Search Results (11)

Ice accumulation on heating, ventilation, air conditioning, and refrigeration (HVACR) structures presents significant operational challenges. These challenges include reduced efficiency, increased energy consumption, and potential damage to equipment. Traditional de-icing methods, such as chemical treatments, mechanical scraping, or heating-based techniques, are often labor-intensive, costly, and environmentally harmful. This study uniquely investigates ultrasonic de-icing as an energy-efficient alternative for HVACR applications, focusing on the specific structural geometries found in these systems. A comprehensive numerical simulation framework was developed using finite element analysis to explore ultrasonic wave propagation across four distinct HVACR structures. Key parameters such as ultrasonic frequency, power levels, and the number and placement of actuators were examined for their impact on ice detachment efficiency. Results from simulations on a plate structure reveal that ultrasonic excitation can propagate effectively across large areas (at least 150 × 150 mm), enhancing the de-icing coverage. Lower frequency (e.g., 30 to 45 kHz) excitation results in greater displacement, improving de-icing performance, while increased actuator numbers with the same total power input also enhance effectiveness. Two actuators seem sufficient for the de-icing of a 300 × 300 mm plate. For tube-and-fin structures, specific high-power ultrasonic frequencies selectively excite the fin plates, demonstrating efficient ice removal when actuated on the tube. However, optimal performance requires careful design of actuator placement and vibration modes to accommodate the irregular shapes of these structures. Full article

This study examines the verification of the mechanical properties of ordinary concrete with Portland cement (OPC) and high-performance concretes (HPCs) after exposure to the effects of varying temperatures, in addition to durability tests as part of the experimental testing. Particular emphasis is placed on the comparison between OPC and HPC. Before describing the behavior of concrete under the influence of heat and the difference between ordinary and high-performance concrete, the microstructures of both hardened mixtures were monitored, and the chemical compounds of the used Portland cement and silica fume were analyzed using a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). For the experiments, compressive strength and flexural strength tests were performed before and after stressing at elevated temperatures. Furthermore, the experiments included the following: a study of concrete color changes under the influence of elevated temperatures, the use of the ultrasonic pulse method, the determination of resistance to water and chemical de-icing agents, and an examination of the frost resistance of concrete. This study considers the differences between the two concretes—OPC and HPC—especially in terms of their mechanical properties, as well as their durability and resistance to chemicals. This research contributes to the understanding of the properties of the two types of concrete; subsequently, it can help in the selection of concrete for specific applications. Full article

Recent growth in materials science and engineering technologies has pushed the construction industry to engage in new applications, such as the manufacturing of smart and electrically conductive products. Such novel uses of conductive construction materials would potentially allow their use in conjunction with various fields, such as those referred to as “Industry 4.0.” The following study uses iron oxide (Fe₃O₄)-multi-walled carbon nanotubes (MWCNTs) nanocomposites synthesized by chemical vapor deposition (CVD) and incorporated into the cementitious mortars as a substitute for sand at 1, 2, and 3% ratios to enhance the electrical conductivity. Results reveal that the electrical resistivity of cementitious composites decreases (due to the increase in electrical conductivity) from 208.3 to 61.6 Ω·m with both the Fe₃O₄-MWCNTs nanocomposites ratio and the increasing voltage. The lowest compressive strengths at 7 and 28 days are 12.6 and 17.4 MPa for specimens with 3% Fe₃O₄-MWCNTs and meet the standards that comply with most applications. On the other hand, the highest porosity was reached at 26.8% with a Fe₃O₄-MWCNTs rate of 3%. This increase in porosity caused a decrease in both the dry unit weight and ultrasonic pulse velocity (from 5156 to 4361 m/s). Further, it is found that the incorporation of Fe₃O₄-MWCNT nanocomposites can have a negative effect on the hardening process of mortars, leading to localized air cavities and an inhomogeneous development of cementing products. Nonetheless, the improvement of the electrical conductivity of the samples without significantly compromising their physico-mechanical properties will allow their use in various fields, such as deicing applications with low-voltage electric current. Full article

The coupled resonance mechanism of interface stratification of thin coating structures excited by horizontal shear waves is investigated by the forced vibration solution derived from the global matrix method, the integral transformation method, and the plane wave perturbation method. The interface shear stress reaches the peak at coupling resonance frequencies which are an inherent property of the structure, and decreases with the increase of coating thickness or the increase of shear wave velocity difference between the substrate and coating. At the coupling resonance frequency, the thin coating structure is more easily stratified at the interface. The result could provide a theoretical basis for the popularization and application of ultrasonic deicing/defrosting/de-accretion technology. Full article

Icings on moving machinery, such as wind turbines and aircraft wings, degrade their performance and safety. Ultrasonic vibration is considered one of the deicing methods. In this research, simulations and experiments are carried out to explore the effect of ultrasonic vibration on the adhesive characteristic of ice on aluminum alloy plates. Harmonic response analyses are conducted to analyze the changing and distributions of shear stresses at the adhesive interface under different frequencies and sizes of PZT patches. The results show that there is optimum side length and thickness of the PZT patch, as the size of the iced aluminum alloy plate is constant. In these conditions, the shear stresses at the adhesive interface are high. Then, experiments on adhesive torque of ice are carried out to calculate the adhesive shear stresses of ice. The results show that the adhesive force of ice decreases under the excitation of ultrasonic vibration. When the excited frequency is 79 kHz, the adhesive torsional shear stress is 0.014 MPa, which is only 7% of the one with no ultrasonic vibration. Full article

