Non-Adiabatic Capillary Tubes In Cycle Simulations

Capillary tubes including a suction line heat exchanger are typical expansion devices used in nowadays domestic refrigeration appliances. To account for their functionality in transient cycle simulations, including the highly transient start-up and shut-down operations, different capillary tube models and their implementation in such a cycle are investigated. These non-adiabatic capillary tube models comprise dimensionless correlations, neural network methods and one-dimensional homogeneous models which stem partly from open literature and from previous work of the authors. The difficulty in application of capillary models during off-design conditions is when two phase flow or even superheated vapor which enters the capillary tube. These conditions are not covered by most of the schemes. In this work a transient cycle simulation including a 1d formulation of the heat exchangers and a semi-empirical compressor model serves as virtual test bench for several capillary tube models. The range of parameters is chosen according to the need of domestic applications using R600a - mass flow rates range between 0 and 5 kg/h at inlet pressures up to 10 bar. The comparison of different implementation strategies is carried out in terms of speed, accuracy and stability in off-design. The predictability of the models is evaluated by steady state experimental data from literature and own experiments as well as an in-house 1d model for the regions where no measurements exist. It is concluded that the direct implementation of the 1d code bears the disadvantage of low speed, whereas common dimensionless correlations lose accuracy off its design point. Neural networks turn out to be a good trade-off between speed, reliability and accuracy

Transient 1D heat exchanger model for the simulation of domestic cooling cycles working with R600a

Generally, domestic refrigerators and freezers are running in non-continuous operation mode most of the time, which is a necessity to match cooling capacity to thermal loads. In currently available domestic appliances this matching is realized either by on/off or variable frequency control of the hermetic compressor, leading to a repetitive and transient change of the system state. On the other hand, if the runtimes of the compressor are longer because cooling capacity demand is high (e.g. pull down cycles, initial operation), steady state operating conditions might be reached. The cycling transients cause losses in system efficiency thus they should be reduced or avoided. To understand the complex transient physical processes and to optimize the cooling system efficiency, it turned out that the use of numerical methods is a promising approach. For this reason, a 1D heat exchanger model, which has been successfully implemented in a domestic cooling cycle simulation tool, is presented in this work. The heat exchanger model is a further development of the model being presented in Berger et al. (2012). The same mathematical framework is used for modelling the evaporator and condenser. In order to compute the void fraction, the pressure drop and the heat transfer special empirical models for evaporation and condensation, which are proposed in literature, have been implemented. Finally, the numerical predictions are compared to experimental data gained from a purpose-built test rig

Large scale multiplex PCR improves pathogen detection by DNA microarrays

<p>Abstract</p> <p>Background</p> <p>Medium density DNA microchips that carry a collection of probes for a broad spectrum of pathogens, have the potential to be powerful tools for simultaneous species identification, detection of virulence factors and antimicrobial resistance determinants. However, their widespread use in microbiological diagnostics is limited by the problem of low pathogen numbers in clinical specimens revealing relatively low amounts of pathogen DNA.</p> <p>Results</p> <p>To increase the detection power of a fluorescence-based prototype-microarray designed to identify pathogenic microorganisms involved in sepsis, we propose a large scale multiplex PCR (LSplex PCR) for amplification of several dozens of gene-segments of 9 pathogenic species. This protocol employs a large set of primer pairs, potentially able to amplify 800 different gene segments that correspond to the capture probes spotted on the microarray. The LSplex protocol is shown to selectively amplify only the gene segments corresponding to the specific pathogen present in the analyte. Application of LSplex increases the microarray detection of target templates by a factor of 100 to 1000.</p> <p>Conclusion</p> <p>Our data provide a proof of principle for the improvement of detection of pathogen DNA by microarray hybridization by using LSplex PCR.</p

Synthesis of Zeolites from Fine-Grained Perlite and Their Application as Sorbents

The hydrothermal alteration of perlite into zeolites was studied using a two-step approach. Firstly, perlite powder was transformed into Na-P1 (GIS) or hydro(xy)sodalite (SOD) zeolites at 100 °C and 24 h using 2 or 5 M NaOH solutions. Secondly, the Si:Al molar ratio of the reacted Si-rich solution was adjusted to 1 by Na-aluminate addition to produce zeolite A (LTA) at 65 or 95 °C and 6 or 24 h at an efficiency of 90 ± 9% for Al and 93 ± 6% for Si conversion. The performance of these zeolites for metal ion removal and water softening applications was assessed by sorption experiments using an artificial waste solution containing 4 mmol/L of metal ions (Me(2+): Ca(2+), Mg(2+), Ba(2+) and Zn(2+)) and local tap water (2.1 mmol/L Ca(2+) and 0.6 mmol/L Mg(2+)) at 25 °C. The removal capacity of the LTA-zeolite ranged from 2.69 to 2.86 mmol/g for Me(2+) (=240–275 mg/g), which is similar to commercial zeolite A (2.73 mmol/g) and GIS-zeolite (2.69 mmol/g), and significantly higher compared to the perlite powder (0.56 mmol/g) and SOD-zeolite (0.88 mmol/g). The best-performing LTA-zeolite removed 99.8% Ca(2+) and 93.4% Mg(2+) from tap water. Our results demonstrate the applicability of the LTA-zeolites from perlite for water treatment and softening applications

