External Chamber Research Articles

Thermal efficiency of a modified thermal storage wall containing phase change material in comparative test periods

The article presents the results and analysis of comparative tests carried out on a thermal storage wall modified with phase change material (PCM) in a selected time interval. These tests were carried out in real climatic conditions in external research chambers. The same transitional period has been compared, two consecutive calendar years, 2017 and 2018. The months of March and April were used for the analysis, which are characterized by large fluctuations of temperatures between day and night. Based on meteorological data for the Rzeszów-Jasionka station, the months of March and April are characterized by a longer period of sunshine and significant temperature fluctuations, which qualifies these months in the transition period for moderate climate in Poland. Selected physical parameters characterizing the influence of phase change materials on the thermal efficiency of a modified barrier were analysed. Analysis of selected parameters confirmed the repeated, beneficial effect of PCM on the stabilization of temperature in the internal space in selected research periods.

Single-cell microscopy of suspension cultures using a microfluidics-assisted cell screening platform.

Studies that rely on fluorescence imaging of nonadherent cells that are cultured in suspension, such as Escherichia coli, are often hampered by trade-offs that must be made between data throughput and imaging resolution. We developed a platform for microfluidics-assisted cell screening (MACS) that overcomes this trade-off by temporarily immobilizing suspension cells within a microfluidics chip. This enables high-throughput and automated single-cell microscopy for a wide range of cell types and sizes. As cells can be rapidly sampled directly from a suspension culture, MACS bypasses the need for sample preparation, and therefore allows measurements without perturbing the native cell physiology. The setup can also be integrated with complex growth chambers, and can be used to enrich or sort the imaged cells. Furthermore, MACS facilitates the visualization of individual cytoplasmic fluorescent proteins (FPs) in E. coli, allowing low-abundance proteins to be counted using standard total internal reflection fluorescence (TIRF) microscopy. Finally, MACS can be used to impart mechanical pressure for assessing the structural integrity of individual cells and their response to mechanical perturbations, or to make cells take up chemicals that otherwise would not pass through the membrane. This protocol describes the assembly of electronic control circuitry, the construction of liquid-handling components and the creation of the MACS microfluidics chip. The operation of MACS is described, and automation software is provided to integrate MACS control with image acquisition. Finally, we provide instructions for extending MACS using an external growth chamber (1 d) and for how to sort rare cells of interest.

Statistics of the Current Induced Within a Partially Shielded Enclosure in a Reverberation Chamber

The statistics of the current induced on conducting wires and surfaces within a partially shielded enclosure by aperture coupling of an ideally random, mechanically stirred reverberation chamber electromagnetic field has been considered. A robust discretization of the plane-wave spectral representation of the chamber field confirms that the magnitude of the induced current at a test point follows a Rayleigh distribution provided that the equipment under test (EUT) is composed entirely of electromagnetically linear materials and mechanical or spatial stirring of the external chamber field is used, independent of the sizes of the EUT and coupling aperture. The discrete spectrum gives an efficient method to numerically find the statistics of the currents on or within arbitrarily shaped EUTs. Experimental measurement of the induced currents on a sample EUT within a mechanically stirred reverberation chamber confirms the validity of the discrete-plane-wave spectral method of predicting the current statistics at low and high frequencies. Addition of frequency stirring introduces a fundamental difference in the operation of a reverberation chamber test that leads to non-Rayleigh sample statistics when highly resonant EUTs are considered.

Establishing IAEA TRS-457 diagnostic X-ray beam qualities at the Australian primary standard dosimetry laboratory.

This paper reports the process and findings in establishing the diagnostic beam qualities for the calibration of diagnostic dose meters in the Australian primary standard dosimetry laboratory at the Australian Radiation Protection and Nuclear Safety Agency, ARPANSA. A novel iterative method to achieve the RQR beam quality requirements described by IEC 61267 is presented. The correction factors for the primary standard free-air chamber and their uncertainties are reported. The calibration procedure with detailed uncertainty budget of a typical diagnostic ionisation chamber (model PTW 34060) is reported. Beam profile measurements and details of the use of an external monitor chamber (model PTW 34014) are also reported. The uncertainty in the ARPANSA calibration coefficients is estimated to be 1.2% at k = 2 for both RQR and RQA beam qualities. The laboratory is now able to provide calibration services for radiation detectors used in general X-ray radiography.

