High Flux Values Research Articles

Investigating the performance of PBL parametrizations in WRF model for front enhanced SES simulation in istanbul megacity

Sea-effect snow (SES) is a meteorological phenomenon resulting from cold air moving over warmer waters. Accurate prediction of SES is vital for emergency management, transportation, and water resource planning. A thundersnow event in Istanbul from 17–19 February 2015 caused significant disruptions, with traffic and flights affected, highways temporarily closed, and trees falling due to heavy snowfall. This study investigates the influence of different parameterization schemes in the Weather Research and Forecasting (WRF) model on SES simulations. Six distinct PBL parameterization schemes were used in a series of WRF simulations. In addition, the following factors pivotal to SES event have also been investigated: 1000–500 hPa thickness, total and latent heat fluxes, radar and satellite analyses, temperature gradients, wind shear, inversion levels, and atmospheric stability indices. Additionally, the formation of SES during the cold front transition further contributed to these elements in the Black Sea region. The simulations displayed notably high total heat flux and latent heat flux values, particularly following the passage of the cold front. Furthermore, the northeast-southwest oriented SES cloud, distinguished by its banded structure, was successfully validated using radar and satellite imagery. However, it's worth noting that the model positioned it farther west than its actual location. This study highlights the challenges in precise prediction and analysis of such convective activities. In this thundersnow event, the local closure schemes, particularly MYNN in first place and second MYJ, demonstrated superior performance compared to non-local schemes within the parameterization options.

Preparation and In vitro/Ex vivo Evaluation of Nanoemulsion-Based in Situ Gel for Intranasal Delivery of Lasmiditan

Lasmiditan (LAS) was formulated as a nanoemulsion based in situ gel (NEIG)with the aim of improving its oral bioavailability via application intranasally. The solubility of LAS in oils, emulsifiers, and co-emulsifiers was determined to identify nanoemulsion (NE)components. Phase diagrams were constructed to identify the area of nanoemulsification. LAS NE was formulated using the spontaneous nanoemulsification method. Four NEs (F19, F24, F31, and F34) containing 7-15 % oleic acid (OA) as an oily phase, 40-55% labrasol (LR), and transcutol (TC) as emulsifier mixture at (1:1), (2:1), (3:1), and (1:2) ratio with 30-53 % (w/w) aqueous phase, having suitable optical transparency of 95–98%, globule size of 104-140 nm and polydispersity of 0.253–0.382 were selected for ex vivo permeation study. F31 with the highest flux value (2.32 ± 0.01 mg/cm2.min) relative to the other NEs. It achieves an enhancement ratio of 3.3 as compared to LAS aqueous suspension (8% LAS) also it achieves a significantly higher value of permeability coefficient. F31 was selected for the incorporation of different percentages of pH-sensitive in situ gelling polymer (Carbopol 934) to prepare NEIGs 4,5 and 6. The gel strength, pH, gelation time, and viscosity were predicted for the prepared NEIGs. In vitro release and ex vivo, nasal permeation were determined for NEIG5, which exerts comparable release and permeation values as F31 with more residence time in order to overcome the normal nasal physiological clearance.

Biocompatible polyethersulfone membrane modified by hydrophilic polymer decorated magnetic nanoparticles gilded by facile external magnetic field

AbstractPolymer‐based membranes such as polyethersulfone are widely used for hemodialysis and bio‐related applications; however, this type of membrane still fails to satisfy optimum performance in terms of clearance, safety, and bio‐adaptability. Herein, a polymer brush of polyvinylpyrrolidone is decorated on the surface of magnetic nanoparticles by using reversible addition‐fragmentation chain transfer polymerization (RAFT), and under the guidance of an external magnetic field, the prepared magnetic nanoparticles with the polymer brush system are blended with a polyethersulfone membrane during a liquid‐liquid phase inversion process. The prepared membranes with different loads of the pure magnetic nanoparticle and polyvinylpyrrolidone@magnetic nanoparticle polymer brushes are prepared, compared with the pristine membrane, the modified membrane shows a high flux value at 349 L m−2 h−1 and 99.9% bovine serum albumin protein rejection. This membrane also demonstrated improved hydrophilicity and pore structure compared with the pristine membrane. Concerning the blood biocompatibility analysis, the modified membranes acquire prolonged time for clotting factors such as prothrombin time, activated partial thromboplastin time, and thrombin time while exhibiting less fibrinogen concertation at 0.4 g L−1. Furthermore, for the first time, an innovative method for fouling detection based on magnetic field attenuation due to protein accumulation on the membrane surface is reported; the method in this work could be a positive booster for the safe use of polymeric membranes in hemodialysis and bio‐based applications.

