Performance of a modified direct expansion A/C unit

This technical note communicates the thermal performance of a modified ten‐Ton Refrigerant Direct Expansion (10‐TR DX) air conditioning unit into a chiller under actual operating conditions. The modified unit achieved higher COP and cooling capacity compared with conventional DX. The increase in the unit cooling capacity is basically attributed to the enhanced heat transfer coefficient of the Plate‐and‐Frame Heat Exchanger evaporator. Copyright © 2009 John Wiley & Sons, Ltd.     

Kinetic modeling and optimization of parameters for biomass pyrolysis: A comparison of different lignocellulosic biomass

A primitive element for the development of sustainable pyrolysis processes is the study of thermal degradation kinetics of lignocellulosic waste materials for optimal energy conversion. The study presented here was conducted to predict and compare the optimal kinetic parameters for pyrolysis of various lignocellulosic biomass such as wood sawdust, bagasse, rice husk, etc., under both isothermal and non-isothermal conditions. The pyrolysis was simulated over the temperature range of 500–2400 K for isothermal process and for heating rate range of 25–165 K/s under non-isothermal conditions to assess the maximum pyrolysis rate of virgin biomass in both cases. Results revealed that by increasing the temperature, the pyrolysis rate was enhanced. However, after a certain higher temperature, the pyrolysis rate was diminished which could be due to the destruction of the active sites of char. Conversely, a decrease in the optimum pyrolysis rate was noted with increasing reaction order of the virgin biomass. Although each lignocellulosic material attained its maximum pyrolysis rate at the optimum conditions of 1071 K and 31 K/s for isothermal and non-isothermal conditions, respectively, but under these conditions, only wood sawdust exhibited complete thermal utilization and achieved final concentrations of 0.000154 and 0.001238 under non-isothermal and isothermal conditions, respectively.     

Quantification of in situ temperature measurements on a PBI-based high temperature PEMFC unit cell

The temperature is a very important operating parameter for all types of fuel cells. In the present work distributed in situ temperature measurements are presented on a polybenzimidazole based high temperature PEM fuel cell (HT-PEM). A total of 16 T-type thermocouples were embedded on both the anode and cathode flow plates. The purpose of this study is to investigate the feasibility of the proposed temperature characterization method and to identify the temperature distribution on an operating HT-PEM in various modes of operation, including a 700 h sensors durability test. The embedded sensors showed minimal influence on cell performance, this difference seen in performance is believed to be caused by different bipolar plate materials. The measurement method is suitable for obtaining detailed data for validation of computational models, moreover the results indicate that the method can be used as a degradation tool, as it is possible to locate areas exposed to degradation, both in plane and between the anode and cathode.     

An energy demand model for a fleet of plug-in fuel cell vehicles and commercial building interfaced with a clean energy hub

This paper presents an energy demand model for a fleet of plug-in fuel cell vehicles and a medium-sized commercial/office building interfaced with a clean energy hub. The approach taken is to model the architecture and daily operation of every individual vehicle in the fleet. A simplified architecture model was developed, with daily operation divided into two periods: charging and travelling. During the charging period, the vehicle charges its batteries and refills its compressed hydrogen tanks. During the travelling period, the vehicle depletes the batteries and hydrogen tanks based on distance travelled. Daily travel distance is generated by a stochastic model. The modeling of the clean energy hub is also presented. The clean energy hub functions as an interface between electricity supply and the energy demand (i.e. hydrogen and electricity) of the vehicle fleet and the commercial building. Finally, a sample case is presented to demonstrate the use of the models.     

乳酸菌发酵制备大豆奶酪豆坯的工艺研究(英文)

采用3种乳酸茵干酪乳杆菌（LC）、瑞士乳杆菌（LH）和干酪乳杆菌鼠李糖亚种6013（LR）和葡萄糖酸内酯（GDL）凝固豆乳制备豆坯,并对其质构和风味进一步改善。在6h的凝乳发酵中可以发现LC＋LH样品中发酵剂生长良好,豆孔pH下降比LC＋LH＋LR样品要多。GDL的添加可以促进发酵剂生长,降低豆乳pH,但是它对豆坯的质构的改善并不明显。在GDL＋LH＋LC＋LR制备的豆坯样品中,检测到7种提供风味的和另外11种不同种类不同含量的游离氨基酸（FAA）,同时,该样品的脂肪酸（FA）情况也发生显著变化（C18：3．C20：0,C20：1和C22：0除外）。除了10种常规大豆脂肪酸外,C22：1和C24：0也被检测到。后熟过程中这些游离氨基酸和脂肪酸的变化将会导致大豆奶酪质构和风味的改善和提高。从质构和风味上讲,LC＋LH制备的豆坯是最好的,其次是LC＋LH＋GDL制备的豆坯。     

