ADAF Research Articles

Study on the dynamics of slip and detachment of thin de-icing fluid films on wing surfaces

Study on the dynamics of slip and detachment of thin de-icing fluid films on wing surfaces

Numerical study on the thermodynamic behavior of de-icing liquid droplets impacting walls

Spraying de-icing fluid is a key method to ensure the safe operation of aircraft in icy and snowy weather. The film aggregation and internal mixing of de-icing fluid droplets on the aircraft skin during a collision are crucial. Considering the rheological properties of the molecular viscosity change of the de-icing fluid droplets during the collision and the heat transfer model of the heat loss after the impact, the phase field method is used to capture the gas–liquid interface, and a thermal pressure/viscous coupling model is constructed. The thermodynamic behavior of different axial distances is calculated. The results show that, as the dimensionless axial distance of the droplet increases, the spreading length of the fused droplet decreases instead, and the heat transfer rate of the droplet increases with the increase in spreading length. After stabilizing, the increase or decrease in the heat transfer rate depends on the strength of the heat transfer between the liquid layers. As the dimensionless axial distance increases, the internal flow of the droplet weakens and, between the droplet and the wall, the heat flux density gradually decreases and the average temperature drop of the droplet becomes gradual.

The Effect of De-Icing Fluids on the Chemical Composition of Eluate in a Column Experiment with Sod–Podzolic Soil

The Effect of De-Icing Fluids on the Chemical Composition of Eluate in a Column Experiment with Sod–Podzolic Soil

THE EFFECT OF DE-ICING LIQUIDS ON THE CHEMICAL COMPOSITION OF ELUATE IN A COLUMN EXPERIMENT WITH SOD-PODZOLIC SOIL

The influence of the discharge of spent aircraft deicing fluid (ADF), utilized in civil aviation, on the chemical composition of the eluate of sod-podzolic soil was being studied in a column experiment. It was determined that Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn are released into the environment together with the ADF. It is also shown that the ADF leads to changes in the indicators of the composition of lysimetric waters such as СOD, pH, Eh, electrical conductivity, and heavy metal content. As a result of the ADF discharge, several elements, including Fe and Mn, become more mobile and migrate to the liquid phase, while others are fixed in the soil, resulting in the redistribution of elements in the soil profile.

Evaluation of aircraft deicing fluid as an external carbon source for denitrification

Water resource recovery facilities (WRRFs) performing biological nitrogen removal (BNR) often require external carbon sources for meeting nitrogen discharge permit limits. This brings an additional financial burden to the facilities considering the continuous need of these external carbon sources. This paper evaluates the utilization of airport stormwater, which in the winter season is rich in aircraft deicing fluid (ADF) as an alternative external carbon source. Denitrification and nitrification bench scale experiments were performed to assess the efficacy of external carbon sources to remove nitrogen in WRRFs. Experimental results showed that ADFs achieve denitrification rates of 0.064–0.066 d−1, higher than what achieved by a commercial carbon source, MicroC 2000A, with corresponding value of 0.058 d−1 at low temperatures, as low as 13 °C, which is considered a worst-case scenario for nitrogen removal efficiency. Furthermore, no inhibition to nitrification associated with the ADFs was observed. Subsequently a dynamic modeling study was conducted to assess the performance of ADFs as external carbon sources for denitrification and compared them to the conventional source that was being used in a full-scale BNR process. Results from the dynamic modeling study revealed that if 40 % of the spent-ADF at LaGuardia airport, New York City, could be collected with the stormwater and conveyed to a WRRF via the sewer collection system, an approximate reduction of 30 % of the commercial external carbon source could be accomplished by repurposing a waste product. This study contributes to the potential of ADF as a denitrification aid and an alternative for commercially available carbon sources with comparable nitrogen removal efficiencies.

Low-grade energy-bus air conditioning system using energy efficient three-fluid heat exchange terminals

Typical air conditioning terminals mainly focus on room temperature control, often neglecting adequate satisfactory room humidity management, resulting in poor thermal comfort. In addition, the direct heat exchange between refrigerant and air in these terminals cannot facilitate free-cooling using natural or waste cooling capacities. This study proposes a low-grade energy bus system that connects three-fluid heat exchange terminals, allowing for simultaneous control of room temperature and humidity. Furthermore, it enables the direct circulation of anti-icing fluid to each terminal for free cooling. Considering an office building in Nanjing, China, as an example, the annual operational performance of the proposed system is numerically studied and compared with two typical systems. The results reveal the following. 1) The three-fluid heat exchange terminals used can accurately regulate the room temperature and humidity, even when there are significant differences in the indoor cooling and dehumidification loads. 2) The annual system coefficient of performance (COP) of the proposed system increases from 3.3 to 3.9, leading to an annual energy saving rate of 14.4% compared to a typical water loop heat pump system in a typical office building in Nanjing, China. 3) Compared to commonly used room air conditioners, the proposed system is more energy-efficient.

