Water droplet accumulation and motion in PEM (Proton Exchange Membrane) fuel cell mini-channels

Effective water management is one of the key strategies for improving low temperature Proton Exchange Membrane (PEM) fuel cell performance and durability. Phenomena such as membrane dehydration, catalyst layer flooding, mass transport and fluid flow regimes can be affected by the interaction, distribution and movement of water in flow plate channels. In this paper a literature review is completed in relation to PEM fuel cell water flooding. It is clear that droplet formation, movement and interaction with the Gas Diffusion Layer (GDL) have been studied extensively. However slug formation and droplet accumulation in the flow channels has not been analysed in detail. In this study, a Computational Fluid Dynamic (CFD) model and Volume of Fluid (VOF) method is used to simulate water droplet movement and slug formation in PEM fuel cell mini-channels. In addition, water slug visualisation is recorded in ex situ PEM fuel cell mini-channels. Observation and simulation results are discussed with relation to slug formation and the implications to PEM fuel cell performance

High temperature (HT) polymer electrolyte membrande fuel cells (PEMFC) - A review

One possible solution of combating issues posed by climate change is the use of the High Temperature (HT) Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) in some applications. The typical HT-PEMFC operating temperatures are in the range of 100e200 o C which allows for co-generation of heat and power, high tolerance to fuel impurities and simpler system design. This paper reviews the current literature concerning the HT-PEMFC, ranging from cell materials to stack and stack testing. Only acid doped PBI membranes meet the US DOE (Department of Energy) targets for high temperature membranes operating under no humidification on both anode and cathode sides (barring the durability). This eliminates the stringent requirement for humidity however, they have many potential drawbacks including increased degradation, leaching of acid and incompatibility with current state-of-the-art fuel cell materials. In this type of fuel cell, the choice of membrane material determines the other fuel cell component material composition, for example when using an acid doped system, the flow field plate material must be carefully selected to take into account the advanced degradation. Novel research is required in all aspects of the fuel cell components in order to ensure that they meet stringent durability requirements for mobile applications.Web of Scienc

Effect of extraction conditions on the soluble oxalate content in water infusions of green and herbal teas

