A physics-based model for frost buildup under turbulent flow using direct numerical simulations

We present a new model for frost buildup under turbulent (and laminar) flow using direct numerical simulations. The physical model consists of two layers, the air and the frost. The air layer is fully resolved and consists of solving for the velocity, temperature, and vapor mass fraction fields. The frost layer thickness is resolved using conservation of mass and energy. Both phases are dynamically coupled using the immersed boundary method. Three-dimensional simulations are conducted in an open-channel configuration. A number of challenges need to be overcome to make these simulations feasible. First, to enforce far-field conditions of zero gradient and prescribed mean temperature and humidity, a source term is added to the energy and transport equations in the flow solver. Second, the mean frost thickness is subtracted after each time step to ensure a constant mean flow thickness and level of turbulence in the numerical domain. Third, a slow-time acceleration approach, which accelerates the frost buildup by a predetermined factor, is employed to bridge the gap between the fast turbulent and slow frost buildup time scales. Finally, a frost densification scheme is used to overcome the difficulties of vertically varying frost properties. The model is validated by comparing the frost thickness and frost thickness buildup rate over a period of one hour from a cooled flat plate experiment. Both quantities compare favorably with experiments

Numerical and experimental verification of a theoretical model of ripple formation in ice growth under supercooled water film flow

Little is known about morphological instability of a solidification front during the crystal growth of a thin film of flowing supercooled liquid with a free surface: for example, the ring-like ripples on the surface of icicles. The length scale of the ripples is nearly 1 cm. Two theoretical models for the ripple formation mechanism have been proposed. However, these models lead to quite different results because of differences in the boundary conditions at the solid-liquid interface and liquid-air surface. The validity of the assumption used in the two models is numerically investigated and some of the theoretical predictions are compared with experiments.Comment: 30 pages, 9 figure

Acute Lithium Intoxication and Factors Contributing to its Morbidity: a 10-Year Review

Background: Lithium has been commonly used for the treatment of several mood disorders particularly bipolar disorder in the last 60 years. This study aimed to analyze patients with lithium intoxication referred to Loghman- Hakim teaching hospital.Methods: This is a cross sectional study that has been done on 108 patients with lithium intoxication during 2001 to 2010. Necessary data were collected by checklists and then analyzed by statistical methods in SPSS version 20.Results: 39.8% of patients were male and most of them were in age group 20-40 years (47.2%). The rate of lithium use in 66.7% of patients was lower than 20 grams and the level of lithium in blood was 1 mEq/lit in 44.4% of patients. The rate of recovery has been significantly relation with BUN, creatinin, Intubation, pCO2 and pH. There was a significant relation between hospitalized with pH, pCO2, Na, absorbent materials, intubation and bicarbonate.Conclusion: Results showed that we should note to the rate and time of lithium used and also severity of signs in management and treatment of patients with the lithium toxicity

Antioxidant activity of extract from a brown alga, Sargassum boveanum

Water and ethanol extracts (WE and EE) from the dried sample of brown alga (Sargassum boveanum) were prepared and examined for its phenolic compounds. Amount of total phenolic compounds in WEwas about 17 ± 0.492 mg catechin equivalent (CE)/g of dry sample, using Folin-Ciocalteu method. The antioxidant activity (AOA) of WE was high at about 90% inhibition of peroxidation of linoleic acid with 7mg dry sample/ml solvent. The IC50 of the WE sample and catechin which was used as the positive control with the hemoglobin catalyzed linoleic acid peroxidation method, were (mg/ml): 3.82 and 0.0713, respectively. The IC50 of the WE sample in terms of CE was 18.76 mg CE/g dry sample.The WE sample exhibited noticeable scavenging effects in DPPH free radical scavenging assay. The radical scavenging activity (RSA) was about 94% at 3 mg dry sample/ml solvent. The phenolic constituent appears to be responsible at least in part, for the observed AOA of the algal extract. The results suggest that this alga could be a potential source of natural antioxidant