Effectiveness of cellulose acetate composite membrane with the addition of zeolite additives to reduce TDS levels in peat water using a cross-flow reactor

The need for clean water continues to increase along with population and industrial growth, which causes a water crisis. Quantitatively, peat water has the potential to be managed as a source of clean water using membrane filtration. This study aims to compare the composition of the cellulose acetate-zeolite composite membrane in reducing TDS levels in peat water using a cross-flow reactor. Cellulose acetate-zeolite composite membranes were prepared by phase inversion technique using 15 wt.% cellulose acetate (CA), with variations in zeolite concentration (5%; 10%; 15%; 20% and 25%), contact time (20, 40 and 60 minutes), the reactor pressure was 1.5 bar, and the TDS concentration in the feed water was 1,201 mg/L. Membrane characterization was done through morphological analysis using a Scanning Electron Microscope (SEM) and tensile test analysis. Membrane performance is determined through permselectivity and permeability testing. The results showed that the highest flux value was obtained on a 5% cellulose acetate-zeolite membrane at the 20th minute, namely 78.8 L/m2.hour. The best composition was obtained on a 25% cellulose acetate-zeolite membrane with a tensile strength value of 54.089 MPa and a rejection value of 92%. Morphological characterization showed that the pore size of the cellulose acetate-zeolite composite membrane decreased after use because TDS particles covered it.

Critical heat flux at high mass velocities in a microchannel and surface tension measurements for R514a

This paper presents pioneer experimental data on critical heat flux (CHF) during flow boiling of low-pressure fluid R514a in a microchannel. The authors conducted experiments in a single smooth and horizontal microchannel, with an internal diameter of 1.1 mm and heating sections of 46 and 100 mm, a saturation temperature range of 56 to 122.7°C, and a mass velocity range of 1500 to 7500 kg/m2s. This research achieved high critical heat flux values, up to 1.85 MW/m2. The results were compared with the CHF of R123 under similar conditions and a higher CHF for R514a was observed. The performance of CHF predictive methods against the experimental data was performed. Since predictive methods for the CHF in microchannels need surface tension data, but there is a lack of experimental information about this property for R514a in the literature, this paper also presents experimental results for the surface tension of R514a and an expression for calculation of this property as a function of the temperature.

Condensation Flow of Refrigerants Inside Mini and Microchannels: A Review

Nowadays, the demand for obtaining high heat flux values in small volumes has increased with the development of technology. Condensing flow inside mini- and microchannels has been becoming a promising solution for refrigeration, HVAC, air-conditioning, heat pumps, heat pipes, and electronic cooling applications. In these applications, employing mini/microchannels in the condenser design results in the working fluid, generally refrigerant, undergoing a phase change inside the mini/microchannels. On the other hand, the reduction in the hydraulic diameter during condensation gives rise to different flow regimes and heat transfer mechanisms in the mini- and microchannels compared to the conventional channels. Therefore, the understanding of fluid flow and heat transfer characteristics during condensation of refrigerant inside mini- and microchannels has been gaining importance in terms of condenser design. This study presents a state-of-the-art review of condensation studies on refrigerants inside mini- and microchannels. The review includes experimental studies as well as correlation models, which are developed to predict condensation heat transfer coefficients and pressure drop. The refrigerant type, thermodynamical performance, and compatibility, as well as the environmental effects of refrigerant, play a decisive role in the design of refrigeration systems. Therefore, the environmental impacts of refrigerants and current regulations against them are also discussed in the present review.

