Papers by Keyword: Fouling

Abstract: There is a need for solutions to provide sufficient cooling from power devices, which produce large amounts of heat. This paper focuses on the influence of design of bifurcated fluid streams to dissipate heat. In this study, a single Y-tubes, a double Y-tubes, and an X-tubes designs are studied numerically under space constraints. For a comprehensive and in-depth performance analysis, both heat dissipation and hydraulic performances are analyzed. The distributions of velocity and temperature in the fluid streams is simulated, also the flow resistances and dissipated heat are calculated. Based on the results obtained, a thermo-hydraulic performance factor is introduced for the designs under study. In addition, the accumulation of undesired substances on the wall surface (fouling) that may influence the heat exchanging capability is studied.

Abstract: The studies to establish the species composition of micro-mycetes inhabiting the surface of cement composites after aging in sea water have been carried out. Cement stone made on the basis of Portland cement clinker, a mineral additive and a fungicidal preparation was considered as the studied material. To determine the materials’ fouling by microorganisms, their species composition, imprints and sampling methods were used. A change in the species composition of mycobiota isolated from the cement composites’ surface modified with sodium sulfate and sodium fluoride depending on the amount of active filler, gypsum, and biocidal additives was experimentally revealed. The effectiveness of using the biocidal cement composites with an active mineral additive has been confirmed. It was found that the composites on the developed compositions showed higher resistance compared to the materials on ordinary cement. The compositions modified with biocidal additives showed a fungicidal effect.

Abstract: Titania pillared clay membranes exhibit unique charge characteristics which are dependent on the solution pH. Doping of such membranes with precious metal like Pt induces a positive charge on the surface of the membranes, thus increasing its resistance against fouling. X-ray Diffraction (XRD) and Fourier Transform Infra-Red Spectroscopy (FT-IR) confirm the complete intercalation of anatase titania in the interlayer spaces of Montmorillonite in the present work. These membranes efficiently removed 83% of the dye from the real textile effluent in a one filtration cycle.

Abstract: Natural Organic Matter (NOM) content in peat water is a major problem of membrane fouling in ultrafiltration (UF). For that, two stages adsorption as pre-treatment was employed to minimize the membrane fouling of NOM content. This research was carried out to investigate the effect of two stages adsorption on ultrafiltration performance for NOM removal that remains in peat water. This method was using powdered activated carbon (PAC) dosage of 80, 160, 240, 320, 400, 480, 560, 640, 720, 800, 880 dan 960 mg.L^-1. Then, Polysulfone (Psf) material was employed for Ultra filtration process. Membrane was applied in a dead-end mode with various operating pressure (1; 1.5; 2; 2.5; 3 bar). As a results, the optimum dose of PAC was 800 mg L-1 with dosage ratio of 3/4:1/4. Two stages adsorption-UF PSf provided the range from 86.9 to 92.8% of KMnO₄ and 74.1-88.1% of UV₂₅₄. For the experimental condition of 3 bar, the highest flux was achieved up to 39.919 L h^-1.m^-2.

Abstract: This work experimentally explored the influence of nano-fouling, and it was also compared and analyzed CHF, flow boiling heat transfer coefficient, contact angle, and surface roughness. The working fluids in this study were used as purewater and a 0.01 vol% oxidized MWCNT nanofluid. The flow velocity conditions are established at 0.5, 1.0, and 1.5 m/s. Also, the nanoparticles of oxidized graphene were deposited on a heat transfer surface, and artificial spray coating times for nano-fouling are established at 0, 120, 180, and 240 sec. As the results, it was found that the superheated temperature to the CHF extremely increased in case of nano-fouling, it is caused by physical damage of heat transfer system. The flow boiling heat transfer coefficient in an oxidized graphene nanofluid increased up to 24.29% without any treatment on the heat transfer surface, but the coefficient in case of nano-fouling decreased down to 16.26% more than in the purewater.

Abstract: This study aimed to investigate the effects of hydroxyapatite integration with polyethersulfone (PES) membrane towards fouling mitigation. PES membrane were modified through self- assembly technique with hydroxyapatite (form fish sclaes) which prepared at different sintering temperatures. This composite membrane were characterized concerning on permeability coefficient, membrane porosity, ATR-FTIR analysis fouling quantification. Overall results showed that PES membrane incorporated with hydroxyapatite sintered at 300°C (PES/FSHAp-300) promoted an excellent characteristics and performance. The membrane demonstrated high permeability coefficient and membrane porosity for about 93.52 L/m².h and 89.78%, respectively. This kind of membrane was also presented the highest flux recovery ratio around 83.3% and this findings can be a good pathway for the design of low fouling membrane for enzyme separation.

