A reliable evaluation of thermal behaviour and energy efficiency of buildings depends on the accurate thermal characterization of the envelope components. One of the most reliable methodologies to ...perform this thermal characterization is the measurements under laboratory-controlled conditions. The thermal performance assessment of lightweight steel-framed (LSF) building components exhibits particular additional challenges related to the strong thermal conductivity contrast between cavity insulation and steel frame materials, which may originate unwanted significant thermal bridge effects. The use of thermal break (TB) strips is one of the most currently used thermal bridge mitigation strategies. It was not found in the literature any experimental campaign for TB strips thermal performance evaluation in LSF elements. In this paper the thermal performance of twenty load-bearing (LB) and non-load-bearing (NLB) LSF walls configurations are measured, using the heat flow meter (HFM) method under controlled laboratory conditions. Three thermal break (TB) strip materials and three TB strip locations in the steel stud flanges are assessed. It was found that the inner and outer TB strips show very similar thermal performances, while double TB strips have a relative significant thermal performance increase. Aerogel was the best performance TB material, exhibiting a substantial improvement relatively to recycled rubber and cork/rubber composite TB strips. Furthermore, the TB strips performance was identical for the evaluated structural (LB) and non-structural (NLB) LSF walls.
•The R-values of twenty load- and non-load-bearing (NLB) LSF walls configurations are measured.•Three thermal break (TB) strip materials and three TB strip locations are assessed.•The inner and outer TB strips show very similar thermal performances.•The double TB strips have a relatively significant thermal performance increase.•Aerogel was the best performance TB material, exhibiting a substantial improvement relative to others.
The photovoltaic (PV) technology has made considerable progress during the recent years in both grid connected and stand-alone applications, especially in areas of high local solar potential. In this ...context, the interest recently demonstrated in the Greek region concerning PVs encourages the investigation of optimum operation conditions for such systems. At the same time, summer-only applications, being rather common in Greece, require maximum exploitation of the local solar potential during the specific period of the year. For this purpose, an experimental study is currently carried out in the area of Athens, in order to evaluate the performance of different PV panel tilt angles during the summer period. According to the experimental results obtained, the angle of 15° (±2.5°) is designated as optimum for almost the entire summer period, while conclusions drawn are accordingly theoretically validated by means of established solar geometry equations.
► The Greek PV market has during the last years made considerable progress. ► Seasonal needs of electricity only during summer are common in several applications. ► Selection of the optimum summer PV panels’ tilt angle is of major importance. ► Experimental measurements are carried out during the entire summer period. ► Experimental results are accordingly theoretically validated.
The objective of this experimental study consists in investigating the effects of torrefaction treatment on two different woody biomass chosen from softwood as spruce pine and annual grass ...lignocellulosic hardwood as reed. This thermal pre-treatment has been conducted in a small batch reactor directly fluxed by a controlled nitrogen flow. Tests have been carried out at different temperatures, ranging from 250°C to 310°C, and reaction time from few minutes to 1h. Properties involved in this investigation are ultimate analysis, thermal quantities among which caloric value (HHV), fibers distribution and equilibrium moisture content. The obtained results confirm that torrefaction is a viable thermal pre-treatment to upgrade biomass and looks promising for a new generation of biomass derived fuel. As main topic, this research focuses on evaluating the role of the Mass Yield (MY) as synthetic parameter of the process. In particular it is made evidence that the properties of the torrefied samples can be led back to the MY without making reference to their thermal-time pathway. As example, considering two samples presenting the same MY of 80%, the former torrefied at 280°C for 76min, the second at 310°C for 17min, it is verified that the values of the aforementioned properties are very similar for both the samples even if submitted to different thermal pathways. The potentiality of the MY has been enhanced by extending this investigation to additional species of biomass pertaining to two groups, woody biomass and non-woody biomass. Inside the conditions ranges of the proposed experimental tests and for each of the indicated biomass type, an accurate linear correlation is obtained between MY and Energy Yield (EY) with a determination coefficient of (R2) 0.98 and 0.97 for woody and non-woody biomass respectively.
Besides confirming the benefit of the torrefaction in enhancing the quality of the treated biomass, the use of the MY as synthetic parameter can be exploited to improve the torrefaction modeling schemes and to optimize the selection of the process working conditions. The proposed approach can therefore be useful to examine the relevant amount experimental data till now produced on this issue in view of exploiting and orienting their use towards real scale plant design.
