The purpose of this paper is to present and analyse the decision-making problem faced by a future house owner - selection of the optimal solution of building thermal insulation in relation to the selected criteria, both related to costs and future benefits. The problem of selecting the best solutions in the construction sector is widely discussed in the science literature. In this paper, the authors decided to solve the raised problem by using the Entropy method.
In the authors’ opinion, the issue of incorrectly functioning water insulation of foundation walls in the existing buildings in Poland is currently rather common. The paper includes a multicriteria analysis aimed at arranging the selected options of the foundation wall vertical water insulation technology in an existing model historic building using the weighted sum, entropy and AHP methods. Each of the studied solutions was evaluated in terms of the following criteria: costs of construction works, time of execution of construction works, popularity of using particular insulation options by other contractors, durability of the executed insulation and the degree of nuisance of the executed works
Before disassemble and demolition of five granulation towers the authors planned and carried out measurements of the intensity of vibrations induced during the fall of the dismantled components of towers on the ground. The main aim of the study was to determine the maximum permissible weight of falling elements of the towers during the demolition, in terms of ensuring the protection of buildings and equipment located in the vicinity of the works. It was unacceptable to increase the vibration amplitude displacement in each section of measurement on each of the three perpendicular axes by more than 2 μm peak-to-peak value and the absolute velocity of RMS of vibration amplitude couldn’t be increased by more than 1 mm/sec value than the background vibration during the demolition of the towers. Preliminary experimental studies were conducted on a test stand and the measurements were made on the real object. The amplitudes of vibration waves displacement and velocity were recorded on the measurement section in the direction of the protected building. The results of measurements were used to identify the propagation of the shock wave and the effectiveness of the proposed insulation layers.
Additional sound sources are used as actuators in the vast majority of active noise reduction systems. One of the possible opportunities to extend the field of applications of active noise reduction systems is using active structures of variable sound insulation. The paper presents an analysis of ways of reducing noise with a structure of variable sound insulation consisting of a metal plate, active elements (Macro Fiber Composite), and a control system. The paper presents results of acoustic radiation simulations and measurements of sound intensity generated by the structure under the influence of stimulation by an acoustic wave. Simulations of mechanical vibrations and acoustic radiation for the plate were performed with the finite element method and ANSYS software. Simulation results made it possible to select locations for gluing the active elements and sensors. Analyses of the sound pressure level in the space to which the plate is radiating made it possible to determine dominant frequencies in the characteristics and, as a result, indicate vibration modes that can be reduced. Sound intensity measurements were performed with a three-way probe of USP mini Microflown. Results of simulations and measurements show that it is possible to achieve an improvement of the insulating power of a metal plate by approx. 10 dB.
A verification study of ultrasound transmission numerical simulation results with experiment results is presented in this paper. The work considers a model of a transformer tank which is filled with electro insulating oil. In the experiment, performed under laboratory conditions, an ultrasound wave is generated by a piezoelectric transducer that is fixed in the centre of the tank and measured by another transducer mounted inside the tank at three distances: 10, 20 and 30 cm from the sound source. The transducer is able to measure and generate acoustic waves in the ultrasound frequency band up to 1 MHz. The simulation considers numerical calculation of acoustic pressure distribution inside the tank in which acoustic source emits waves with frequency equal to 100 kHz. Verification analysis has confirmed consistency of the numerically calculated values with the measurement results.
The article presents the results of diagnostic measurements of partial discharge signal propagation from the winding insulation in electrical machinery, which were performed using an on-line method. This paper describes the results of experiments and the acquired experience in the monitoring of winding insulation in high power and high voltage electrical machines which are important in industrial production processes. The authors show the measurement techniques employed in their research. Representative measurement results are presented along with their analysis. The authors use an SKF monitoring systems to measure: vibrations, temperature, and humidity, as major factors affecting partial discharge activity in the from winding insulation of electrical machines.
