Impact of Relative Humidity of Supply Gas on Temperature Distributions in Single Cell of Polymer Electrolyte Fuel Cell When Operated at High Temperature

For improving the performance of stationary PEFC （polymer electrolyte fuel cell） system, the cell operating temperature up to 90℃ will be preferred in Japan during the period from 2020 to 2030. To understand the operation of the PEFC system under relatively high temperature conditions, detail heat and mass transfer analysis is required. The purpose of this study is to analyze the impact of relative humidity of supply gas on temperature distribution on the backside of separator in single ceil of PEFC using Nation membrane at higher temperature e.g. 90℃. The in-plane temperature distribution when power was being generated was measured using thermograph with various relative humidity of supply gases. It was found that the in-plane temperature distribution at the anode was more even than that at the cathode irrespective of the relative humidity of supply gas at the anode and the cathode. The temperature elevated along gas flow through the gas channel at the cathode irrespective of relative humidity of supply gas at the anode and the cathode. The in-plane temperature distribution at the cathode was narrower with the increase in Tini irrespective of relative humidity of supply gas at the cathode, while it was not observed when changing the relative humidity of supply gas at the anode. When the relative humidity of supply gas at cathode decreased, the in-plane temperature distribution at the anode was wider compared to decreasing the relative humidity of supply gas at the anode. The study concluded that the impact of relative humidity of supply gas at both anode and cathode had little impact on the in-plane temperature distribution at the cathode.

Effects of high temperature and high relative humidity drying on moisture distribution,starch microstructure and cooking characteristics of extruded whole buckwheat noodles

Drying is a key step in starch noodle production.The effects of high temperature(60,70,80°C)and high relative humidity(65%,75%,85%)drying(HTHD)on the moisture distribution,starch microstructure and cooking characteristics of extruded whole buckwheat noodles were investigated.Compared to the conventional hot-air drying(CHAD)at 40°C,the increase in drying temperature(60–80°C)and the decrease in relative humidity(85%–65%)significantly improved drying efficiency of the extruded noodles.By adjusting drying temperature and relative humidity,the rate of moisture migration in noodles and phase transition of starch could be appropriately controlled.The optimum drying parameters(T70H75,70°C drying temperature and 75%relative humidity)showed smooth and dense network structure,resulting in the lowest cooking loss(6.61%),broken rate(0%),highest hardness(1695.17 g)and springiness(0.92).However,the total flavonoid content(TFC)and the total phenolic content(TPC)reduced by 6.81%–28.50%and 7.19%–53.23%in contrast to CHAD,and the color of buckwheat noodles became darker through HTHD.These findings showed the potential of HTHD for increasing drying efficiency and improving buckwheat noodle quality.The appropriate drying parameters could maintain a balanced relationship between moisture migration in noodles and phase transition of starch,which resulted in better cooking quality for extruded whole buckwheat noodles.Such a study is valuable for regulating the process conditions of buckwheat-based foods and promoting its commercial utilization.

Effects of Extreme Air Temperature and Humidity on the Insecticidal Expression Level of Bt Cotton

The higher survival rates of Helicoverpa amigera larvae were usually observed after adverse climate which was related to extreme temperature （T） and relative humidity （RH） stresses in transgenic Bacillus thuringiensis （Bt） cotton. The unstable resistance of Bt cotton to bollworms has been correlated with the reduced expression of CrylAc δ-endotoxin. The objective of this study was to investigate the effects of combined temperature and relative humidity stresses on the leaf CrylAc insecticidal protein expression during critical developmental stages. The study was undertaken on two transgenic cotton cultivars that share same parental background, Sikang 1 （a conventional cultivar） and Sikang 3 （a hybrid cultivar）, during the 2007 and 2008 growing seasons at the Yangzhou University Farm, Yangzhou, China. The study was arranged with two factors that consisted of temperature （two levels） and relative humidity （three levels）. The six T/RH treatments were 37℃/95%, 37℃/70%, 37℃/50%, 18℃/95%, 18℃/70%, and 18℃/50%. In 2007, the six treatments were imposed to the plants at peak flowering stage for 24 h; in 2008, the six treatments were applied to the plants at peak square, peak flowering, and peak boll stages for 48 h. The results of the study indicated that the leaf insecticidal protein expression in CrylAc was significantly affected by extreme temperature only at peak flowering stage, and by both extreme temperature and relative humidity during boll filling stage. The greatest reductions were observed when the stresses were applied at peak boll stage. In 2008, after 48 h stress treatment, the leaf Bt endotoxin expression reduced by 25.9-36.7 and 23.6-40.5% at peak boll stage, but only by 14.9-26.5 and 12.8-24.0% at peak flowering stage for Sikang 1 and Sikang 3, respectively. The greatest reduction was found under the low temperature combined with low relative humidity condition for both years. It is believed that the temperature and relative humidity stresses may be attributed to the reduced efficacy of Bt cotton in growing conditions in China, where extreme temperatures often increase up to 35-40℃ and/or decrease down to 15-20℃, and relative humidity may reach to 85-95% and/or reduce to 40-55% during the cotton growing season.