Simultaneous determination of rutin and ascorbic acid in a sequential injection lab-at-valve system

A green, simple, accurate and highly sensitive sequential injection lab-at-valve procedure has been developed for the simultaneous determination of ascorbic acid (Asc) and rutin using 18-molybdo-2-phosphate Wells-Dawson heteropoly anion (18-MPA). The method is based on the dependence of the reaction rate between 18-MPA and reducing agents on the solution pH. Only Asc is capable of interacting with 18-MPA at pH 4.7, while at pH 7.4 the reaction with both Asc and rutin proceeds simultaneously. In order to improve the precision and sensitivity of the analysis, to minimize reagent consumption and to remove the Schlieren effect, the manifold for the sequential injection analysis was supplemented with external reaction chamber, and the reaction mixture was segmented. By the reduction of 18-MPA with reducing agents one- and two-electron heteropoly blues are formed. The fraction of one-electron heteropoly blue increases at low concentrations of the reducer. Measurement of the absorbance at a wavelength corresponding to the isobestic point allows strictly linear calibration graphs to be obtained. The calibration curves were linear in the concentration ranges of 0.3–24mgL−1 and 0.2–14mgL−1 with detection limits of 0.13mgL−1 and 0.09mgL−1 for rutin and Asc, respectively. The determination of rutin was possible in the presence of up to a 20-fold molar excess of Asc. The method was applied to the determination of Asc and rutin in ascorutin tablets with acceptable accuracy and precision (1–2%).

Combined Chemical Looping: New Possibilities for Energy Storage and Conversion

A novel concept of energy storage and conversion was demonstrated in a laboratory-scale test. The proposed combined chemical looping is able to store and release energy from chemical looping combustion for heat generation and hydrogen production by steam–iron processes integrated in one reactor. The reactor contains two concentric chambers, which are both filled with iron-based material. In a first step, all material is reduced to the metallic form, thus “charging” the reactor. For the second step or “discharging”, steam is fed to the inner chamber and air is fed to the outer chamber. The inner chamber is used for hydrogen production, and the external chamber is used for heat generation. In addition to iron, the external chamber contains a highly pyrophoric Ni-based layer at the air entry point to enable the startup of heat generation at room temperature. This concept of combined chemical looping was successfully tested: heat was generated by metal oxidation in air, and H2 was produced following contact o...

Muscle Microvascular Blood Flow, Oxygenation, pH, and Perfusion Pressure Decrease in Simulated Acute Compartment Syndrome.

The current gold standard for diagnosing acute compartment syndrome (ACS) is an assessment of clinical signs, invasive measurement of intramuscular pressure (IMP), and measurement of local perfusion pressure. However, IMP measurements have several shortcomings, including pain, risk of infection, risk of technique error, plugging of the catheter tip, lack of consensus on the diagnostic pressure threshold, and lack of specificity and sensitivity. The objective of this study was to evaluate muscle hemodynamics, oxygenation, and pH as diagnostic parameters in a human model of ACS. We hypothesized that as IMP increases, muscle microvascular blood flow, oxygenation, and pH decrease in the anterior compartment of a leg at heart level and that they decrease significantly more when the leg is elevated further. An external pneumatic leg pressure chamber, combined with a venous stasis thigh cuff, was used to increase IMP and simulate ACS. Eight healthy subjects (5 males and 3 females; mean age, 26 years) had photoplethysmography and near-infrared spectroscopy-pH sensors placed over the middle aspect of the tibialis anterior muscle of the right (experimental) and left (control) legs. Leg chamber pressure conditions (40, 50, and 60 mm Hg) were applied in a randomized order after baseline measurements were taken. Data were collected continuously for each 11-minute pressure condition, with an 11-minute recovery period after each condition, and the average of the last 6 minutes was used for data analyses. The same protocol was repeated with each subject's legs elevated 12 cm above heart level. Data were analyzed using repeated-measures analysis of variance (ANOVA). As IMP increased, muscle microvascular blood flow (p = 0.01), oxygenation (p < 0.001), and pH (p < 0.001) all decreased significantly in the experimental leg compared with the control leg. At all IMP levels, leg elevation significantly decreased muscle oxygenation (p = 0.013) and perfusion pressure (p = 0.03) compared with the control leg at heart level. These results indicate that muscle microvascular blood flow, oxygenation, pH, and perfusion pressure decrease significantly as IMP increases in a human model of ACS. This study identifies hemodynamic and metabolic parameters as potential noninvasive diagnostic tools for ACS.