干酪乳杆菌鼠李糖亚种与肉葡萄球菌在大豆奶酪中的应用研究

研究了干酪乳杆菌鼠李糖亚种（Lactobacillus rhamnosus）与肉葡萄球菌（Staphylococcus cafnosus）在豆乳中的生长、产酸和凝乳的能力,结果表明,L．rhamnosus与S．cafnosus适合在豆乳中生长并具有很强的产酸和凝固豆乳的能力,2菌种之间没有相互抑制作用,当二者组合发酵3h时可使豆乳凝固;大豆发酵乳的SDS—PAGE、氨基氮分析及大豆乳清中蛋白质含量分析表明2菌种对蛋白质的降解没有显著性差异;质构分析表明菌种S．carnosus能明显降低大豆奶酪的硬度。     

Chemical composition,antioxidant and antimicrobial activities of basil (Ocimum basilicum) essential oils depends on seasonal variations

Chemical composition, antioxidant and antimicrobial activities of the essential oils from aerial parts of basil (Ocimum basilicum L.) as affected by four seasonal, namely summer, autumn, winter and spring growing variation were investigated. The hydro-distilled essential oils content ranged from 0.5% to 0.8%, the maximum amounts were observed in winter while minimum in summer. The essential oils consisted of linalool as the most abundant component (56.7–60.6%), followed by epi-α-cadinol (8.6–11.4%), α-bergamotene (7.4–9.2%) and γ-cadinene (3.2–5.4%). Samples collected in winter were found to be richer in oxygenated monoterpenes (68.9%), while those of summer were higher in sesquiterpene hydrocarbons (24.3%). The contents of most of the chemical constituents varied significantly (p < 0.05) with different seasons. The essential oils investigated, exhibited good antioxidant activity as measurements by DPPH free radical-scavenging ability, bleaching β-carotene in linoleic acid system and inhibition of linoleic acid oxidation. Evaluation of antimicrobial activity of the essential oils and linalool, the most abundant component, against bacterial strains: Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pasteurella multocida and pathogenic fungi Aspergillus niger, Mucor mucedo, Fusarium solani, Botryodiplodia theobromae, Rhizopus solani was assessed by disc diffusion method and measurement of determination of minimum inhibitory concentration. The results of antimicrobial assays indicated that all the tested microorganisms were affected. Both the antioxidant and antimicrobial activities of the oils varied significantly (p < 0.05), as seasons changed.     

Enhanced inactivation of pectin methyl esterase in orange juice using modified supercritical carbon dioxide treatment

The aim of the study is to quantify the effect of ethanol addition and exposure surface on the inactivation of pectin methyl esterase (PME), a juice clarifying enzyme, in orange juice using supercritical carbon dioxide (SC‐CO₂). Addition of ethanol to the SC‐CO₂ at 2% (v/v) caused greater inactivation than SC‐CO₂ alone, with a maximum reduction of PME activity of 97% at 30 MPa and 40 °C for 60 min. As the surface area to volume ratio was increased, the rate of inactivation of PME increased. Analysis of first‐order reaction kinetic data revealed that D values were greatly influenced by ethanol addition and agitation. With the addition of 2% ethanol, the D value reduced by half, that is, 56 min from 109 min. With impeller agitation of the sample at 1100 ± 100 rpm, the D value for PME was further reduced to 43 and 30 min without and with ethanol, respectively. The activity of PME treated with SC‐CO₂ remained unchanged after 14 days of storage at 4 °C. Treatment did not significantly change pH or colour, but did significantly increase the cloud values of the juice, resulting in a cloud stabilised juice with similar qualities to fresh juice.     

Viscous and thermal behaviour of vitamin A and iron‐fortified reconstituted rice

The viscous and thermal behaviour of five types of micronutrient‐fortified reconstituted rice premixes extruded at pre‐optimised extrusion conditions (36% moisture content, 150 rpm screw speed and 89 °C barrel temperature) have been investigated using rapid visco analyser (RVA) and differential scanning calorimetry (DSC). The highest peak viscosity (1279 cP), lowest gelatinised starch percentage (16.32) and highest enthalpy of gelatinisation (8.2 J g^?1) were recorded in rice premix fortified with retinyl palmitate and micronised ferric pyrophosphate. The scanning electron microscopic analysis (SEM) also revealed that reconstituted rice premix fortified with iron (micronised ferric pyrophosphate) and retinyl palmitate was in closer resemblance to that of natural rice than any other reconstituted rice premix. The work demonstrated that vitamin A‐ and iron‐fortified reconstituted rice with meso/micro structure and pasting behaviour close to that of natural rice can be produced using retinyl palmitate and micronised ferric pyrophosphate as vitamin A and iron source, respectively.