Methyl and Ethyl Ethers of Glycerol as Potential Green Low-Melting Technical Fluids.

The study is dedicated to the consideration of lower alkyl ethers of glycerol as potential components of low-melting technical fluids (e.g., heat transfer fluids, hydraulic fluids, aircraft de-icing fluids, etc.). Four isomeric mixtures of glycerol ethers (GMME-monomethyl; GDME-dimethyl; GMEE-monoethyl; GDEE-diethyl) were synthesized from epichlorohydrin and methanol/ethanol in the presence of sodium and subjected to detailed characterization as pure compounds and as aqueous solutions (30-90 vol%). The temperature and concentration dependencies of density, viscosity, cloud point, boiling range, specific heat capacity, thermal conductivity, and rubber swelling were obtained. On the basis of the data obtained, a comparison was made between the aqueous solutions of glycerol ethers and of other common bases for low-melting liquids (glycerol, ethylene glycol, and propylene glycol). Pure glycerol ethers could potentially be used as technical fluids in a very wide temperature range-from -114 to 150 °C. It was further demonstrated that in low temperature applications (e.g., in low-temperature chiller systems) the glycerol-ether-based aqueous heat transfer fluids could provide enhanced efficiency when compared to the glycerol- or propylene-glycol-based ones due to their lower viscosities and favorable environmental properties.

Use of New Materials in the Manufacture of Containers to Store Anti-Icing Fluid at Civil Aviation Airfields

Use of New Materials in the Manufacture of Containers to Store Anti-Icing Fluid at Civil Aviation Airfields

Experimental investigation of heating performance of air source heat pump with stable heating capacity during defrosting

Traditional air source heat pumps with reverse defrosting and hot gas bypass defrosting methods significantly decrease the heating capacity and even extract heat from the user side, resulting in low indoor thermal comfort. In this study, an air source heat pump prototype was developed that used multiple air source heat exchangers linked with anti-icing fluid pipelines to extract heat from the outdoor air and alternately defrost one of the air source heat exchangers by transferring a small portion of the heat from the indoors, thus achieving stable heating to the user side during defrosting. Its performance was tested in an enthalpy difference chamber, and optimization was predicted based on the test results. The results showed that under the most severe frosting condition, with an outdoor temperature of 1 °C and a relative humidity of 95%, the heating capacity decay rate to the user side during defrosting was only 20%. After optimization, the heating capacity decay rate during defrosting could reach within 10%, and the coefficient of performance under nominal operating condition (outside temperature of −2 °C, supply water temperature of 35 °C) and the heating season performance factor were 3.38 and 4.05, respectively, when used for heating the radiation floor in hot summer and cold winter regions. The principles and results provided in this study can be applied to air source heat pumps with different heating capacity requirements during defrosting.

Efficacious degradation of ethylene glycol in baffled ozonation reactor in the presence of waste-derived MIL-53(Al/Fe)-metal-organic framework derived Al2O3/Fe3O4

Ethylene glycol (EG) has been widely used to produce polyethylene terephthalate (PET) bottles, antifreezes, and de-icing fluid. However, EG possesses toxic detrimental effects on human and aquatic creatures. The degradation of EG in catalytic ozonation based advanced oxidation processes was rarely reported before. In this regard, a novel porous catalyst, magnetic MIL-53(Al/Fe)-metal-organic framework (MOF) derived Al2O3/Fe3O4 (wAl-Fe@MOF) was synthesized for the first-time using PET, iron, and aluminum scraps for efficacious catalytic ozonation system (COS) of EG. A maximal EG degradation and mineralization of 97.03 ± 2.79% and 57.75 ± 2.60% were obtained in wAl-Fe-based COS, which was higher than sole O3 (70.76 ± 3.90%; 22.65 ± 2.20%) and O3/H2O2 (74.51 ± 2.58%; 36.57 ± 3.10%). The wAl-Fe@MOF displayed only about 18% drop in deterioration efficiency after 5th cycle of reusability, demonstrating outstanding stability and recyclability. The electron paramagnetic resonance and radical scavenging tests confirmed that surface adsorbed ˙OHads were majorly accountable for EG degradation. Phytotoxicity revealed that COS effectively reduced the toxicity of EG towards Vigna radiata. The energy consumption and operating cost were found to be 0.863 kWh m−3 order−1 and 0.086 $ m−3 order−1, indicating wAl-Fe@MOF based COS could be highly appropriate for wastewater purification in real field applications.

