Brian J. Savilonis

Modeling fire behavior in an enclosure with a ceiling vent

Abstract The flow initiated by a heat source inside an enclosure with a ceiling vent is considered. The problem is formulated computationally in primitive variables and includes compressibility and buoyancy effects; combustion and radiation are ignored. Predictions are obtained by using a field model in a space of 0·45 m × 0·45 m divided into 40 × 40 uniform grids; an additional 8 × 4 grids are employed to represent the vent. A mixing ratio λ (defined mathematically as T mix =λ × ambient temperature + (1 − λ) × vent discharge temperature) is introduced to compute the temperature of the incoming stream at the vent. For λ between 0·3 and 0·5, the mean flow field and interior temperatures show satisfactory comparisons with experimental data. However, the predicted vent temperatures exhibit large fluctuations, which bound the experimental values; the discrepancies may be attributed to the slow frequency response of the thermocouples and numerical oscillations. The results generally show that, for this configuration, the flow field is bistable and vortical inside the enclosure, with an irregular pulsating vent discharge of the order of 0·5 Hz; the interior temperature distribution is essentially uniform.

Variation of arterial compliance within the cardiac pressure pulse

Past investigations of in vivo arterial behavior have concentrated on determining material properties based upon the maximum and minimum pressure and diameter measured over a pulse cycle. A new in vivo technique, based upon continuous measurement of pressure and flow, has been developed to study arterial compliance throughout the pulse cycle. Compliance in the abdominal aorta of rats showed different behavior during the rising and falling portion of the pressure pulse. Previous investigations of canine arteries which used different methods are consistent with these findings. This study demonstrates the utility of a new measurement technique and shows some trends in compliance within the pulse cycle which have neither been revealed by static tests nor by dynamic tests which focused on pulse averaged values.

Survey and evaluation of existing smoke movement models

This paper provides an independent evaluation of a variety of models which have potential use in describing the movement of smoke. Comparison of model results with experimental data from two fires yielded mixed success. Because of the nature of the models, focus is placed on the temperature and the depth of the upper hot gas layer as a function of time.

Spherical Tanks for Use in Thermal Energy Storage Systems

Thermal energy storage (TES) is a vital component of concentrated solar power (CSP). TES makes up for intermittent solar radiation, bad weather, and peak power demand. Currently, a sensible heat storage system using two tanks containing molten salt is considered the most practical and economical TES. Yet further system development is needed in order to improve its performance and economics.In this study of molten salt storage tanks, spherical tanks were investigated as an alternative to cylindrical tanks. Structural and thermal aspects of cylindrical tanks with varying H/D ratios (0.25–5) and spherical tanks of the same volume were compared.Comparison showed that utilization of spherical instead of cylindrical tanks resulted in significant savings in shell building material (28–47%). Heat transfer from the spherical tank’s shell is at least 35% less than cylindrical tanks. Reduction in building material, foundation, and insulation cost can lead to significant cost savings.Copyright

Thermal Stratification in Spherical Tanks

Spherical tanks have the potential for cost reduction in sensible thermal energy storage (TES) systems, by using less tank building material and insulation.The current CFD study compares the Thermal Efficiency (TE) of a thermocline storage system in a spherical tank to a cylindrical tank of the same volume. A parametric study is then performed on a spherical tank during the discharge process to determine the flow parameters that govern the thermocline formation and entrainment. The following parameters are used: tank diameter to inlet diameter ratio D/d = 10, inlet velocity (0.02–0.1 m/s), and ΔT (10–70° C), leading to an inlet Froude number (0.4–3), inlet Reynolds number (500–7500), and tank Richardson number (2–100).The results show a significant correlation between the inlet Reynolds and inlet Froude numbers, and the tank TE, in addition to a weak correlation between the tank Richardson number, based on the tank diameter, and the tank TE. The parametric study also shows a maximum tank TE at a Froude number equal to 0.5, and a proportional decrease of TE as the Reynolds number increases.Copyright

CFD Comparison of Steady and Unsteady Flow Through a Human Nasal Passage

Understanding of the transnasal pressure and flow behavior during normal breathing conditions has been a subject of much discussion and research. In particular we are interested in testing the hypothesis of quasi-steady flow as well as the role of turbulence on nasal flow dynamics.Copyright