A commercially available ASPEN PLUS simulation using a pipe model was employed to determine the maximum safe pipeline distances to subsequent booster stations as a function of carbon dioxide (CO2) inlet pressure, ambient temperature and ground level heat flux parameters under three conditions: isothermal, adiabatic and with account of heat transfer. In the paper, the CO2working area was assumed to be either in the liquid or in the supercritical state and results for these two states were compared. The following power station data were used: a 900 MW pulverized coal-fired power plant with 90% of CO2recovered (156.43 kg/s) and the monothanolamine absorption method for separating CO2from flue gases. The results show that a subcooled liquid transport maximizes energy efficiency and minimizes the cost of CO2transport over long distances under isothermal, adiabatic and heat transfer conditions. After CO2is compressed and boosted to above 9 MPa, its temperature is usually higher than ambient temperature. The thermal insulation layer slows down the CO2temperature decrease process, increasing the pressure drop in the pipeline. Therefore in Poland, considering the atmospheric conditions, the thermal insulation layer should not be laid on the external surface of the pipeline.
The results from the experimental research are presented in the abstract. The experimental research involved utilization of the sludge from the mine water treatment plant of Coal Quarry ČSA/Czechoslovak Army/ (hereinafter “ČSA”) and Coal Quarry Jana Švermy (hereinafter “JŠ”) in the segment of thermal insulation mortars. The mine water treatment is described below including chemical and mineralogical sludge composition as the additional component of the binding material in the polyurethane thermal insulation mortars. Furthermore the composition of experimental mixtures of the thermal insulation polyurethane mortar is presented in the work and its physical-mechanical properties. The monitored elements included the strength characteristics, heat conductivity coefficient λ, and water vapour diffusion coefficient μ.
In this study, agar-based nanocomposite films containing ultra-porous silica aerogel particles were fabricated by gel casting using an aqueous agar/silica aerogel slurry. The silica aerogel particles did not show significant agglomeration and were homogeneously distributed in the agar matrix. Transmission electron microscopy observations demonstrated that the silica aerogel particles had a mesoporous microstructure and their pores were not incorporated into the agar polymer molecules. The thermal conductivities of the agar and agar/5 wt.% silica aerogel nanocomposite films were 0.36 and 0.20 W·m–1·K–1, respectively. The transmittance of the agar films did not decrease upon the addition of silica aerogel particles into them. This can be attributed to the anti-reflection effect of silica aerogel particles.
The main problem in the measurement of airborne sound insulation is the measurement of the sound power radiated by the barrier, in practice performed by measuring the sound pressure level and the acoustic absorption in the receiving room. Large variations of the sound pressure level in a reverberation room indicate the presence of dominating strong standing waves, so that it becomes necessary to install diffusing elements. In ISO 10140, the limits have been defined in which the reverberation time at frequencies at and above 100 Hz should be included. Sometimes, however, in the case of rooms with a large volume, obtaining the required parameters is difficult and sometimes even impossible. It should then be checked whether the measured sound insulation depends on the reverberation time.
The paper presents the results of sound insulation measurements at various reverberation time lengths in subsequent stages of diffusing elements installation in the receiving room. An analysis of diffusing materials amount and arrangement influence on the uniformity of the sound pressure level distribution and reverberation time in the room as well as the value of the measured sound insulation was carried out. Uncertainty of sound insulation measurement with partial uncertainties was adopted as a criterion supporting the assessment of the obtained results.
Extensive efforts have been made for many years by the power generating industry to replace conventional solid and liquid insulation with synthetic materials. Those measures are aimed at increasing the load capacity, improved fire safety and extending transformer life during exploitation. Modern insulating materials include aramid fibre-based paper and insulating fluids made of synthetic and natural esters. The paper presents research results of the electrostatic charging tendency (ECT) of mixtures of fresh and aged mineral oil Trafo En with synthetic ester Midel 7131 and natural ester Midel 1204. The measurements were taken in a flow-through system using the pipes made of metal, cellulose and aramid paper. The influence of the liquid flow velocity, the type of material of the measuring pipe and the mixture content on the level of the streaming electrification current generation was determined.
This paper describes preparation methodology and research results of newly developed materials from post-production fibrous waste that are resistant to high temperatures. Widely available raw materials were used for this purpose. Such approach has significant impact on the technological feasibility and preparation costs. Obtained materials were verified via applying of various tests including characterization of shrinkage, porosity, density and water absorption as well as X-ray analysis (XRD), followed by mechanical bending and compressive strength determination.
Based on the research results, the possible applications of materials as thermal insulators were indicated.
The modern cabin of heavy duty machines have to fulfil a number of requirements which deal with operators' work comfort. More and more often, the vibroacoustic and thermal comforts decide about the cabin quality. This paper presents principles of acoustic and thermal calculations as well as their use in combined assessment.