As nanotechnology is applied clinical medicine, nanoparticle-based therapy is emerging as a novel approach for the treatment of atherosclerosis. Ligand–receptor interaction affects the effectiveness ...of nanoparticle targeting therapy. In this study, the biomimetic peptide (BP-KFFVLK-WYKDGD) ligand specifically targeting the lysophosphatidylcholine (LPC) receptor in atherosclerotic plaques was constructed. The corresponding ligand–receptor interaction under different pH values was investigated by molecular dynamics simulation and experimental measurements. Results show that the interaction force between the peptide and LPC is greater than that of the peptide and human umbilical vein endothelial cell, clearly demonstrating the specific targeting of the peptide ligand to the LPC receptor. The ligand–receptor binding of peptide and LPC dominantly depends on Coulomb and van der Waals interactions. The YKDG amino acids of the peptide are the main fragment that binds to LPC. Compared with neutral environment at pH 7.4, the interaction forces between the peptide and oxidized low-density lipoprotein (oxLDL) decreased by 18.22 % and 45.87 % under acidic environments at pH 6.5 and 5.5, respectively, because of the change in oxLDL secondary structure and the release of LPC from oxLDL. Nevertheless, the peptide still has a strong binding capacity with oxLDL for the treatment of atherosclerosis.
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•The mechanism of peptide-LPC interaction is explored by simulation and experiment.•YKDG amino acid residues of peptide are the main sequence that binds to LPC.•The interaction of peptide-oxLDL is smaller at acidic pH than that at neutral pH.•In acidic environments, peptide and oxLDL still have strong binding ability.•LPC shedding from oxLDL is the reason for reducing the peptide-oxLDL interaction.
•Heat transfer measurements at the corner of a wooden building in a hot box.•Sinusoidal temperature variation over time.•Evaluation of the dynamic thermal bridging effect.•Higher thermal phase lag ...and thermal amplitude near the corner.
In this paper the dynamic thermal behavior of a Linear Thermal Bridge (LTB) in a wooden building corner is evaluated experimentally. The tests were performed in the laboratory using a calibrated hot box. The temperatures imposed on the external and the internal environmental sides were controlled by a climatic chamber and a heating system, respectively. The internal surface temperatures were recorded using a series of thermocouples connected to a data logger system. The heat flow through the wooden corner was measured by heat flux sensors. The dynamic thermal bridging effect was then evaluated by comparing the heat responses near the corner with those at the adjacent plane walls.
The experimental results were compared with the numerical responses obtained with a boundary element method (BEM) model developed by the authors. This comparison showed good agreement between the two methods. The BEM model was then used to examine the influence of the thermal insulation on the dynamic thermal behavior of the wooden corner. The results show that the thermal amplitude is higher near the corner, even when thermal insulation is used.
Many researchers have considered air quality degradation due to the emission of fine particles from industrialized and urban areas during recent decades. Recently, the European Parliament has had ...concerns about ensuring a healthy human environment. Therefore, the experimental and theoretical investigations of the dynamics of fine particulate matter are for determining efficient monitoring and cleaning air from industrially generated air pollutants. These investigations also imply the use of alternate methods that stimulate fine particle agglomeration. One of the methods is the use of acoustics. Many experimental investigations of particles with a diameter between 1 and 10μm have proven that the use of acoustic agglomeration increases the particle size. Then, conventional air filters can be used to collect the larger particles. This process improves the collection efficiency of the particles. Particulate agglomeration chamber consisting of an acoustic field generator and an inner part was created for the test particles of diesel engines (range from 0.3 to 10μm). Modeling of its elements was performed using Comsol multifunctional software. This sound pressure level is enough 1 to lead the acoustic agglomeration process of particles in the measurable range from 0.3 to 10μm. The sound pressure level reach this value (130–140dB) at the acoustic agglomeration zone.
Additionally, the theoretical evaluation of the agglomeration time of two sub-micron particles enabled the estimation of efficient agglomeration of particles with sizes between 0.3 and 10μm during the measurement period. A starting value of 136dB of sound pressure level (SPL) was created in the experimental chamber with the turbulence condition, where SPL values were measured by using the Bruel&Kjaer measurement system “Type 9727” with hydrophone 8104. The observation concentrations of diesel engine exhaust particles in the experimental chamber with and without acoustic influence were performed using Particle Concentration Analyzer 4 APC ErgoTouch Pro 2.
The results of experimental research shows that the acoustic agglomeration effect formed the proper conditions for the agglomeration of particles of all diameters (0.3, 0.5, 1.0, 3.0, 5.0 and 10μm).
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•The IC (internal combustion) engine exhaust particle emissions are considered.•An acoustic generator for the agglomeration of particles was created and validated.•Acoustic agglomeration produces about 140dB of sound pressure at 24kHz frequency.•The agglomeration of particles (0.3–10μm) approved by experimental studies.