Pressure fluctuations preceding critical heat flux during subcooled flow boiling in a one-side heated mini-channel under rolling motion

This study investigates effects of rolling motion on pressure fluctuations leading to Critical Heat Flux (CHF) during subcooled flow boiling in a mini-channel. Experiments were conducted at rolling amplitudes of 15° and 25° and periods of 10 and 30 s under two mass flow rates. Results obtained in static and rolling cases were compared. The rolling case showed higher pressure fluctuations, leading to higher CHF values, compared to the static case. The rolling intensity was the highest in the case with a higher amplitude and a shorter rolling period, whereas it was the lowest in the case with a lower amplitude and a longer rolling period. Correspondingly, the pressure fluctuations and CHF followed a similar trend, with the highest values observed in the case with the highest rolling intensity. The pressure fluctuations in the rolling experiments were also found to increase with increasing power, particularly at high heat flux values.

Gel Formulation and an In-vitro Kinetic Permeation Release Study of Cefixime Trihydrate and Chlorpheniramine Maleate (CCM)

Cefixime is an antibiotic drug used to treat infection. Chlorphenamine, also known as chlorpheniramine, is an antihistamine and used to treat allergic diseases such urticarial infections and rhinitis Objective: To formulate a gel by using propylene glycol (PG) along with Polyethylene glycol (PEG) in order to enhance the percutaneous absorption and release of cefixime trihydrate and chlorpheniramine maleate from TDDS (transdermal drug delivery system). Methods: Various formulations (G1 to G13) containing cefixime trihydrate and chlorpheniramine maleate gels (CCM gels) were prepared for this purpose with PG and PEG in different ratios. Firstly, gel optimization was estimated from the physical properties of the gels. Later, the diffusion process was carried out through Franz diffusion cells to find out the permeation kinetic parameters of these gel formulations. Only two of the gels (G1 and G3) were selected for further process while the rest were not employed due to stability issues. Results: The obtained results were analyzed by using statistical RSM (response surface methodology) and the link between the independent and response variables was depicted using contour plots. The result of the current study of both these gels indicated high values of flux and ER (enhancement ratio) while a reduction in tlag value. However, no significant difference was seen in the values I/R (input ratio) and Kp (permeation constant) with other formulated gels. Conclusions: It was concluded that the addition of PG and PEG into gels could enhance the permeation of cifixime trihydrate and chlorphenaramine mleate across membrane.

Methodology for modeling spray cooling of a cylindrical tube heated in the film boiling regime

This study examines spray cooling of horizontal, circular tubes when the surface temperature exceeds the Leidenfrost point, and the individual drop impacts are in the film boiling regime. Although film boiling is not an optimal condition for heat transfer, it is encountered in transient cooling processes or when high temperatures persist along the tube. The goal of the study is to apply existing models for drop impact and heat transfer to surfaces more complex than flat plates and to determine the overall steady state heat removal rate as an essential parameter for heat exchanger design. The spray characteristics are prescribed by a local number flux and drop size, assuming a random distribution in space and a uniform velocity of all drops. The angle of individual drop impingement on the cylindrical tube is accounted for through the maximum spreading diameter of the drop on the surface and the normal component of impact velocity. Furthermore, drop-drop interaction on the heated surface is accounted for at high local number flux values through an effective coverage area coefficient.The results are expressed in the form of a local heat transfer coefficient. These results confirm that the most influential parameters regarding heat transfer are the liquid mass flow rate in the nozzle and the drop diameter; however, they also indicate that the non-normal impact of drops over portions of the cylindrical tube leads to a highly reduced number flux; hence heat transfer. This oblique impact angle arises for one from the local spray angle, but more drastically from the curved, cylindrical surface; the latter leading to a dramatic sharp decrease in heat transfer. This is important information when considering the use of multiple spray nozzles, either circumferentially or longitudinally along the tube, since it dictates the optimal spacing between neighbouring nozzles.