Natural-gas heating of cupola furnaces for more energy-efficient iron production

Natural gas is employed to reduce coke consumption in cupola furnaces with an open or closed top. The usual approach here is combustion of the natural gas by means of burners in external chambers at the perimeter of the furnace housing. Depending on their design, the burners ensure partial or complete preliminary mixing of the gas and air, with an air excess of 1.2–1.5. Then the combustion products are sent directly to the batch bed. In this system, the coke consumption amounts to 8–9% of the metal charge, while the consumption of gaseous fuel is 30–40 m3/t of melt. In these conditions, the melt temperature rises slightly (by 10–20°C); the productivity is increased by 15–20%; and the harmful gas emissions (mainly CO) are reduced by 20–25%. The gas dynamics of the cupola furnace is periodically disrupted, with suspension of the batch bed, cooling of the melt produced, less complete chemical combustion, and damage to the furnace lining. When using this method, the gas–air mixture is supplied to the hot bed with an air excess no lower than 2.5–3.0. A high-temperature zone (1350–1380°C) of width 60–70 mm is formed and moves through the bed at a speed of 15–20 mm/min. This calls for uniform mixing of the gas and air, specific gas-dynamic conditions, and the creation of the required gas–air ratio, with an air excess of more than 2.5–3.0. If cold gas–air mixture is supplied to the furnace bed through a tuyere, the combustion zone divides the whole bed into two stages: the initial and final stages. The high temperature of the combustion zone ensures fast cooling of the material at ignition of the gas–air mixture. That prevents ignition in the space above the bed. The lack of direct contact between the high-temperature zone and the furnace’s working space improves the reliability and economic indices of this process (no heat losses). Bed combustion of natural gas in the heating of such cupola furnaces increases the productivity from 10 to 13.6 t/h (by 36%), with reduction in coke consumption by 80 kg/t (33.3%) and decrease in heat consumption by 25 kW (18.78%). The heat losses with the exhaust gases are reduced by 25.32 kW (16.2%). The total thermal efficiency of the system is increased from 35.58 to 42.26% (by 15.81%, rel.).

Long-term dosimetric stability of multiple TomoTherapy delivery systems.

