Solar pond

Shallow pools of liquid to collect low-temperature solar generated thermal energy are described. Narrow elongated trenches, grouped together over a wide area, are lined with a heat-absorbing black liner. The heat-absorbing liquid is kept separate from the thermal energy removing fluid by means such as clear polyethylene material. The covering for the pond may be a fluid or solid. If the covering is a fluid, fire fighting foam, continuously generated, or siloons are used to keep the surface covering clean and insulated. If the thermal energy removing fluid is a gas, a fluid insulation layer contained in a flat polyethlene tubing is used to cover the pond. The side of the tube directed towards the sun is treated to block out ultraviolet radiation and trap in infrared radiation

Characterization of Two-Phase Flow in Microchannels

Aluminum multi-port microchannel tubes are currently utilized in automotive air conditioners for refrigerant condensation. Recent research activities are directed toward developing other air conditioning and refrigeration systems with microchannel condensers and evaporators. Three parameters are necessary to analyze a heat exchanger performance: heat transfer, pressure drop, and void fraction. The purpose of this investigation is the experimental investigation of void fraction and frictional pressure drop in microchannels. A flow visualization analysis is another important goal for two-phase flow behavior understanding and experimental analysis. Experiments were performed with a 6-port and a 14-port microchannel with hydraulic diameters of 1.54 mm and 1.02 mm, respectively. Mass fluxes from 50 to 300 kg/s.m2 (range of most typical automotive applications) are operated, with quality ranging from 0% to 100% for two-phase flow experiments. R410A, R134a, and air-water mixtures are used as primary fluids. The results from the flow visualization studies indicate that several flow configurations may exist in multi-port microchannel tubes at the same time while constant mass flux and quality flow conditions are maintained. Flow mapping of the fluid regimes is accomplished by developing functions that describe the fraction of time or the probability that the fluid exists in an observed flow configuration. Experimental analysis and flow observations suggest that pressure drop and void fraction in microchannel is dependent on the most probable flow regime at which the two-phase mixture is flowing. In general, correlations for void fraction and pressure drop predictions are based in a separated flow model and do not predict the experimental results in the range of conditions investigated. A flow regime based model is developed for pressure drop and void fraction predictions in microchannels.Air Conditioning and Refrigeration Project 10

Interaction Support for Hybrid Groups of Paper and Digital Documents on Tabletops

Based on the results of a user study, this paper presents a set of hybrid interaction techniques for groups of paper and digital documents on interactive surfaces. By leveraging a novel concept of tangible controls, these techniques allow highly flexible, fluid and lightweight interactions

An automated method for determining nitrate-nitrogen in soil extracts

A method is described in which nitrate is determined automatically in 2N KCl extracts of calcareous soil. Nitrate is reduced to nitrite with hydrazine and copper catalyst under alkaline conditions at 37°C. The nitrite formed is reacted with sulphanilamide in acid solution to produce a diazonium salt. This salt is then coupled with N-1-naphthylethylenediamine dihydrochloride to form a soluble coloured compound. The absorbance of the coloured solution is measured at 520 nm. The method has advantages over current published methods in that problems associated with precipitation of calcium and magnesium ions were overcome by buffering the sample stream at a pH level that allowed for the conversion of substantial amounts of nitrate to nitrite but prevented precipitation. In addition, the method has removed the need for a dialyser to overcome interfering cations. The method is precise, accurate, sensitive and rapid. The operating range is 0 to 4 p.p.m. N03-N (solution) with a coefficient of variation of 0·7%

Automated pipeline for the analysis of a scale-reduced steel cable net

This paper proposes a digitally twinned experimental analysis of a scale-reduced laboratory-sized steel cable net subjected to vertical loading. The test is aimed at establishing automated pipelines of information and analysis between the measurements (displacements of nodes) and the numerical model of the cable net, which are seamlessly interconnected through a BIM model. These automated pipelines erect the frame of the development of a digital twin of the cable net with structural analysis purposes. For the sake of measurements, a terrestrial laser scanner is used. Displacements of the nodes are extracted using computational geometry tools. For the sake of analysis, a data-based numerical model is proposed to obtain the tensile state of the cables. Precisely understanding the force distribution along nets is a challenge at design, construction and operation stages. This research belongs to a vaster project related to the development of automated pipelines of information for European infrastructure in the form of digital twins. The outcome of this laboratory test results is of great use when developing similar automated pipelines of information in real sites including cable nets in roofs.All authors acknowledge the funding of ASHVIN, “Assistants for Healthy, Safe, and Productive Virtual Construction Design, Operation & Maintenance using a Digital Twin” an H2020 project under agreement 958161.Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version