Low-temperature combined with high-humidity thawing improves the water-holding capacity and biochemical properties of Portunus trituberculatus protein

This study compared the effects of conventional thawing methods(water immersion thawing(WIT,(25±1)℃),natural air thawing(AT,(25±1)℃,relative humidity(RH(65±2)per cent),refrigerator thawing(RT,4℃,RH(80±2)per cent)and low-temperature(LT)combined with high-humidity thawing LT,-1℃to 1℃(LT-1-1),2-4℃(LT2-4),5-7℃(LT5-7)and 8-10℃(LT8-10),RH>95 per cent)on the water-holding capacity,lipid oxidation and biochemical properties of Portunus trituberculatus(P.trituberculatus)myofibrillar protein.The results showed that WIT and AT significantly decreased the water-holding capacity while dramatically increasing lipid oxidation,protein oxidation and degeneration,resulting in serious P.trituberculatus quality deterioration.High humidity was beneficial for P.trituberculatus\.ha\A/\ng.The thawing time of P.trituberculatus under the conditions of LT2-4 was only 39.39 per cent of that of conventional air thawing at 4℃(RT),and the LT2-4 samples not only maintained better water-holding capacity but also had an obviously reduced degree of lipid oxidation,protein oxidation and denaturation.Thawed samples LT2-4 and LT5-7 provided better maintenance of P.trituberculatus quality than the LT-1-1 and LT8-10 samples.The best quality was exhibited after thawing at 2-4℃.The levels of thiobarbituric acid reacting substances,carbonyl content and surface hydrophobicity observably decreased in these samples,while the total sulfhydryl contents dramatically increased compared to those of conventionally thawed samples,indicating lower lipid oxidation and protein oxidation.Moreover,the Ca2+-ATPase activity of the sample thawed at 2-4℃(2.06 μmol Pi/mg prot/h)was markedly higher than that of samples subjected to WIT and AT.The product qualities observed after thawing at-1℃to 1℃,5-7℃and 8-10℃under LT were comparable to that observed by RT.Considering its thawing efficiency and product quality,LT is a suitable method for the thawing of P.trituberculatus,and the ideal thawing conditions were LT at 2-4℃.

Numerical Analysis of Temperature Distributions in Single Cell of PEFC by Heat Transfer Model Considering Vapor Transfer

Polymer Electrolyte Fuel Cell(PEFC)is required to be operated at temperature at 100℃ for fuel cell vehicle applications during the period from 2020 to 2025 in Japan.It is expected that micro porous layer(MPL)and thinner polymer electrolyte membrane(PEM)would enhance the power generation performance of PEFC at this temperature.The key objective of this study is to analyse the impact of MPL and thickness of PEM on the temperature distributions of interface between the PEM and catalyst layer at the cathode(i.e.,the reaction surface)in a single PEFC.A 1D multi-plate heat transfer model,considering vapor transfer,which is based on temperature data of separator measured using thermograph in power generation process.It is developed to evaluate temperature at the reaction surface.This study is investigated the effect of flow rate and relative humidity of supply gases on temperature distribution on reaction surface.The study reveals that the impact of flow rate of supply gas on temperature distribution on reaction surface is smaller with and without MPL.It is observed that the even temperature distribution on reaction surface as well as higher power generation performance can be obtained with MPL irrespective of thickness of PEM and relative humidity conditions.

