Purification of spent deicing fluid by membrane techniques

Membrane-based concept comprising microfiltration and nanofiltration pre-treatments, reverse osmosis pre-concentration, and membrane distillation used for final concentration was applied for producing purified and concentrated recycled deicing fluid. Additionally, a techno-economic assessment was conducted to determine the economic viability of the recycling concept. By a straightforward membrane-based concept, ∼95% of solid and colloidal impurities together with certain deicing fluid additives such as colorants and surfactants could be efficiently removed (removal efficiencies of ∼90% and ∼93%, respectively), and resulting purified deicing fluid could be concentrated to ∼60 wt% glycol solution, enabling its recycling in deicing operations. Preliminary techno-economic assessment indicated that a membrane-based concept can be used as an economically viable alternative for recycling the spent deicing fluid at airports. The techno-economic case study at an airport consuming 4,000 tonnes of deicing fluid during 6 months annually showed the concept to be economically feasible when the price of purchased propylene glycol is over 1,000 EUR/tonne. In addition to the purchase price of the propylene glycol, the most important cost factors were labor cost and the annual consumption of deicing fluid. Integrating the membrane concept with other operations at airport has potential to decrease the labor cost and further improve the economic feasibility of the concept.

CFD Model for Aircraft Ground Deicing: Verification and Validation of an Extended Enthalpy-Porosity Technique in Particulate Two Phase Flows

Researchers have focused in the last five years on modelling the aircraft ground deicing process using CFD (computational fluid dynamics) in order to reduce its costs and pollution. As preliminary efforts, those studies did not model the ice melting nor the diffusion between deicing fluids and water resulting from the melting process. This paper proposes a CFD method to simulate this process filling these gaps. A particulate two-phase flow approach is used to model the spray impact on ice near the contaminated surface. Ice melting is modelled using an extended version of the enthalpy-porosity technique. The water resulting from the melting process is diffused into the deicing fluid forming a single-phase film. This paper presents a new model of the process. The model is verified and validated through three steps. (i) verification of the species transport. (ii) validation of the transient temperature field of a mixture. (iii) validation of the convective heat transfer of an impinging spray. The permeability coefficient of the enthalpy-porosity technique is then calibrated. The proposed model proved to be a suitable candidate for a parametric study of the aircraft ground deicing process. On the validation test cases, the precision of heat transfer prediction exceeds 88%. The model has the ability of predicting the deicing time and the deicing fluid quantities needed to decontaminate a surface.

The Air in the Cabin of Passenger Aircraft Is Not as Good As Is Often Assumed - Backgrounds, Possible Solutions and Their Implementation

Fume or smoke events have already been observed on many flights of large passenger aircraft. These events can be explained by sudden failures of seals on the bearings of jet engines, which results in pyrolized engine oil to reach the passenger cabin. But there are also many other ways in which cabin air can be contaminated. Contamination can also be caused by hydraulic or deicing fluid. Pilots, cabin crew and passengers have become ill from such singular events as they themselves report and as confirmed by medical professionals. But even without having ever experienced such a single event, pilots and cabin crew have fallen ill. This could be explained by the small amounts of oil that regularly leak from the seals.

Influence of Geometrical Parameters on Heat Transfer of Transversely Corrugated Helically Coiled Tube for Deicing Fluid

In order to ensure flight safety in cold winter, aircraft ground deicing is crucial and necessary. In Chinese deicing fluid heating system, the helically coiled tube is paramount exchanger to heat deicing fluid. The deicing fluid is ethylene-glycol-based mixture with high viscosity. Aiming at heat transfer enhancement of deicing fluid, ring rib is formed by an embossed tube wall toward the internal of the tube; thus, transversely corrugated helically coiled tube (TCHC) is achieved. Depth and width are two key geometrical parameters of ring rib. Based on field synergy principle, the influence of depth–diameter ratio (H/D) and width-diameter ratio (w/D) is investigated through numerical simulation. The results show that outlet temperature, mean convection heat transfer coefficient, and Nusselt number have similar trends, which first increase and then decrease nonlinearly. The variation of flow resistance coefficient is inversely proportional to Reynolds number. Especially, the effect of H/D is more significant than that of w/D. Field synergy angle and velocity field are also analyzed to reveal the mechanism of heat transfer. TCHC performs better than the original tube. Orthogonal experiment calculates the outlet temperature of TCHC when H/D and w/D change. The combination of H/D=0.075 and w/D=0.5 is best solution. TCHC effectively enhances heat transfer of deicing fluid. Therefore, TCHC is beneficial to improve the deicing efficiency and ensure the flight punctuality.

Corrosion electrochemical behavior of cadmium-plated 4340 steel in aircraft landing gears under thin electrolyte layers of potassium acetate deicing fluid

We present a study of the corrosion behavior of cadmium-plated 4340 steel in aircraft landing gears under thin electrolyte layers of potassium acetate deicing fluid.

Research on the Heating of Deicing Fluid in a New Reshaped Coiled Tube

Aircraft ground deicing operation is significant to ensure civil flight safety in winter. Helically coiled tube is the important heat exchanger in Chinese deicing fluid heating system. In order to improve the deicing efficiency, the research focuses on heat transfer enhancement of deicing fluid in the tube. Based on the field synergy principle, a new reshaped tube (TCHC) is designed by ring-rib convex on the inner wall. Deicing fluid is high viscosity ethylene-glycol-based mixture. Because of the power function relation between high viscosity and temperature, viscosity has a negative influence on heat transfer. The number of ring-ribs and inlet velocity are two key parameters to the heat transfer performance. For both water and ethylene glycol, the outlet temperature rises when the number of ring-ribs increases to a certain limit. However, the increasing of velocity reduces heating time, which results in lower outlet temperature. The heating experiment of the original tube is conducted. The error between experiment and simulation is less than 5%. The outlet temperature of TCHC increases by 3.76%. As a result, TCHC efficiently promotes the coordination of velocity and temperature fields by changing the velocity field. TCHC has enhanced heat transfer of high viscosity deicing fluid.