In cold and humid regions, ice accretion sometimes develops on the blades of wind turbines. Blade icing reduces the power generation of the wind turbine and affects the safe operation of the wind farm. For this paper, ultrasonic micro-vibration was researched as an effective de-icing method to remove ice from the wind turbine blade surface and improve the efficiency of wind turbine power generation. A blade segment with NACA0018 airfoil and the hollow structure at the leading edge was designed. The modal analysis of the blade was simulated by ANSYS, and the de-icing vibration mode was selected. Based on the simulation results, the blade segment sample with PZT patches was machined, and its natural frequencies were measured with an impedance analyzer. A return-flow icing wind tunnel system, and a device used to measure the adhesive strength of ice covering the airfoil blade, were designed and manufactured. The experiments on the adhesive strength of the ice were carried out under the excitation of the ultrasonic vibration. The experimental results show that the adhesive strength of the ice, which was generated under the dynamic flow field condition, was lower than the ice generated by water under the static flow field condition. Under the excitation of the ultrasonic vibration, the adhesive strength of the ice decreased. When the excitation frequency was 21.228 kHz, the adhesive strength was the lowest, which was 0.084 MPa. These research findings lay the theoretical and experimental foundations for researching in-depth the application of the ultrasonic de-icing technology to wind turbines. Full article

An aggressive impact of the formed ice on the surface of man-made objects can ultimately lead to serious consequences in their work. When icing occurs, the quality and characteristics of equipment, instruments, and building structures deteriorate, which affects the durability of their use. Delays in the adoption of measures against icing endanger the safety of air travel and road traffic. Various methods have been developed to combat de-icing, such as mechanical de-icing, the use of salts, the application of a hydrophobic coating to the surfaces, ultrasonic treatment and electric heating. In this review, we summarize the recent advances in the field of anti-icing and analyze the role of various additives and their operating mechanisms. Full article

The review reflects physical solutions for de-icing, one of the main problems that impedes the efficient use of wind turbines for autonomous energy resources in cold regions. This topic is currently very relevant for ensuring the dynamic development of wind energy in the Arctic. The review discusses an effective anti-icing strategy for wind turbine blades, including various passive and active physical de-icing techniques using superhydrophobic coatings, thermal heaters, ultrasonic and vibration devices, operating control to determine the optimal methods and their combinations. After a brief description of the active methods, the energy consumption required for their realization is estimated. Passive methods do not involve extra costs, so the review focuses on the most promising solutions with superhydrophobic coatings. Among them, special attention is paid to plastic coatings with a lithographic method of applying micro and nanostructures. This review is of interest to researchers who develop new effective solutions for protection against icing, in particular, when choosing systems for protecting wind turbines. Full article

High-density polyethylene (HDPE) above-ground storage tanks (AST) are used by highway agencies to store liquid deicing chemicals for the purpose of road maintenance in the winter. A sudden AST failure can cause significant economic and environmental impacts. While ASTs are routinely inspected to identify signs of aging and damage, current methods may not adequately capture all defects, particularly if they are subsurface or too small to be seen during visual inspection. Therefore, to improve the ability to identify potential durability issues with HDPE ASTs, additional non-destructive evaluation (NDE) techniques need to be considered and assessed for applicability. Specifically, this study investigates the efficiency of using infrared thermography (IRT) as a rapid method to simultaneously examine large areas of the tank exterior, which will be followed by closer inspections with conventional and phased array ultrasonic testing (UT) methods. Results show that IRT can help to detect defects that are shallow, specifically located within half of the tank’s wall thickness from the surface. UT has the ability to detect all defects at any depth. Moreover, phased array UT helps to identify stacked defects and characterize each defect more precisely than IRT. Full article

An effective deicing system is needed to be designed to conveniently remove ice from the surfaces of structures. In this paper, an ultrasonic deicing system for different configurations was estimated and verified based on finite element simulations. The research focused on deicing efficiency factor (DEF) discussions, prediction, and validations. Firstly, seven different configurations of Lead zirconate titanate (PZT) disk actuators with the same volume but different radius and thickness were adopted to conduct harmonic analysis. The effects of PZT shape on shear stresses and optimal frequencies were obtained. Simultaneously, the average shear stresses at the ice/substrate interface and total energy density needed for deicing were calculated. Then, a coefficient named deicing efficiency factor (DEF) was proposed to estimate deicing efficiency. Based on these results, the optimized configuration and deicing frequency are given. Furthermore, four different icing cases for the optimize configuration were studied to further verify the rationality of DEF. The effects of shear stress distributions on deicing efficiency were also analyzed. At same time, a cohesive zone model (CZM) was introduced to describe interface behavior of the plate and ice layer. Standard-explicit co-simulation was utilized to model the wave propagation and ice layer delamination process. Finally, the deicing experiments were carried out to validate the feasibility and correctness of the deicing system. Full article

Ultrasonic de-icing is a promising method to de-ice structures by using lightweight and simple transducers, with the advantage of low power consumption. A successful ultrasonic de-icing technique requires the understanding of the effects of different parameters on de-icing. This paper presents a thorough parametric study of the ultrasonic de-icing method on a plate with coating. First, the dispersion equations of shear horizontal (SH) and Lamb waves were derived based on the global matrix method. Meanwhile, interface shear concentration coefficients (ISCC) were introduced to represent the ability of ultrasonic de-icing, which was further integrated into Lamb wave and SH waves dispersion curves for the selection of optimal frequencies. Second, a three-layer plate model (host plate-coating-ice) was used to demonstrate the effect of different parameters of coating and the thickness of ice on ultrasonic de-icing. The theoretical model provided the design principle of coating and ultrasonic parameters required for efficient de-icing. Finally, an experiment was conducted on an ultrasonic de-icing platform to validate the proposed ultrasonic de-icing method. In this process, material parameters including the Young’s modulus, thickness of coating, and thickness of the ice layer were analyzed. The trends of power consumption and optimal frequency of experiments are in good agreement with the analytical calculated results. Full article