Spectrum sensing and transmit notching is a form of cognitive radar that seeks to reduce mutual interference with other spectrum users in the same band. This concept is examined for the case where ...another spectrum user moves in frequency during the radar's CPI. The physical radar emission is based on a recent FM noise waveform possessing attributes that are inherently robust to sidelobes that otherwise arise for spectral notching. Due to increasing spectrum sharing with cellular communications, the interference considered takes the form of in-band OFDM signals that hop around the band. The interference is measured each PRI and a fast spectrum sensing algorithm determines where notches are required, thus facilitating a rapid response to dynamic interference. To demonstrate the practical feasibility and to understand the trade-space such a scheme entails, free-space experimental measurements based on notched radar waveforms are collected and synthetically combined with separately measured hopping interference under a variety of conditions to assess the efficacy of such an approach, including the impact of interference hopping during the radar CPI, latency in the spectrum sensing/waveform design process, notch tapering to reduce sidelobes, notch width modulation due to spectrum sensing, and the impact of digital up-sampling on notch depth.
•Coupled thermo-hydraulic CFD simulations of single radiator panel.•Complete radiator convective heat dissipation simulated with LES turbulence model.•Jointed semi-analytical model/CFD simulations ...provide an accurate analysis tool.•Experimental measurements of different key variables on a power workbench.•Turbulence between panels unable to supply fresh air into thermal boundary layer.
This paper presents semi-analytical calculations, computational fluid dynamic simulations and experimental measurements accomplished on a typical 30MVA power transformer. An ad hoc workbench was devised to carry out the experimental measurements. This facility allowed to estimate the values of different key variables involved in heat dissipation within the radiator, like convective heat transfer coefficients, oil-flow rate, air-flow speed between radiator fins and overall dissipated heat, among others. The main objectives of the study are to analyze the cooling capacity of the current radiator design working in ONAN mode and to validate the numerical simulation and calculation procedures for further design optimizations. The coupled thermo-hydraulic numerical simulations were performed on a computer cluster due to the high computational cost of the resulting models. The results of the simulations show good agreement with the experimentally measured values and with those obtained with the semi-analytical model, thus confirming that this model together with the CFD simulations are an accurate analysis tool. The heat transfer coefficients in the oil, the radiator panel and the air are computed. It is found that convective heat transfer from the panel to the air is approximately 10 times lower than heat transfer in the oil. Possible improvements on the current radiator design are briefly mentioned.
•Parametric experimental study varying the cavity geometry and working temperature.•Large set of experimental data collected capturing detailed performance parameters.•System simulations validated ...against multiple parameters and operating conditions.•Cavity receiver designed to maximize the total electric generation.•Peak receiver temperatures obtained from thermocouple measurements.
Higher performance cavity receivers are needed to increase the competitiveness of solar power plants. However, the design process needs to be improved with more relevant experimental and numerical analyses. Thereby, the performance of four different Dish-Stirling cavities is investigated experimentally analyzing the influence of the cavity aperture diameter and shape at various operating temperatures. Temperatures inside the cavity receiver were collected together with the electrical power produced by the engine-generator. Then, a thermal system simulation was modelled and a comprehensive multi-parameter and multi-operation validation was performed. To improve this validation, the temperature distribution across the receiver tubes was analyzed in order to relate temperatures on the irradiated region with the non-irradiated one, where thermocouples can measure. The simulations were later used to obtain cavity receiver efficiencies, temperatures and loss breakdowns. The results show that the cavity receiver must be studied in optimization processes in conjunction with the other system components. Moreover, the reverse-conical cavity was found to be more efficient than a nearly cylindrical shape. Regarding the cavity receiver thermal losses, radiation and natural convection present similar contributions in the system under study. Finally, it was found that thermocouples installed on a non-irradiated region can be used to obtain peak receiver temperatures if the measurements are rectified by a correction value proportional to the DNI.
In this study, the focus is on investigating prevalent issues of rupture and wrinkling that occur during the extra-deep drawing process. These defects are very common in a local sanitary equipment ...industrial company, mainly in the manufacture of bathtubs, which increases scrap and leads to loss of time and costs in production. To analyze these defects, a numerical simulation of the bathtub extra-deep drawing process was performed with industrial parameters. The originality lies in controlling non-uniform blank holder pressures generated from six actuators in order to control the flow of the blank between the blank holder and the die and ensure the production of defect-free bathtubs. 3D and ultrasonic thickness measurements were performed on a bathtub manufactured without defects. Numerical and experimental plots of the thickness reduction show that the two approaches are in good agreement. The numerical results demonstrate that there are no rupture or wrinkling defects in the bathtub final shape, which exactly matches the actual case manufactured by the company. The numerical analysis was also performed on different cases that can cause rupture and wrinkling defects, namely: the influence of the blank holder pressure, the blank initial shape, and the die design using draw beads.
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