Development of a dynamic ice penetration model for runway de-icing products through performance experimental characterization

During winter, the clear runway concept is crucial to airports for maintaining passenger and employee safety. Research can optimize de-icing product application rates, thereby reducing costs and environmental impact. Currently, three aerospace standards exist for evaluating the performance of runway de-icing products. These comparative tests—ice melting, ice undercutting, and ice penetration tests—are carried out jointly in a systematic way and indicate whether a runway de-icing product is effective in actively reducing the presence of ice. Here we present a numerical model for the ice penetration method, for fluid runway de-icing product, with the goal of deepening the knowledge in this field. We apply a series of laboratory-based tests to measure the performance of runway de-icing products, and develop a new model to analyze the behavior of each product. The principal observation is that the product is more effective at 1 min and effectiveness decreases following an inverse logarithmic curve trend to 30 min. Through modeling, we observe that the dominant mode of heat transfer is natural laminar convection, and the model predicts a uniform melt length for the entire tube section. Thus, simplified ice penetration modeling using AS6211 can acceptably predict the rate of ice penetration as a function of time (mm/min), with the modeling confirmed by our experimental results. The future application of our simplified model to other existing de-icing fluid characterization test methods could identify the effects of diluted or undiluted solid runway de-icing products on ice penetration rates and ultimately on spreading rates.

Solar photodegradation of the UV filter benzotriazole in the presence of persulfate

Benzotriazole (BT), which is used as a UV filter, an anti-corrosion agent and anti-icing fluid, has been frequently observed in various water bodies. In this study, a sunlight/persulfate system was used to investigate BT degradation for the first time. The BT degradation behavior in the sunlight/persulfate system was well fitted by pseudo first-order kinetics. Compared to direct photolysis and persulfate oxidation, BT was significantly photodegraded by 90% within two hours in the presence of persulfate. The BT degradation rate was fastest under acidic conditions and slightly decreased at neutral pH 7. However, the BT degradation rate dramatically decreased under alkaline conditions (pH 9 and 11) due to the lower persulfate activation rates and deprotonated form of BT. Sulfate radicals (SO4·–), hydroxyl radicals (·OH), singlet oxygen (1O2), and superoxide radicals (O2–·) were identified via an electron paramagnetic resonance (EPR) spectrometer in the sunlight/persulfate system. SO4·– and·OH were the dominant species under acidic and neutral pH; 1O2 and O2–·contributed to only partial BT degradation under alkaline conditions. In addition, BT degradation was inhibited in the presence of common water matrix components (Cl–, HCO3–, NO3–, and dissolved organic matter) due to the scavenger effect and formation of less reactive radicals. Only slight mineralization occurred within 15 h of operation in the sunlight/persulfate system. This study comprehensively evaluated the BT degradation mechanism in a sunlight/persulfate system, and the results provide promising insight into the application of sunlight/persulfate systems in advanced water polishing treatment.

Advances in catalytic conversion of lignocellulosic biomass to ethylene glycol

ABSTRACT Ethylene glycol (EG) is an industrial chemical with multiple applications in polymers, anti-freeze agents, coolants, desiccants and de-icing fluids. It is prepared mainly from fossil feedstock resources. However, its manufacture from renewable sources like lignocellulosic biomass is attractive from the view points of carbon-neutrality and environmental benefits. A few industries have already ventured or committed to produce biomass-derived EG (bio-EG) on a pilot to demonstration scale. At present bio-EG is more expensive than the EG made from fossil resources. Advances are happening in developing more efficient and selective catalysts for the direct conversion of raw biomass and its hydrolysis products (cellulose and glucose) into bio-EG. This review presents the recent advances in catalysts for producing bio-EG.