The dosimetric stability of six TomoTherapy units was analyzed to investigate changes in performance over time and with system upgrades. Energy and output were tracked using monitor chamber signal, onboard megavoltage computed tomography (MVCT) detector profile, and external ion chamber measurements. The systems (and monitoring periods) include three Hi‐Art (67, 61, and 65 mos.), two TomoHDA (31 and 26 mos.), and one Radixact unit (11 mos.), representing approximately 10 years of clinical use. The four newest systems use the Dose Control Stability (DCS) system and Fixed Target Linear Accelerator (linac) (FTL). The output stability is reported as deviation from reference monitor chamber signal for all systems and/or from an external chamber signal. The energy stability was monitored using relative (center versus off‐axis) MVCT detector signal (beam profile) and/or the ratio of chamber measurements at 2 depths. The clinical TomoHDA data were used to benchmark the Radixact stability, which has the same FTL but runs at a higher dose rate. The output based on monitor chamber data of all systems is very stable. The standard deviation of daily output on the non‐DCS systems was 0.94–1.52%. As expected, the DCS systems had improved standard deviation: 0.004–0.06%. The beam energy was also very stable for all units. The standard deviation in profile flatness was 0.23–0.62% for rotating target systems and 0.04–0.09% for FTL. Ion chamber output and PDD ratios supported these results. The output stability on the Radixact system during extended treatment delivery (20, 30, and 40 min) was comparable to a clinical TomoHDA system. For each system, results are consistent between different measurement tools and techniques, proving not only the dosimetric stability, but also these quality parameters can be confirmed with various metrics. The replacement history over extended time periods of the major dosimetric components of the different delivery systems (target, linac, and magnetron) is also reported.

Thermodynamic simulation of a multi-step externally fired gas turbine powered by biomass

A thermodynamic model for a realistic Brayton cycle, working as an externally fired gas turbine fueled with biomass is presented. The use of an external combustion chamber, allows to burn dirty fuels to preheat pure air, which is the working fluid for the turbine. It also avoids direct contact of ashes with the turbine blades, resulting in a higher life cycle for the turbine. The model incorporates a high temperature heat exchanger and an arbitrary number of turbines and compressors, with the corresponding number of intercoolers and reheaters. It considers irreversibilities such as non-isentropic compressions and expansions, and pressure losses in heat input and release. The composition and temperature of the combustion gases, as well as the variable flow rate of air and combustion gases, are calculated for specific biomasses. The numerical model for a single stage configuration has been validated by comparing its predictions with the data sheets of two commercial turbines. Results are in good agreement. Curves on the dependence of thermal efficiency and power output with the overall pressure ratio will be shown for several plant configurations with variable number of compression/expansion stages. Also the influence of different types of biomasses and their moisture will be analyzed on parameters such as fuel consumption and exhaust gases temperature. For a single step plant layout fueled with eucalyptus wood an efficiency of 23% is predicted, whereas for a configuration with two compressors and one turbine efficiency increases up to 25%. But it is remarkable that the latter leads to a 29% increase in power output.

Building a Graphite Calorimetry System for the Dosimetry of Therapeutic X-ray Beams

Abstract A graphite calorimetry system was built and tested under irradiation. The noise level of the temperature measurement system was approximately 0.08 mK (peak to peak). The temperature of the core part rose by approximately 8.6 mK at 800 MU (monitor unit) for 6-MV X-ray beams, and it increased as X-ray energy increased. The temperature rise showed less spread when it was normalized to the accumulated charge, as measured by an external monitoring chamber. The radiation energy absorbed by the core part was determined to have values of 0.798 J/μC, 0.389 J/μC, and 0.352 J/μC at 6 MV, 10 MV, and 18 MV, respectively. These values were so consistent among repeated runs that their coefficient of variance was less than 0.15%.

Comparing clear-water RAS and biofloc systems: Shrimp (Litopenaeus vannamei) production, water quality, and biofloc nutritional contributions estimated using stable isotopes

Indoor shrimp aquaculture systems can be used to produce fresh, never-frozen, quality shrimp near metropolitan seafood markets regardless of season and climate. However, questions still remain regarding what type of production system is best suited to maximize indoor production. In this project, two types of systems were compared: clear-water (CW) RAS and biofloc (BF) systems. Three, 1.36m3 tanks were assigned to each of the two treatments; CW tanks had external settling chambers, two foam fractionators, and external biofilters, all operated continuously. BF tanks had settling chambers and one foam fractionator which were operated as needed to control solids accumulation. Shrimp weighing 0.42g were stocked in all tanks at 250m−3 and grown for 55 days. Ammonia and pH levels were significantly (P<0.05) higher in the CW treatment, while nitrite, nitrate, and turbidity were all significantly higher in the BF treatment, although all parameters remained within acceptable ranges for shrimp growth. Shrimp mean harvest weight was significantly higher, biomass (kgm−3) was significantly greater, and FCR was significantly lower in the CW treatment; there were no significant differences in survival between treatments. Isotope levels indicated that shrimp in the BF treatment obtained a portion of the C (18-60%) and N (1-18%) in their tissues from biofloc material; however, this effect did not positively influence production in that treatment. By nearly eliminating solids from the water and using an external biofilter, substantially better water quality was maintained in the CW systems, which may have been a major contributor to the improved shrimp production in that treatment.

