Effect of Multiphase Radiation on Coal Combustion in a Pulverized Coal jet Flame

The accurate modeling of coal combustion requires detailed radiative heat transfer models for both gaseous combustion products and solid coal particles. A multiphase Monte Carlo ray tracing (MCRT) radiation solver is developed in this work to simulate a laboratory-scale pulverized coal flame. The MCRT solver considers radiative interactions between coal particles and three major combustion products (CO2, H2O, and CO). A line-by-line spectral database for the gas phase and a size-dependent nongray correlation for the solid phase are employed to account for the nongray effects. The flame structure is significantly altered by considering nongray radiation and the lift-off height of the flame increases by approximately 35%, compared to the simulation without radiation. Radiation is also found to affect the evolution of coal particles considerably as it takes over as the dominant mode of heat transfer for medium-to-large coal particles downstream of the flame. To investigate the respective effects of spectral models for the gas and solid phases, a Planck-mean-based gray gas model and a size-independent gray particle model are applied in a frozen-field analysis of a steady-state snapshot of the flame. The gray gas approximation considerably underestimates the radiative source terms for both the gas phase and the solid phase. The gray coal approximation also leads to under-prediction of the particle emission and absorption. However, the level of under-prediction is not as significant as that resulting from the employment of the gray gas model. Finally, the effect of the spectral property of ash on radiation is also investigated and found to be insignificant for the present target flame

A model of flame propagation in rich mixtures of coal dust in air

A two-phase combustion model describing fundamental coal dust flame propagation phenomena is developed to treat general fuel rich mixtures. The model includes heterogeneous combustion, pyrolysis of the coal, and homogeneous combustion of volatile matter and the optically thick limit for radiative heat transfer. Calculations for coal (fuel) rich mixtures in air were done for equivalence ratios of 3-8. Predicted burning velocities for 50 [mu]m particles of coal with 36% volatile matter indicated a broad maximum of 37 cm/s at an equivalence ratio of 4 (0.367 kg/m3). The minimum computed velocity was 9 cm/s at [phi] = 8 (0.733 kg/m3). The burning velocity was found to increase as the particle size decreased. The chemical kinetics model was highly simplified, but based on experimental information. The predicted flame temperatures and structures compare well with recent experimental data published by the authors. The structure of the flames was found to be strongly influenced by radiative heat transfer. Flame thicknesses were predicted to exceed 10 cm for most conditions studied.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25749/1/0000309.pd

Risk of symptomatic venous thromboembolism following emergency appendicectomy in adults

BACKGROUND: Appendicectomy is the commonest intra-abdominal emergency surgical procedure, and little is known regarding the magnitude and timing of the risk of venous thromboembolism (VTE) after surgery. This study aimed to determine absolute and relative rates of symptomatic VTE following emergency appendicectomy. METHODS: A cohort study was undertaken using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data of patients who had undergone emergency appendicectomy from 2001 to 2011. Crude rates and adjusted incidence rate ratios (IRRs) for VTE were calculated using Poisson regression, compared with baseline risk in the year before appendicectomy. RESULTS: A total of 13 441 patients were identified, of whom 56 (0.4 per cent) had a VTE in the first year after surgery. The absolute rate of VTE was highest during the in-hospital period, with a rate of 91.29 per 1000 person-years, which was greatest in those with a length of stay of 7 days or more (267.12 per 1000 person-years). This risk remained high after discharge, with a 19.1- and 6.6-fold increased risk of VTE in the first and second months respectively after discharge, compared with the year before appendicectomy (adjusted IRR: month 1, 19.09 (95 per cent c.i. 9.56 to 38.12); month 2, 6.56 (2.62 to 16.44)). CONCLUSION: The risk of symptomatic VTE following appendicectomy is relatively high during the in-hospital admission and remains increased after discharge. Trials of extended thromboprophylaxis are warranted in patients at particularly high risk

From Marks of Conformity to Acts of Transgression: An Artistic M.F.A. Thesis of Autobiographical Reenactments for the Camera

This M.F.A. thesis text discusses photographic images that explore the relationship between past and present identities, emotions stemming from social conformity, and the process of autobiographical historical reenactment. The paper reveals how self examination through artmaking provides an entryway into the depiction of social psychology, feminism, reenactment, costuming the self, and memory. Overall, this paper examines the ways in which documented reenactment of one’s past visualizes the relationship between past and present identities.Master of Fine Arts (MFA)Art and DesignUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/41239/2/Buckius_thesis.pd