Fabrication and Characterization of PSf/GO-SiO2 Membranes as Filtration of Detergent Contaminated Water

The increasing use of detergents in daily life can cause environmental pollution. So, to solve the problem, membrane technology is suitable to reduce various pollution from water. Graphene Oxide (GO) and SiO2 are very much of concern and have been studied in recent years because they can change many characteristics of materials and can expand the range of applications in membrane manufacturing. So, this study aims to analyze the results of PSf/GO-SiO2 membrane fabrication by phase inversion method and analyze the results of PSf/GO-SiO2 membrane performance as detergent polluted water filtration. In GO synthesis using Hummer’s method, GO-SiO2 composite synthesis using Tetraethylorthosilicate (TEOS) in-situ hydrolysis method, and PSf/GO-SiO2 membrane fabrication using the phase inversion method. So, it is concluded that the PSf/GO-SiO2 membrane fabrication has been successfully carried out, as indicated by the SEM results; with the increasing presence of SiO2, the membrane pore size is getting bigger. For the performance of the PSf/GO-SiO2 membrane with UV-Vis test, the results showed that the flux value of the PSf; PSf/GO and PSf/GO-SiO2 (0.6) membranes was 119.58 L/m2.h; 140.35 L/m2.h and 157.79 L/m2.h respectively. In line with the results of the membrane rejection values are 95.22%, 97.68%, and 98.55%, respectively. The membrane with the best performance in the filtration of detergent-polluted water is the PSf/GO-SiO2 (0.6) membrane. The presence of SiO2 in the membrane causes a higher flux value because the larger membrane pore size influences it, so the PSf/GO-SiO2 membrane can be used to filtrate detergent-contaminated water.

CdO-Nanografted Superhydrophobic Hybrid Polymer Composite-Coated Cotton Fabrics for Self-Cleaning and Oil/Water Separation Applications.

The current study presents a simple and cost-competitive method for the development of high-performance superhydrophobic and superoleophilic cotton fabrics coated with cadmium oxide/cerotic acid (CdO/CE)-polycaprolactone (PCL)- and cadmium oxide/stearic acid (CdO/ST)-polycaprolactone-grafted hybrid composites. X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy are used to characterize the CdO/CE-PCL and CdO/ST-PCL and polycaprolactone-modified cotton fabrics. Using an optical contact angle meter, the wetting behavior of corrosive liquids such as coffee, milk, tea, water dyed with methylene blue, strong acids (HCl), strong alkali (NaOH), and saturated salt solution (NaCl) on the CdO-CE/ST/PCL-modified cotton fabrics is assessed as well as the durability of CdO-CE/ST/PCL-modified cotton fabrics in corrosive liquids. Data obtained from the oil-water separation experiment indicate remarkable separation efficiency with oil purity values of ≥99.97 wt %, and high permeation flux values of up to 11,700 ± 300 L m-2 h-1 are observed for surfactant-stabilized water-in-oil emulsions via a gravity-driven technique. From the data obtained, it is concluded that the nano-CdO-grafted superhydrophobic hybrid polymer composite-coated cotton fabrics (CdO-ST/(CE)/PCL/CFs) can be utilized for self-cleaning and oil/water separation applications.

Design and analysis of cooling jacket developed for vacuum power tubes by multiphase cooling

The vacuum tubes are used extensively in electronic industries. The MW level of vacuum tube are used in RF amplifiers and microwave sources in different sectors like defence, nuclear energy, satellites and medical diagnostics. The first step in the indigenous development of MW level of vacuum tube is the design of its cooling jacket. The cooling jacket of vacuum tubes use hypervapotron (HV) fins which are known for providing efficient cooling in compact space. The key objectives of this paper are to finalize the jacket’s construction material, evaluate the cooling jacket’s heat transfer performance at the MW level of RF (radiofrequency) power, and forecast safe operating conditions for given conditions of high heat flux and water flow rates. In this design, the vacuum tubes’ external dimensions are taken into consideration when designing the cooling jacket. ETP copper (Electrolytic Tough Pitch copper) and copper-chromium-zirconium (CuCrZr) are likely materials for the jacket’s construction. For the aforementioned design of the cooling jacket, FEA (Finite Element Analysis) simulations using a steady-state thermal module and computational fluid dynamics (CFD) simulations using an ANSYS CFX module are described for flow rates of 15, 30, and 60 lpm (liters per minute) and the heat flux 1, 2, 4, and 6 MW m−2. The results of CFD and FEA simulations are found to be in close agreement. A small deviation in results is seen after the start of nucleate boiling. 30 and 60 lpm are desirable flow rates for high heat flux values greater than 2 MW m−2. CuCrZr is the ideal material for a cooling jacket’s construction as it has safe working temperature limit of 350 °C at high heat flux values. Also, 15 lpm flow rate should be avoided while using this cooling jacket at heat flux values greater than or equal to 6 MW m−2.