Updraft gasifier and ORC system for high ash content biomass: A modelling and simulation study

Ash content, and the problematic related to it are currently the most important drawbacks of biomass combustion. The present work carries out the modelling and simulation of an innovative CHP system composed of an updraft gasifier, an external combustion chamber and Organic Rankine Cycle (ORC) generator for the energetic valorization of olive leaves: a free and abundant by-product of the olive oil industry. The CHP system can produce 93.8kW of net electrical power and approximately 412kW of available thermal power for the heating necessities of a medium-sized olive oil mill. The CHP efficiency achieved is 58.41% and the net electrical efficiency 10.82% together with a biomass consumption of 240kg/h. Based on the simulation results, the producer gas reaches a suitable lower heating value (4.60MJ/kg) and a gasification efficiency of 88.10%. At the gasifier operating conditions, the producer gas presents the following mole composition: 12.8% H2, 19.2% CO, 2.6% CH4, 8.3% CO2, 11.8% H2O, 42.1% N2, 1.7% Tar and the rest Ar, O2, H2S, dust and particulates. The results from ORC simulations show a very good efficiency (18.7%) at 25bar of working pressure and 300°C of turbine inlet temperature. Toluene has been selected as suitable organic fluid for high temperature heat sources (>900°C). In this paper, an innovative energy recovery system for high ash content biomass has been theoretically developed, representing a good opportunity to promote distributed generation systems.

Dual chamber stent prevents organ malperfusion in a model of donation after cardiac death

The paradigm for donation after cardiac death subjects donor organs to ischemic injury. A dual-chamber organ perfusion stent would maintain organ perfusion without affecting natural cardiac death. A center lumen allows uninterrupted cardiac blood flow, while an external chamber delivers oxygenated blood to the visceral vessels. A prototype organ perfusion stent was constructed from commercial stents. In a porcine model, the organ perfusion stent was deployed, followed by a simulated agonal period. Oxygenated blood perfused the external stent chamber. Organ perfusion was compared between controls (n=3) and organ perfusion stent (n=6). Finally, a custom, nitinol, dual chamber organ perfusion stent was fabricated using a retrievable "petal and stem" design. Endovascular organ perfusion stent deployment achieved visceral isolation without adverse impact on cardiac parameters. Visceral oxygen delivery was 4.8-fold greater compared with controls. During the agonal period, organs in organ perfusion stent-treated animals appeared well perfused in contrast with the malperfused controls. A custom nitinol and polyurethane organ perfusion stent was recaptured easily with simple sheath advancement. An organ perfusion stent maintained organ perfusion during the agonal phase in a porcine model of donation after cardiac death organ donation without adversely affecting cardiac function. Ultimately, the custom retrievable design of this study may help resolve the critical shortage of donor organs for transplant.

A Computer Model of the Evaporator for the Development of an Automatic Control System

For the implementation of a closed nuclear fuel cycle it is necessary to carry out a series of experimental studies to justify the choice of technology. In addition, the operation of the radiochemical plant is impossible without high-quality automatic control systems. In the technologies of spent nuclear fuel reprocessing, the method of continuous evaporation is often used for a solution conditioning. Therefore, the effective continuous technological process will depend on the operation of the evaporation equipment. Its essential difference from similar devices is a small size. In this paper the method of mathematic simulation is applied for the investigation of one-effect evaporator with an external heating chamber. Detailed modelling is quite difficult because the phase equilibrium dynamics of the evaporation process is not described. Moreover, there is a relationship with the other process units. The results proved that the study subject is a MIMO plant, nonlinear over separate control channels and not selfbalancing. Adequacy was tested using the experimental data obtained at the laboratory evaporation unit.