低压静电场协同低温高湿解冻对牛肉嫩度和持水性的影响

为探究低压静电场协同低温高湿解冻对牛肉嫩度和持水性的影响,本研究以牛背最长肌为试验材料,分析了低压静电场解冻(电压2500 V,温度4℃,相对湿度50%)、低温高湿解冻(温度4℃,相对湿度98%)、低压静电场协同低温高湿解冻(电压2500 V,温度4℃,相对湿度98%)与低温解冻(温度4℃,相对湿度50%)四种解冻方式对冷冻牛肉剪切力、质构、水分分布、水分含量、持水性、感官评价的影响。结果表明:低压静电场协同低温高湿解冻的解冻时间最短(804 min),其中解冻损失(2.06%)、蒸煮损失(26.09%)与离心损失(15.00%)显著低于其余三种解冻方式(P<0.05),垂直肌纤维剪切力值(95.46 N)和平行肌纤维剪切力值(41.69 N)最低,自由水含量最低,水分迁移较少,水分含量(68.31%)最高,嫩度品质最优,该解冻方式样品的组织状态、气味、弹性及色泽均最优(总体可接受度最高);综上,低压静电场协同低温高湿解冻加快了牛肉解冻速率、减少了汁液流失,改善了牛肉持水性和嫩度,品质最佳。本研究结果将为低压静电场协同低温高湿解冻技术在冷冻牛肉解冻的产业应用提供理论依据。

高压静电场辅助解冻技术应用实验研究

随着食品保鲜需求的不断增长,冷库冷冻冷藏技术的优化及发展变得愈发重要。本研究评估了高压静电场辅助解冻在冷库中的应用效果,监测了冷库内部三层货架区域的各项参数,包括温度、湿度、风速变化以及货架电压分布。以冷冻猪肉作为实验样品,观察解冻速率、温度均匀性和解冻效果。研究结果表明,冷库三层货架的温度分布、相对湿度以及温度均匀度无显著性差异,但中层货架的电压最大,能够有效加快冷冻猪肉解冻速率,相比于电压微弱的下层,中层平均升温速率比下层提高78.7%左右,并保持良好的肉类解冻品质。本实验研究结果可为高压静电场技术在冷库食品解冻、贮藏保鲜等领域发展提供参考。

低温高湿变温解冻库的研制与应用

为解决现有冻肉解冻库解冻速率慢、营养流失大、解冻过程氧化劣变严重等问题，研制了一种新型的低温高湿变温解冻库，该解冻库由绝热库体、蒸汽加热加湿系统、变频制冷系统和控制系统组成。通过各系统的协调运作，使库内温度始终维持在2-8℃，相对湿度始终保持在90％以上，从而实现冻肉解冻过程中的有效保鲜。同时通过低温高湿变温解冻库解冻20t冷冻牛肉的加热负荷、制冷负荷、加湿蒸汽量及总蒸汽量等工艺参数的优化计算，研制出用于冷冻肉解冻的20t低温高湿变温解冻库，并进行了生产验证试验，比较分析了该解冻库与常规4℃解冻库对解冻牛肉品质的影响。结果表明，该低温高湿变温解冻库解冻入库平均温度为-18℃的20t冷冻牛肉耗时约12h，加热负荷为95．94kw，制冷负荷为18．77kW，加湿蒸汽量为8．78g／s，需要总蒸汽量为49．19g／s；与常规4℃解冻库相比，低温高湿变温解冻库解冻汁液流失率、汁液蛋白含量及解冻牛肉蒸煮损失率分别显著降低了44．17％，21．61％及20．30％，解冻牛肉肌红蛋白含量显著增加了41．04％，高铁肌红蛋白含量显著降低了58．69％，硬度及咀嚼性分别显著增加了39．86N及15．11N，实现了冷冻牛肉的保鲜解冻。该研究为低温高湿变温解冻库的研制提供了参考，有利于解决冷冻肉解冻过程中的品质劣变问题。

高湿度结合不同温度解冻对猪肉理化及蛋白特性的影响

探究相对湿度(relative humidity,RH)90%下,不同温度(0、4、8℃和12℃)解冻对猪肉品质特性的影响,以鲜肉和传统低温(4℃,RH 65%~73%)解冻肉为对照,分析处理组和对照组的解冻效率、保水性、嫩度、色泽、脂质过氧化、pH值、新鲜度的变化,并利用差示扫描量热仪和流变仪测定蛋白热变性及动态流变特性。结果表明:相较于传统低温解冻,高湿(RH 90%)、低温(0~12℃)解冻可提高解冻效率,且解冻后猪肉的保水性、色泽、嫩度显著提高(P<0.05),明显抑制脂肪氧化程度,降低蛋白变性程度,可最大限度维持“鲜肉”的品质;其中,高湿环境下4℃和8℃解冻效果明显优于0、12℃处理组,解冻后猪肉的保水性、色泽、嫩度得到改善,脂肪氧化程度降低,同时4℃和8℃解冻后猪肉蛋白变性程度较低,G′较高。因此RH 90%、4~8℃解冻是较合适的解冻条件,该条件可提高解冻效率、维持猪肉品质。