Analysis of the Causes of the Emergency Shutdown of Natural Gas-Fired Water Peak Boilers at the Large Municipal Combined Heat and Power Plant

The paper presents a cause-and-effect analysis of the failure of a 130 MWt gas-fired water boiler. The fault was a rupture of the helically finned tubes in the first rows of the second-stage water heater (ECO2). The high frequency of failures forced the boiler user to investigate their causes. The rapid drop in water flow in the ECO2 and the tightly finned pipes suggested that the permissible operating temperature of the steel used was exceeded. The only possible way to assess the working conditions was through a CFD simulation of the operation of the ECO2. Validated with the data acquisition system, the results show that the main reason for the failure was the overheating of the first rows of finned water heater pipes, regardless of the boiler load. The high heat flux value, exceeding 500,000 W/m2, and the increased flue gas temperature in front of the ECO2, almost reaching 900 °C, affected the appearance of the boiling film, limiting the cooling of the tube wall. Heat radiation and eddies behind the tubes significantly impacted the non-uniform temperature distribution, resulting in high pipe wall stress. By analyzing the service life of the first row of pipes based on the Larson–Miller parameter, it was concluded that the pipes would fail after only a few tens of hours.

Fabrication of high-performance MeI and HPEI assembled PES/CPES hollow fiber nanofiltration membranes with high positive charges for efficient removal of salt/heavy metal ions

Environmental protection and resource recovery require efficient separation of salts and heavy metal ions from wastewater. A new hollow fiber nanofiltration membrane (HFNM) with a highly positive charge was developed via Hyperbranched polyethyleneimine (HPEI) self-assembly and methyl iodide (MeI) quaternization on a polyethersulfone (PES) with carboxylic-PES (CPES) substrate. Effects of different layers on surface charge and roughness, wettability, and mechanical stability were evaluated. MgCl2 and ZnCl2 as representative of salts and heavy-metal ions, respectively, were used to investigate separating properties of the membranes in terms of feed temperature and concentrations, operating pressures, antifouling properties, and long-term stability. The relationship between salt/ions rejection and water flux, pore size, and surface positive charge degree was explained by comparing the structures and properties of the membranes. The 1wt.% HPEI and 0.5 wt.% GA solutions for 30 min crosslinking at pH of 11 and then 5 wt.% MeI solution could lead to the formation of the optimum membrane. Based on high hydrophilicity, low surface roughness, Donnan exclusion, and steric hindrance, the membrane could effectively exhibit superb rejection rates of Zn2+ (99.8 %), and Mg2+ (98.6 %), while showing high flux values (24.47 and 33.54 Lm−2h−1). The high flux rate (around 25.41 Lm−2h−1) during 4 cycles of regeneration, and high ions rejection (>98 %) were retained even after an 8-hour consistent operation. The prepared membrane, with high durability and structural stability, can introduce an effective solution for water purification from divalent ions.

Experimental investigation of pulsating heat pipes with different evaporator roughness values