SU‐F‐P‐11: Long Term Dosimetric Stability of 6 TomoTherapy Systems

Purpose:The dosimetric stability of six TomoTherapy units was analyzed to investigate changes in performance over time and with system upgrades.Methods:Energy and output were tracked using monitor chamber signal, onboard MVCT detector signal and external ion chamber measurements. The systems (and monitoring periods) include 3 Hi‐Art (67, 61 and 65 mos.), 2 HDA (29 and 25 mos.) and one research unit (7 mo.). Dose Control Stability system (DCS) was installed on 4 systems. Output stability is reported as deviation from reference monitor chamber signal for all systems, and from an external chamber for 4 systems. Energy stability was monitored using the relative (center versus off‐axis) MVCT detector signal and/or the ratio of chamber measurements at 2 depths. The results from the clinical systems were used to benchmark the stability of the research unit, which has the same linear accelerator but runs at a higher dose rate.Results:The output based on monitor chamber data of all six systems is very stable. Non‐ DCS had a standard deviation of 1.7% and 1.8%. As expected, DCS systems had improved standard deviation: 0.003–0.05%. The energy was also very stable for all units. The standard deviation in exit detector flatness was 0.02–0.3%. Ion chamber output and 20/10 cm ratios supported these results. The stability for the research system, as monitored with a variety of metrics, is on par with the existing systems.Conclusion:The output and energy of six TomoTherapy units over a total of almost 10 years is quite stable. For each system, the results are consistent between the different measurement tools and techniques, proving not only the dosimetric stability, but that these quality parameters can be confirmed with various metrics. A research unit operating at a higher dose rate performed as well as the clinical treatment units.University of Wisconsin and Accuray Inc. (vendor of TomoTherapy systems) have a research agreement which supplies funds for research to the University. This project was partially supporting with these funds.

Changing light levels induce photo-oxidative stress and alterations in shell density of Amphistegina lobifera (Foraminifera)

Light is an important factor limiting the distribution of holobiont (host-algae) organisms in marine environments. Reef-dwelling large benthic foraminifera (LBF) are particularly sensitive to changes in light exposure, but their cryptic behaviour allows them to colonise different habitats across a light gradient. Yet, how foraminifera of the same species that live in different habitats respond to variations in light conditions, and the physiological and morphological attributes that govern that response, remain unclear. Here, we investigate how Amphistegina lobifera, a common and abundant LBF species in reef environments, collected from different reef sites across a light gradient, respond to changing light levels under lab-controlled conditions. Reduced light below their optimum level for growth and calcification caused a significant reduction in antioxidant capacity, and a significant decline in the density of newly added chambers. In contrast, elevated light caused significant reduction in survivorship, induced bleaching and photo-oxidative stress, and caused thickening of external chambers. Reef site did not have a significant effect on most of the responses, and populations collected from different reef sites showed similar sensitivity to changes in irradiance below and above their optimum level. The capacity to regulate symbiont density and to host a diversity of symbiotic diatoms within Amphistegina could be a reason for their ability to acclimate rapidly to different light levels. However, prolonged exposure to reduced light may result in a decrease in shell density and, as a consequence, a decline in carbonate production in reef environments.

Effect of fluoroscopic X-ray beam spectrum on air-kerma measurement accuracy: implications for establishing correction coefficients on interventional fluoroscopes with KAP meters.