Celem pracy było porównanie zawartości rozpuszczalnych szczawianów (RSZ) w wodnych naparach herbat zielonych i herbatek ziołowych uzyskiwanych przy zastosowaniu czterech sposobów ekstrakcji, tj. tradycyjnej metody ekstrakcji przy użyciu wrzącej wody o temp. 100 ºC, ekstrakcji wspomaganej promieniowaniem mikrofalowym w temp. 80 ºC (EWPM), ekstrakcji wspomaganej ultradźwiękami w temp. 40 ºC (EWU-40) i w temp. 60 ºC. Oznaczona metodą manganianometryczną średnia zawartość RSZ w badanych naparach była największa po zastosowaniu metody EWPM i wynosiła od 7,73 do 14,89 mg/g s.m. w herbatach zielonych oraz od 3,53 do 18,11 mg/g s.m. w herbatkach ziołowych. Natomiast najmniejsze wartości otrzymano po zastosowaniu metody EWU-40, tzn. od 5,06 do 10,88 mg/g s.m. w herbatach zielonych oraz od 1,5 do 11,03 mg/g s.m. w herbatkach ziołowych. W przypadku herbatek ziołowych, pobranych do badań wyłącznie w saszetkach do parzenia ekspresowego, stwierdzono istotną zależność pomiędzy ilością oznaczonych RSZ a rodzajem części anatomicznych wyjściowego surowca roślinnego. Podobnie, jak w przypadku herbat zielonych, największą średnią zawartością RSZ charakteryzowały się napary uzyskane metodą EWPM z herbatek ziołowych z całych liści, np. mięty – 18,11 mg/g s.m., szałwi – 12,23 mg/g s.m. oraz pokrzywy – 11,76 mg/g s.m. Z owoców (nasion) kopru włoskiego uzyskano RSZ na poziomie 3,53 mg/g s.m. produktu, a z kwiatostanu lipy 4,01 mg/g s.m. Wyjątek w tej grupie naparów stanowił kwiatostan rumianku, w którym oznaczono 16,05 mg/g s.m. produktu. Uzyskane wyniki mogą zostać wykorzystane do standaryzacji metod analitycznych stosowanych podczas oznaczania RSZ w naparach herbat zielonych i herbatek ziołowych w celu identyfikacji kraju i regionu ich pochodzenia, rozpoznawania okresu zbiorów i sposobu produkcji, ujawniania domieszek i zafałszowań oraz weryfikacji przydatności do spożycia i potwierdzania jakości zdrowotnej takich produktów.The objective of this research was to compare the content of soluble oxalates (SO) in water infusions of green and herbal teas made using four different extraction procedures, i.e. a traditional extraction procedure with boiling water of 100°C, a microwave radiation supported extraction at 80 °C (EWPM), and an ultrasound supported extraction at 40°C (EWU-40) and at 60 °C. The average SO content in the water infusions analyzed, determined by a manganometric method, was the highest after the microwave EWPM procedure of extraction was applied; it ranged from 7.73 to 14.89 mg/g (dry mass) as for the green teas and from 3.53 to 18.11 mg/g as for the herbal teas. The lowest values were obtained after the use of ultrasound EWU-40 procedure; those values ranged from 5.06 to 10.88 mg/g as for green teas, and from 1.5 to 11.03 mg/g as for herbal teas. In the case of herbal teas delivered for the analysis in tea bags for instant brewing, a significant dependency was found between the SO amounts determined and the kind of anatomical parts of the initial raw material. Similarly to the green teas, the water infusions prepared from whole herbal tea leaves with the use of EWPM procedure were characterized by the highest SO content, for example: peppermint tea: 18.11 mg/g; sage tea: 12.23 mg/g; and nettle tea: 11.76 mg/g. In the case of fennel fruit (seed) tea, the content of soluble oxalate determined was at a level of 3.53 mg/g of dry matter of the product, and in the case of linden inflorescence tea: at a level of 4.01 mg/g of dry matter. The exception in this group was the camomile inflorescence tea with a 16.05 mg/g of SO content determined. The results obtained can be applied to standardize analytical procedures used to determine SO contents in imported green teas and local herbal teas for such purposes as: identification of the country and region of origin of a given tea; fixing the harvesting period and determining the type of production process; finding admixtures and stating/excluding falsification; verifying the declared expiration date; and confirming the healthful properties (quality) of those products

Chlamydophila pneumoniae antibodies may be independently associated with increased BMI and percentage of body fat among women

Objective: To examine the potential association between Chlamydophila pneumoniae infection and obesity indicators after controlling for nutrient and energy intake, as well as age, smoking status, physical activity and educational level. Subjects: A total of 118 healthy adult females randomly recruited from the local community of Bydgoszcz, aged 20–80 years. Methods: Serum was tested for specific IgG antibodies against C. pneumoniae using qualitative enzyme linked immunosorbent assay. Usual dietary intake was assessed by a 7-day food record. Information regarding smoking, physical activity and educational level was collected using the questionnaire. Body mass index (BMI) and percentage of total body fat (%FM) were calculated respectively, as weight (kilograms) divided by height (meters) squared and with the equations of Durnin and Womersley. Results: The prevalence of C. pneumoniae infection was significantly higher among overweight/obese subjects (77.1 vs 60.0%; P=0.047) in comparison with normal-weight individuals. Using multivariate regression analysis, a significant positive association of BMI (β=0.194; P=0.036) and %FM (β=0.176; P=0.049) with C. pneumoniae IgG antibody positivity was found after adjustment for age, total energy intake, percentage of energy from fat, carbohydrate and protein, physical activity, educational level and smoking habits. Moreover, the multivariable adjusted odds ratio of being overweight/obese for the seropositive group compared with seronegative individuals was 1.70 (95% confidence interval: 1.02–2.89; P=0.037). Conclusion: The results indicated that C. pneumoniae infection may be associated with a risk of becoming overweight/developing obesity independently of dietary and lifestyle factors