Abstract: On-line cleaning of heat exchangers operating in a heat exchanger network (HEN) is aimed at preventing unnecessary losses of energy that can be recovered in HEN. If time behaviour of fouling in each heat exchanger can be estimated on the basis of past experience, then the optimal schedule of cleaning interventions can be determined by maximizing the objective function expressing the economic value of avoidable reduction in the energy recovery [1]. The crucial assumption for the presented paper is that on-line measurements of the mass flow and inlet and outlet temperature are available for each process stream. That made possible to evaluate fouling-induced reduction in the recovered energy flow using neural network model of HEN based on the measurements. The neural network (NN) model of HEN was applied in diagnostics of deposits influence on heat recovery in HEN by taking into account the time behaviour of fouling approximated by NN. The application of a neural network to the evaluation of changes in the energy flow recovered in a HEN has been tested using a simulated heat exchanger network as a reference. The simulation of HEN (implemented in MATLAB software) was based on a dynamic HEN model employing heat exchanger decomposition into interconnected cells whose overall dynamic behaviour is described by an array of lumped-parameter models. Computational aspects of the approach outlined above were studied on the example of a HEN featuring 26 process streams and 31 heat exchangers, operating in a crude distillation unit of 440 t/h processing capacity. A diagnostics of deposits influence on heat recovery in HEN makes it possible to attain a saving of about 5% of recoverable energy with the annual value of about 0,86 million USD.

Abstract: Water pollution comprises all of those compounds that change the quality of groundwater and surface water, therefore reducing the suitability of natural water for human use and other vital processes. These compounds result from human activities, especially those that are industrial, agricultural and domestic.The polyamide thin film composite reverse osmosis membranes become important in desalination of sea water and brackish water or waste water. However the polyamide reverse osmosis membranes tend to fouling due to their hydrophobic and rough surfaces. In this study flux and rejection of waste water from aluminum production industry were obtained during filtration process by using modified commercial composite membranes. Amount of fouling was evaluated with unmodified and modified membranes. Rejection of iron particles and PH of feed and permeate solutions were determined after filtration process. Results shows that modified membranes were performed higher metal ion rejection and antifouling performance than unmodified membranes.

Abstract: According to the mechanism of thermal system modelling method, the implanting the health factors is adopted, the steady state non-1inear performance deterioration model is founded by integrating experience performance with thermodynamics theory. Considering the low-pressure compressor suffer from fouling, the performance deterioration of gas turbine is simulated based on the temperature-control of outlet of combustion chamber. The measurement parameters of variation are obtained; the mechanism and sensitivity of the change are defined. The results illustrate that the outlet pressure of the low-pressure compressor is degenerated obviously, so can be well-monitor sensors. The deterioration of low-pressure shaft speed is strong non-1inear decreased vs. the fouling increased. Thanks to the cooling for air of outlet of low-pressure compressor by intercooler, in conjunction with the power decreased of low-pressure turbine, the temperature of outlet of low-pressure compressor is have not bad influence on the high-pressure compressor. So the temperature without severe cast down, it is not fine for health monitor.

Abstract: Aircraft engines are exposed to degradation due to several factors such as environmental air pollution, fuel content and ageing or degradation of engine’s components, which are experienced within specified time. While the turbofan in operation, its components deteriorate and consequently affect its performance. This study is aimed to computationally investigate the effect of components degradation on engine performance. A high bypass turbofan engine operated at cruise is selected for this evaluation and the simulation was performed using the Gas Turbine Simulation Program (GSP). The affected components considered are turbines and compressors with deterioration rate ranging from 0% to 5%. The effect of selected deterioration rate on engine thrust and thrust specific fuel consumption (TSFC) is studied. Results obtained show an agreement with literature where reduction in engine thrust and TSFC are observed. Turbine’s fouling has been found to be more severe than erosion in terms of power and efficiency losses. However, in terms of the overall performance, the erosion effect is more severe than fouling.