Probing the local structure: macromolecular combs in external fields

Recent experimental methods allow to monitor the response of macromolecules to locally applied fields, complementing usual, mesoscopic techniques. Based on the Rouse-model and its extension to generalized Gaussian structures (GGS), we follow here the stretching of comb macromolecules under local fields. This leads to a wealth of informations about the structure: Namely, given the inhomogeneous architecture of combs, the dynamics and amount of stretching depend strongly on the position of the monomer on which the external fields act. We discuss both the theoretical and the experimental implications of our findings, given that micromanipulations can be supplemented by fluorescence measurements, which are very sensitive to changes in the intramolecular distances.Comment: 16 pages, 5 pdf figures, to appear in Chem. Phy

IHK-Praxistipps zur Fachkräftesicherung: Arbeitgeberattraktivität steigern in 3 Schritten : Wegweiser für kleine und mittelständische Unternehmen

Der vorliegende Wegweiser gibt in drei Schritten Anregungen für Ihre Personalarbeit: Kennen Sie Ihre Mitarbeiterstruktur und die Bedürfnisse Ihrer Mitarbeiter (Schritt 1), können Sie gezielt Maßnahmen zu deren Bindung umsetzen (Schritt 2). Kennen Sie die Motivation von Bewerbern, können Sie diese leichter für Ihr Unternehmen gewinnen (Schritt 3). Für den Beginn ist es sinnvoll, Schwerpunkte zu setzen und in kleinen Schritten vorzugehen – einzelne Maßnahmen und Entscheidungshilfen werden in diesem Wegweiser vorgestellt

Transcatheter Aortic Valve Replacement Using Transaortic Access

OBJECTIVES The Registry of the Utilization of the TAo-TAVR approach using the Edwards SAPIEN Valve (ROUTE) was established to assess the effectiveness and safety of the use of transaortic (TAo) access for transcatheter aortic valve replacement (TAVR) procedures (NCT01991431). BACKGROUND TAVR represents an alternative to surgical valve replacement in high-risk patients. Whereas the transfemoral access route is used commonly as the first-line approach, transapical access is an option for patients not suitable for transfemoral treatment mainly due to anatomic conditions. TAo-TAVR has been shown to be a viable alternative surgical access route; however, only limited data on its effectiveness and safety has been published. METHODS ROUTE is a multicenter, international, prospective, observational registry; data were collected from 18 centers across Europe starting in February 2013. Patients having severe calcific aortic stenosis were documented if they were scheduled to undergo TAo-TAVR using an Edwards SAPIEN XT or a SAPIEN 3 valve. The primary endpoint was 30-day mortality. Secondary endpoints were intraprocedural or in hospital and 30-day complication rates. RESULTS A total of 301 patients with a mean age of 81.7 +/- 5.9 years and an Society of Thoracic Surgeons score of 9.0 +/- 7.6% were included. Valve success was documented in 96.7%. The 30-day mortality was 6.1% (18/293) (procedure-related mortality: 3.1%; 9 of 293). The Valve Academic Research Consortium-2 defined complications included myocardial infarction (1.0%), stroke (1.0%), transient ischemic attack (0.3%), major vascular complications (3.4%), life-threatening bleeding (3.4%), and acute kidney injury (9.5%). In 3.3% of patients, paravalvular regurgitation was classified as moderate or severe (10 of 300). Twenty-six patients (8.8%) required permanent pacemaker implantation. CONCLUSIONS TAo access for TAVR seems to be a safe alternative to the transapical procedure. (C) 2016 by the American College of Cardiology Foundation.Peer reviewe

Integrating Lidar and Atmospheric Boundary Layer Measurements to Determine Fluxes and Dynamics of Particulate Emissions from an Agriculture Facility

Lidar technology offers the ability to quantify concentrations of small particulates in the atmosphere in certain ranges of time and space. While this is a valuable tool to visualize the behavior of plumes emitted from the surface, the actual flux of particles cannot be estimated from such data alone. To determine the mass flux of particles, the concentrations must be properly integrated with wind and turbulence properties. The goal of this study is to utilize a model that uses wind and particle density information to calculate the flux of particles from an animal facility near Ames, Iowa. The model is a simplified conservation equation for particle density in the atmosphere. This approach essentially quantifies fluxes in and out of a box centered over the facility and estimates the surface source by assuming conservation of mass. In addition, we hypothesize that distinct turbulence structures will sometimes interact with the intermittency of the surface emission from the buildings, resulting in episodic changes in emission fluxes from the site. A second objective involves documenting how intermittent the emission plumes are and how they are connected to periodic large scale turbulence events. Lidar data of particle size and density in the vicinity of the site were collected during an intensive field campaign lasting nearly 2 weeks. In addition to the lidar data, turbulence data were measured at several levels on each of three towers, located upwind, inside and downwind of the source area. The model requires measurements of the vertical profiles of both concentrations of particulates and the mean horizontal wind. The concentrations were measured using the lidar, while winds were measured using a combination of cup anemometers and sonic anemometers. This allows the emission fluxes to be calculated during 15 to 30 minute periods when winds are consistent. Flux calculations await the final calibration of the lidar returns using measured particle densities. Flux estimates will be made when distinct plumes are observed under steady-state wind conditions. Current results are presented showing evidence of episodic plumes of CO2 in response to intermittent vertical motions of turbulences