradiation, respectively. In all the three places tested, the device absorbs about 81% IR and 87% UV, and transmits about 76% VIS.Peer reviewe
Unsteady simulation for optimal arrangement of dedusting airduct in coal mine heading face
No full textTo optimize dedusting efficiency in coal mines, a model of dust movement in heading roadway with far-pressing-near-absorption ventilation system was built. The empirical drag force model was applied into the unsteady inter phase coupling modeling of air and dust flow. The Discrete Phase Modeling in Fluent was employed to solve the problem and unstructured grids were utilized to mesh the complex 3-D roadway with different airduct allocations. Results show that the dedusting efficiency with the dedusting fan in the air return side is obviously better than that with the fan in the middle of the heading machine. The dedusting efficiency decreases within creasing distance between air inlet and heading section. When this distance is 2.0mwith airduct in the air return side, it has the best dedusting efficiency; in which the dust concentration in the front of roadway after 60 seconds of digging and cutting decreases from 1150mg/m3 to 365mg/m3; the average dust concentration in roadway decreases from 597mg/m3 to 144mg/m3; and the total dedusting efficiency reaches up to 75.88%.Peer reviewe
Monitor in-situ superconducting temperature via optical whispering-gallery mode sensors
No full textMonitor in-situ superconducting temperature via optical whispering-gallery mode sensorsPeer reviewe
High thermal conductance across c-BN/diamond interface
No full textHigh thermal conductivity electronic components with low interfacial thermal resistance are of technological importance and fundamental interest of research. Diamond, a superhard material with ultrahigh thermal conductivity at room temperature, is desirable for microelectronics thermal management. Cubic polymorph of boron nitride (c-BN) is a promising material due to wide bandgap and diamond like structure and properties. To understand the nature in thermal transport of diamond, c-BN and the most commonly used silicon (Si) semiconductor, ab initio phonon Boltzmann transport equations are employed to investigate lattice vibrational properties of these three materials. At 300 K, the predicted thermal conductivity of Si, diamond and c-BN reached 142, 2112, and 736 W/(m·K), respectively. What's more, heat transport phenomena across the interfaces of Si/diamond, c-BN/diamond and Si/c-BN are unfolded. In comparison, the interfacial thermal conductance of c-BN/diamond is ten-fold of Si/diamond; besides, the thermal conductance across Si/c-BN interface is 20.2% larger than that of Si/diamond at 300 K and 18.9% larger at 340 K. These findings provide us new vision and potential solution to heat dissipation of high-local-power density devices, shedding light on future thermal management of c-BN and diamond related electronics.Peer reviewe
A review on heat transfer enhancement with nanofluids
No full textAdvances in technology miniaturization with increasing power density call for new technologies for enhancing heat transfer. Enhancement of heat transfer with use of nanofluids has been a hectic topic of research and development since the term “nanofluid” named in 1995, mainly because the thermophysical properties of nanofluids in most reports in the literature showed supremacy or improvement over their base fluids that may not allow the fulfilment of the present cutting-edge technology needs. Significant progress in this field has been made in the past two decades. This review summarizes a variety of the experimentally-measured thermal properties of common nanofluids, the enhancement mechanisms discovered or hypothesised, the models used for properties and heat transfer characteristics, and the applications of nanofluids for enhancing heat transfer. The model of artificial neutral network is particularly emphasized. Applications to cooling technology, renewable energy and energy systems, and building technology are detailed. Challenges and areas for future research are identified.Peer reviewe
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