Anti-icing fluid performance on substrates with different thermal conductivity and roughness

The performance of aircraft anti-icing fluids reduces unusually on aviation composites. It is unclear whether this is due to low substrate thermal conductivity or hydrophobicity. Therefore, we considered experimentally the performance of Newtonian and non-Newtonian aircraft anti-icing fluids on substrates with thermal conductivities from 0.17 to 252 W/m∙K. It was found that the decrease of substrate thermal conductivity promotes the freezing of Newtonian and low viscous Non-Newtonian fluids compared to the thicker Non-Newtonian one. The thermal conductivity effect can be explained by the competition of two heat transfer processes: heat accumulation and the transfer of latent heat. Thus, Newtonian and low viscous Non-Newtonian aircraft anti-icing fluids must be defined on aviation composites together with substrate thermal conductivity, wettability, and roughness.

Aircraft Anti-Icing Fluids Endurance Under Natural and Artificial Snow: a Comparative Study

The usage of De-Icing and Anti-Icing fluids is the most common method recognized to protect aircraft on the ground from freezing and frozen contaminants. The snow endurance times, which means the duration that a fluid can protect the vehicle from snow accumulations, is currently determined outdoor under natural conditions. To replace this expensive and very impractical method, the Anti-Icing Materials International Laboratory developed snow machine was used to perform a comparative study. In this first study, three commercial fluids were tested at various snow intensity rates under artificial snow generated with the snow machine in a cold chamber to validate the testing procedure and investigate the way forward. The results obtained were then positively compared to natural snow endurance times. They were also compared with natural snow regression curves, showing similar trends. This study demonstrated the great potential of this method showing the necessity of pursuing this investigation.

The physical properties of organic aircraft deicers under low temperature

Ethylene glycol (EG) deicer and propylene glycol (PG) deicer were frequently used as the aircraft de-icing fluids in cold region. In this paper, the icing pressure (Ip), icing volume expansion rate (ΔVP), freezing point (T0) and under-cooling (△T) of aircraft deicers with different concentrations were investigated, and the above indicators of aircraft deicers were also compared with that of water and NaCl deicers. The results showed that the icing volume expansion of deicers was the direct cause of icing pressure. During the cooling process, values of Ip and ΔVP firstly increased sharply, then slowly, and finally became stable. The stabilized values of Ip and ΔVP decreased with concentration. The stabilized Ip value of EG deicer was slightly higher than that of 3.5% NaCl deicer and far greater than 3.5% PG deicer. Of all the tested deicers, the stabilized ΔVP value of NaCl deicer was the highest and that value of EG deicer was close to that of PG deicer. The results further confirmed the feasibility of using impulse of icing pressure as the indicator to evaluate the freeze-thaw deterioration to concrete.

Assessment of influence of anti-icing fluids based on ethylene and propylene glycol on environment and airport infrastructure

Assessment of influence of anti-icing fluids based on ethylene and propylene glycol on environment and airport infrastructure

Assessment of influence of anti-icing fluids based on ethylene and propylene glycol on environment and airport infrastructure

Assessment of influence of anti-icing fluids based on ethylene and propylene glycol on environment and airport infrastructure

Ice imaging in aircraft anti-icing fluid films using polarized light

During qualification endurance tests of aircraft de−/anti-icing fluids, their failure is evaluated by a naked-eye visual inspection and occasionally poking freezing areas with a toothpick. For ice detection improvement, image processing techniques have been developed in the visible and infrared spectra. Such techniques have issues with low ice contrast or combining with the visual inspection. Here we show how to enhance ice contrast in the visible spectrum by using ice birefringence and polarized light reflection. The method can be used for both visual inspection and automatic ice detection systems.

Anti-icing fluids interaction with surfaces: Ice protection and wettability change

Some aircraft anti-icing fluids can dangerously weaken on hydrophobic surfaces. However, information about such fluids and surfaces was not full. Therefore, we considered the interaction of commercially available Newtonian and pseudo-plastic anti-icing fluids with super-hydrophilic and hydrophobic aluminum surfaces. In freezing rain simulations, no noticeable surface effect was observed on fluid endurance times at 10% ice coverage of the surfaces. The difference with previous works can be caused by fluid surface tensions, the contact angle hysteresis of test plates, and fluid viscosity (the last is irrelevant for Newtonian fluids). In further comparative studies, the roughness must also be considered because on rough hydrophobic surfaces the Newtonian fluid took longer to freeze once ice coverage surpassed 20% compared to smooth super-hydrophilic surfaces. Furthermore, the fluid physical adsorption in the surface texture leads to the drifting of receding contact angles of water on hydrophobic surfaces, thereby worsening their water-repelling. Thus, smooth hydrophobic surfaces are probably the preferred solution for ice mitigation systems contacting aircraft anti-icing fluids.