The first goal of this study was to investigate the accuracy of the displayed reference plane air kerma (Ka,r) or air kerma‐area product (Pk,a) over a broad spectrum of X‐ray beam qualities on clinically used interventional fluoroscopes incorporating air kerma‐area product meters (KAP meters) to measure X‐ray output. The second goal was to investigate the accuracy of a correction coefficient (CC) determined at a single beam quality and applied to the measured Ka,r over a broad spectrum of beam qualities. Eleven state‐of‐the‐art interventional fluoroscopes were evaluated, consisting of eight Siemens Artis zee and Artis Q systems and three Philips Allura FD systems. A separate calibrated 60 cc ionization chamber (external chamber) was used to determine the accuracy of the KAP meter over a broad range of clinically used beam qualities. For typical adult beam qualities, applying a single CC determined at 100 kVp with copper (Cu) in the beam resulted in a deviation of <5% due to beam quality variation. This result indicates that applying a CC determined using The American Association of Physicists in Medicine Task Group 190 protocol or a similar protocol provides very good accuracy as compared to the allowed ±35% deviation of the KAP meter in this limited beam quality range. For interventional fluoroscopes dedicated to or routinely used to perform pediatric interventions, using a CC established with a low kVp (∼55−60 kVp) and large amount of Cu filtration (∼0.6−0.9 mm) may result in greater accuracy as compared to using the 100 kVp values. KAP meter responses indicate that fluoroscope vendors are likely normalizing or otherwise influencing the KAP meter output data. Although this may provide improved accuracy in some instances, there is the potential for large discrete errors to occur, and these errors may be difficult to identify.PACS number(s): 87.59.C‐, 87.59.cf, 87.53.Bn

A Small Size Combined System for the Production of Energy from Renewable Sources and Unconventional Fuels

Nowadays, the development of new power plants capable of effectively using non-conventional energy sources is strongly desirable in order to obtain a significant reduction in costs of energy. In this regard, this paper proposes a new small scale (about 100kW) combined cycle plant which can be fired externally by any kind of biomass. Particularly, the research activity presented here is concerned with the preliminary design of this innovative plant, which will be built, by means of a project funded by “Apulia Region”, at the LabZero Research Centre of Polytechnic University of Bari in the south of Italy. The goal of the paper is to demonstrate the effectiveness of the plant in terms of energy efficiency and availability and reliability of its components. The plant is mainly composed of a centrifugal compressor and a centripetal turbine of an automotive turbocharger, with the working fluid (clean air) being heated in a high temperature heat exchanger (HTHE) by using hot flue gases produced in an external combustion chamber burning biomass. The clean hot air expands in the turbine and then feeds the combustion chamber, where biomass is burned. In order to increase the efficiency, the flue gases exiting the HTHE are delivered into a heat recovery steam generator to generate water steam which can finally expand through a rotary actuator. Two configurations, employing an open Rankine cycle and a close one respectively, are analysed, and the use of biomass is compared with methane.

An experimental set-up to analyse the oxygen consumption of elastomers during ageing by using a differential oxygen analyser

Ageing of polymers becomes more and more important. This can be seen by the increasing number of research projects dealing with this topic. However, the influence of oxygen on changes in the mechanical performance is undisputable and important with respect to the lifetime of polymer products. Therefore, a respirometer offers the potential to detect the smallest amounts of oxygen changes in the polymers’ ambient air. It will be used to analyse the oxygen consumption of rubber which is exposed for different times to elevated temperatures. In this contribution, virgin rubber samples are aged for various times in a sealed chamber at temperatures of 60, 80 and 100°C. The decline of the oxygen concentration in the ambient air is measured by flushing the chamber with dried and cleaned air which is conducted into the respirometer. The oxygen concentration is compared with that in a reference chamber, which is exposed to the same ageing conditions as the sample under investigation. The absorbed oxygen is relevant for ageing and a considerable factor for further investigations. For this reason, an experimental set-up using a differential oxygen analyser is developed, which allows for ageing several samples simultaneously in external climate chambers. The comparison of the change in the mechanical material behaviour after ageing can provide an important contribution for improving constitutive models or ongoing researches on the fatigue strength of polymers. This work shows the development of an improved method for combining mechanical testing and the measurement of oxygen consumption.