Three transparent experimental setups of flat-plate pulsating heat pipes were investigated, each with a different channel surface roughness in the evaporator section. Roughness was varied using milling and sand blasting techniques. Experiments were conducted in different orientations with the refrigerant R1233zd(E) with filling ratios of 30%, 50% and 70%. Heat flux values between 5 and 45 W and condenser temperatures of 0 °C, 20 °C and 40 °C were applied. Low filling ratios, high condenser temperatures and high heat flux values were found to achieve the lowest thermal resistances. Increased surface roughness in the evaporator section also reduced the thermal resistance. The effect was especially pronounced for low heat flux values. The surface roughness in the evaporator section was analyzed with a confocal and a novel evaluation method with particular regard to the influence of the surface structure on the bubble nucleation behavior was introduced. The evaluation method yielded estimated bubble radius distribution profiles of the cavities found in the surface structure. The data was then used to calculate a mean bubble nucleation radius for the surface structure of each test setup. Combined with the pool boiling nucleation equation this resulted in a theoretical relative bubble nucleation threshold calculated for each measurement point. It was found that the theoretical bubble nucleation threshold could be directly correlated with the thermal resistance and overall performance of the pulsating heat pipe. In the experiments, bubble nucleation rates were determined by evaluating high-speed camera recordings using a bubble tracking algorithm. For a 70% filling ratio the bubble nucleation rate was found to increase up to a maximum with increasing heat flux. When approaching high heat flux values the bubble nucleation rate dropped again. The quantification of the connection between bubble nucleation threshold and thermal performance is a novelty in this work, as well as the quantification of the bubble nucleation rate in an experimental setup. The work offers meaningful insights into the thermo-hydraulic behavior of a PHP.

Optimisation of a micro-thermophotovoltaic with porous media inserted burner for electrical power improvement

To improve energy efficiency and electrical power output of H2-fueled micro-thermophotovoltaic, burning in combustors with varied porous media (PM) settings is experimentally and numerically studied. Effects of burner dimensions, PM settings and operating conditions on flow field, species distribution, combustion characteristics and heat transmission are investigated and analyzed. Results demonstrate that inserted PM strongly affects burning properties and combustor thermal performance, which is enhanced in larger size combustors. The combination of partially inserted PM with inlet-step is conducive to flame anchoring, improving the efficiency at higher flow rate in small combustor because of the high surface values of Nusselt number and heat flux. The fully inserted PM is beneficial to the heat transfer in chamber at lower flow rate and achieves the highest radiation power of large scale burner. The limit of flow rate is dramatically broadened with the augment of burner scale, such as mr = 2.65 × 10−5 kg/s to mr = 4.64 × 10−5kg/s, and the highest electrical power of micro-thermophotovoltaic system with burner 9D and InGaAsSb cells reaches to 2.81 W.

Bubble growth and departure behavior in subcooled flow boiling regime

Understanding the detailed dynamics of bubble ebullition cycle is central to effectively exploit coolant phase change in subcooled flow boiling. In the present study, the bubble growth rate and the bubble departure mechanism in subcooled flow boiling conditions are investigated. The bubble growth rate is estimated by employing an energy balance model, which ensures that the applied wall heat flux contribution to components, such as (i) microlayer evaporation, (ii) conduction through superheated layer region, and (iii) condensation heat transfer, are accounted. The bubble departure diameter and the type of departure (i.e., sliding or lift-off) are predicted using a simple force balance model on the vapor bubble. The implemented models are thoroughly validated against the benchmark experimental data. Furthermore, the influence of operating conditions, viz., pressure (1–3 bar), mass flux (200–1000 kgm−2s−1), heat flux (200–500 kWm−2), and the degree of subcooling (20–30 K) on the bubble dynamics, is investigated for subcooled flow boiling conditions. Based on the parameters considered, a flow regime map is developed to identify the bubble departure type and diameter for a given set of operating conditions. It was noticed that the bubble departure diameter was maximum at low pressure (1 bar), low mass flux (200 kgm−2s−1), high heat flux (500 kWm−2), and low degree of subcooling (20 °C). For all the values of pressure and degree of subcooling, the sliding mode of departure was noticed at low and high mass flux values, whereas bubble departs by lift-off for moderate values of mass flux.

Concentration levels, spatial variations and exchanges of polychlorinated biphenyls (PCBs) in ambient air, surface water and sediment in Bursa, Türkiye