低温高湿解冻对南美白对虾保水性及肌原纤维蛋白生化特性的影响

以传统解冻——静水解冻、自然空气解冻及低温空气解冻为对照,通过考察解冻时间、保水性、pH值、色泽、质构、脂质氧化及肌原纤维蛋白生化特性变化,研究低温高湿条件(-1~1℃、2~4℃、5~7℃和8~10℃,相对湿度≥95%)对南美白对虾解冻效果及品质的影响。结果显示:静水解冻最快,仅需28.40 min,低温空气解冻最慢,耗时367.33 min。高湿有利于解冻,2~4℃时解冻速率较自然空气解冻、低温空气解冻提高了9.14%和57.62%。低温高湿(-1~7℃)解冻后,对虾保水性较高,2~4℃下解冻汁液流失最少,仅为传统解冻的16.32%~23.40%,离心失水率仅为2.80%;质构保持良好,2~4℃时质构最佳,硬度、咀嚼性显著高于传统解冻;脂质和蛋白质氧化明显改善,硫代巴比妥酸值显著低于传统解冻,总巯基含量明显提高,2~4℃解冻时表面疏水性甚至接近新鲜值,仅为7.69μg/mg(以每毫克蛋白质计);Ca^2+-ATPase活性较传统解冻显著上升,蛋白质变性程度较低。综合解冻效率、品质及生产实际,低温高湿解冻是一种较为理想的解冻方式。

高温高湿环境下不同填料沥青胶浆高温性能影响因素的优劣性研究

为探究高温高湿环境对不同填料沥青胶浆高温性能的影响,基于自行设计的室内饱水实验,采用动态剪切流变仪对矿粉、水泥、刹车片三种填料沥青胶浆进行动态剪切流变试验,通过XRD获得不同填料的化学元素,利用灰色关联法分析60℃下车辙因子与化学元素、温度和水分作用的关联性。试验结果分析表明,随着温度和水分作用时间的增加,沥青胶浆的复合剪切模量、车辙因子均呈增大趋势。经过不同饱水条件后,矿粉和水泥沥青胶浆的复合剪切模量、车辙因子相较于刹车片沥青胶浆变化更显著。不同试验条件下,化学元素对胶浆高温流变性能影响最大。在高温高湿环境下,建议采用Al2O3含量高的填料应用在路面上。

基于S7-1200的低温高湿度解冻库设计

为改进传统的肉类解冻方式的不足,提高解冻效率并且保证解冻完成后肉类的营养流失最少,根据先进的低温高湿度解冻理论,设计出低温高湿度解冻保鲜库,实现了肉类解冻以及食品保鲜功能。采用西门子S7-1200作为控制器,通过程序控制库内温湿度在设定范围并通过触摸屏以及计算机进行实时监测与控制。通过现场调试与运行,完善系统的可靠性,达到预期解冻效果,实现新型解冻保鲜模式的设计要求。

低温高湿解冻降低鲳鱼理化品质的劣变

本文以传统4℃空气解冻(RH 83±2%)为对照,研究低温高湿解冻(-1~1℃、2~4℃、5~7℃和8~10℃,RH≥95%)对鲳鱼解冻效果(解冻时间、解冻损失率)、肌肉品质(蒸煮损失率、持水性、p H、质构及脂质氧化)及其蛋白生化特性(表面疏水性、总巯基、蛋白、羰基含量及Ca2+-ATPase活性)的影响。结果表明,高湿有利于鲳鱼解冻,5~7℃时解冻效率较对照组提高42.47%。低温高湿(-1~7℃)条件下解冻、蒸煮和离心汁液流失均显著下降,肉质更新鲜;硬度、咀嚼性、胶黏性等均显著高于对照组,质构保持良好。肌原纤维蛋白生化指标结果显示,解冻会导致蛋白变性,但低温高湿解冻(-1~7℃)后蛋白变性程度显著降低,总巯基、蛋白含量、Ca2+-ATPase活性均显著高于对照组,而羰基含量则明显下降。与传统4℃空气解冻相比,低温高湿解冻能显著提高解冻效率,降低汁液流失,延缓鲳鱼在解冻过程中的品质劣变,提高解冻鲳鱼品质。