• Energy Research
• physical sciences close
• 6. Clean water close
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Riblet and superhydrophobic surfaces are two typical passive control technologies used to save energy. In this study, three microstructured samples—a micro-riblet surface (RS), a superhydrophobic surface (SHS), and a novel composite surface of micro-riblets with superhydrophobicity (RSHS)—were designed to improve the drag reduction rate of water flows. Aspects of the flow fields of microstructured samples, including the average velocity, turbulence intensity, and coherent structures of water flows, were investigated via particle image velocimetry (PIV) technology. A two-point spatial correlation analysis was used to explore the influence of the microstructured surfaces on coherent structures of water flows. Our results showed that the velocity on microstructured surface samples was higher than that on the smooth surface (SS) samples, and the turbulence intensity of water on the microstructured surface samples decreased compared with that on the SS samples. The coherent structures of the water flow on microstructured samples were restricted by length and structural angles. The drag reduction rates of the SHS, RS, and RSHS samples were −8.37 %, −9.67 %, and −17.39 %, respectively. The novel established RSHS demonstrated a superior drag reduction effect and could improve the drag reduction rate of water flows.

The paper considers problems of biosynthesis of higher plants' biomass and "biological incineration" of plant wastes in a working physical model of biological LSS. The plant wastes are "biologically incinerated" in a special heterotrophic block involving Californian worms, mushrooms and straw. The block processes plant wastes (straw, haulms) to produce soil-like substrate (SLS) on which plants (wheat, radish) are grown. Gas exchange in such a system consists of respiratory gas exchange of SLS and photosynthesis and respiration of plants. Specifics of gas exchange dynamics of high plants--SLS complex has been considered. Relationship between such a gas exchange and PAR irradiance and age of plants has been established. Nitrogen and iron were found to the first to limit plants' growth on SLS when process conditions are deranged. The SLS microflora has been found to have different kinds of ammonifying and denitrifying bacteria which is indicative of intensive transformation of nitrogen-containing compounds. The number of physiological groups of microorganisms in SLS was, on the whole, steady. As a result, organic substances--products of exchange of plants and microorganisms were not accumulated in the medium, but mineralized and assimilated by the biocenosis. Experiments showed that the developed model of a man-made ecosystem realized complete utilization of plant wastes and involved them into the intrasystem turnover.

Abstract The subchannel codes such as COBRA-TF (CTF) are often used in the simulation of thermal hydraulic parameters in a reactor core. Use of these codes for safety analysis requires extensive validation against experimental data. While typically validation is performed on experiments in water, a large number of experiments using refrigerant are available in literature and may be used to expand the validation range of these codes. This research is focused on the subchannel code CTF which has been modified to incorporate Refrigerant-134a fluid properties. Subsequently the modified code was tested against several experimental results available for R-134a. Evaluation of the Heat Balance Method (HBM) and Direct Substitution Method (DSM) for CHF was carried out. In the case of the CHF Look-Up Table (LUT), fluid-to-fluid scaling was performed to predict the local CHF phenomena. Overall the HBM predictions show better agreement (with the exception of Katto's correlation when applied to test section with a cold-wall) as compared to the CHF LUT results which tended to significantly overpredict dryout under high qualities.