In this study, ambient air, surface water and sediment samples were simultaneously collected and analyzed for PCBs to investigate their levels, spatial variations and exchanges between these three compartments at different sampling sites for 12 months in Bursa, Türkiye. During the sampling period, a total of 41 PCB concentrations were determined in the ambient air, surface water (dissolved and particle phase) and sediment. Thus, 945.9 ± 491.6 pg/m3 (average ± STD), 53.8 ± 54.7 ng/L, 92.8 ± 59.3 ng/L and 71.4 ± 38.7 ng/g, respectively. The highest concentrations of PCBs in the ambient air and in water particulate phase were measured at the industrial/agricultural sampling site (1308.6 ± 252.1 pg/m3 and 168.7 ± 21.2 ng/L, respectively), ∼ 4–10 times higher than background sites; while the highest concentrations in the sediment and dissolved phase were measured at the urban/agricultural sampling sites (163.8 ± 27.0 ng/L and 145.7 ± 15.3 ng/g, respectively), ∼ 5–20 times higher than background sites. PCB transitions between ambient air-surface water (fA/fW) and surface water-sediment (fW/fS) were investigated by fugacity ratio calculations. According to the fugacity ratios obtained, volatilization from the surface water to the ambient air was observed at all sampling sites (98.7 % of fA/fW ratios are <1.0). Additionally, it has been determined that there is a transport from the surface water to the sediment (100.0 % of fW/fS ratios are higher than 1.0). The flux values in ambient air-surface water and surface water-sediment environments ranged from −1.2 to 1770.6 pg/m2-day and from −225.9 to 0.001 pg/m2-day, respectively. The highest flux values were measured for PCBs with low chlorine content (Mono-, Di-Cl PCBs), while the lowest flux values were measured for the high chlorine content PCBs (Octa-, Nona- and Deca-Cl PCBs). As it was determined in this study that surface waters contaminated by PCBs have the potential to pollute both air and sediments, it will be important to take measures to protect surface waters.

Photosystem II Performance of Coffea canephora Seedlings after Sunscreen Application.

In the conilon coffee tree, the stress caused by high light can reduce the photosynthetic rate, limit the development and also reduce the yield of beans. Considering that the quality of a sunscreen spray can influence photosynthetic performance, the goal was to understand the iterations between the quality of the spray and the variation of the chlorophyll a fluorescence when applying sunscreen on conilon coffee trees. The parameters coverage, volumetric median diameter, density, droplet deposition, and the variation of the chlorophyll a fluorescence were evaluated. The nozzle and application rate factors did not show direct effects in the physiological responses of the plants. Plants with no sunscreen application showed high values of energy dissipation flux. The photosystem II (PSII) performance index and PSII photochemical maximum efficiency indicate that the use of sunscreen for plants promotes better performance of photosynthetic activity and that it provides photoprotection against luminous stress, regardless of the application rate and spraying nozzle; however, we recommend using the application rate of 100 L ha-1 and the cone jet nozzle type because they provide lower risks of product loss due to runoff.

CVD processed ZnO thin film as solid thermal interface material in electronic devices: thermal and optical performance of LED

Purpose Polymer-based thermal interface materials (TIMs) are having pump out problem and could be resolved for reliable application. Solid-based interface materials have been suggested and reported. The purpose of this paper is suggesting thin film-based TIM to sustain the light-emiting diode (LED) performance and electronic device miniaturization. Design/methodology/approach Consequently, ZnO thin film at various thicknesses was prepared by chemical vapour deposition (CVD) method and tested their thermal behaviour using thermal transient analysis as solid TIM for high-power LED. Findings Low value in total thermal resistance (Rth-tot) was observed for ZnO thin film boundary condition than bare Al boundary condition. The measured interface (ZnO thin film) resistance {(Rth-bhs) thermal resistance of the interface layer (thin film) placed between metal core printed circuit board (MCPCB) board and Al substrates} was nearly equal to Ag paste boundary condition and showed low values for ZnO film prepared at 30 min process time measured at 700 mA. The TJ value of LED mounted on ZnO thin film (prepared at 30 min.) coated Al substrates was measured to be 74.8°C. High value in junction temperature difference (ΔTJ) of about 4.7°C was noticed with 30 min processed ZnO thin film when compared with Al boundary condition. Low correlated colour temperature and high luminous flux values of tested LED were also observed with ZnO thin film boundary condition (processed at 30 min) compared with both Al substrate and Ag paste boundary condition. Originality/value Overall, 30 min CVD processed ZnO thin film would be an alternative for commercial TIM to achieve efficient thermal management. This will increase the life span of the LED as the proposed material decreases the TJ values.