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1.
文章基于某新型动车组空调通风系统结构,建立风道及客室计算域几何模型,进行风道及客室内送风过程的仿真计算,分析风道送风量及客室内流场分布情况,并根据仿真分析结果对当前的风道结构提出优化建议。  相似文献   

2.
不同组分纤维在纱线内混合不匀会导致混纺纱的强度降低、强力不匀恶化、布面色差等瑕疵增加.为探究条混工艺参数对混纺纱条混合均匀度的影响,通过改进混合不匀指数(IBI)表征混合均匀度,并采用计算模拟纤维在条混时的运动情况,获取混合纱条中纤维的分布规律.讨论了不同并合根数、并合道数、排列方式、混纺比等条混工艺参数对纱条混合均匀...  相似文献   

3.
目的:了解冷冻过程中改变排列方式与位置对马铃薯泥冻结特性与制冷设备能耗的影响。方法:使用Gambit完成了马铃薯泥鼓风冷冻的三维数值模型的建立,同时使用Fluent 6.3进行非稳态模拟;为验证模拟结果使用Pr.c-15型普龙通高效保鲜冷冻机进行马铃薯泥冷冻试验,试验中马铃薯泥采用顺排和叉排的排列方式,在此基础上改变马铃薯泥的位置(按顺时针旋转180°)以验证数值模型。结果:该数值模型与实际情况吻合,冻结时间相对误差仅为2.7%;相较于顺排的排列方式,叉排排列优势明显,冻结时间最多缩短了8.5%,能耗最多降低了4.5%,且温度变异系数和冻结时间不均匀度同样优势明显;马铃薯泥采用叉排排列方式时,分别在t=60 min 和t=120 min时刻改变位置,相较于位置不变,位置改变能够进一步缩短冻结时间,并且在保证冻品品质的前提下降低设备的能耗,与不进行任何优化措施相比(顺排排列且位置不变),采用叉排和二次改变位置的措施能使设备能耗降低11.8%。结论:在马铃薯泥鼓风冻结过程中改变其排列方式和位置会对马铃薯泥周围的流场分布产生影响,对冷冻过程的换热效果起到强化作用。  相似文献   

4.
介绍了基于悬浮式冷冻原理建造的中试装置,并分别采用鲜榨西瓜汁、速溶固体饮料和工业盐水三种溶液进行试验,研究各物料的初始浓度、冷冻温度和出料温度三个关键指标参数对冷冻浓缩效果的影响。通过试验得到当浓度控制在6.2g/100g,载冷剂冷冻温度控制在-4℃,并且出料温度控制在-4℃时,冷冻浓缩的效果最好。  相似文献   

5.
孙欢  杨凯  刘晓彤 《食品与机械》2024,41(2):78-83,138
目的:在直冷式块冰机冰模蒸发器内部增设冷冻剑以实现快速制冰。方法:使用COMSOL模拟冷冻剑截面形状及冷冻剑倾角对制冰过程的影响。结果:随着制冰过程的持续进行,增设不同截面形状冷冻剑的冰模内部平均温度不断降低,冰模内固相体积分数也随时间而增加,但在相同时间内增设圆形截面冷冻剑的冰模内部平均温度要比三角形、矩形和菱形低0.1~0.2 ℃。此外,冷冻剑倾角越小制冰速率越快。结论:冷冻剑截面形状为圆形或近圆形时,制冰速率较快;且在保证便于脱冰的前提下,应尽可能减小冷冻剑倾角。  相似文献   

6.
本文研究了不同发酵时间、不同冷藏时间条件下冷冻面团的裂纹情况、冻缩情况、成品高径比、比容、质构及口感等品质指标的变化。结果表明:随着发酵时间的增加,面团裂纹情况、皱缩情况呈增加趋势,高径比呈减小趋势,综合各个品质指标,确定了最佳发酵时间为10min;随着冷藏时间的增加,在短期内面团品质及成品品质所受的影响较小,但是随冷藏时间的继续增加,成品的色度和比容会明显下降,最后综合各品质指标确定冷藏时间不宜超过8天。  相似文献   

7.
本文研究了不同发酵时间、不同冷藏时间条件下冷冻面团的裂纹情况、冻缩情况、成品高径比、比容、质构及口感等品质指标的变化。结果表明:随着发酵时间的增加,面团裂纹情况、皱缩情况呈增加趋势,高径比呈减小趋势,综合各个品质指标,确定了最佳发酵时间为10min;随着冷藏时间的增加,在短期内面团品质及成品品质所受的影响较小,但是随冷藏时间的继续增加,成品的色度和比容会明显下降,最后综合各品质指标确定冷藏时间不宜超过8天。  相似文献   

8.
潘珂 《粮油加工》2008,(8):81-82
小麦面筋以其可以形成具有一定的机械强度的网状弹性结构的物理特性,使得小麦能有效和广泛地应用于食品。冷冻工艺可以使小麦面筋蛋白发生物理变性:在不同的冷藏时间下,面筋起泡性有不同的变化;本文主要讨论冷冻工艺对小麦面筋起泡性的影响。通过测定不同保藏时间下的小麦面筋的起泡性值,确定面筋起泡性的变化规律。结果表明,面筋起泡性随着冷冻时间的增长呈递减变化。  相似文献   

9.
10.
面筋对冷冻面团品质的影响   总被引:1,自引:0,他引:1  
就面筋对冷冻面团品质的影响进行研究,主要考察不同的面筋添加量、不同的时间指标以及成品馒头品质的变化等方面对冷冻面团品质的影响规律.结果表明:面团较好的醒发时间为15 min,冷冻时间为4d,面筋添加量为0.9%时,面团的粉质特性较好,成品馒头的评分最高.这为利用面筋来改良冷冻面团的品质,为实际生产实践选取合适的食品添加剂的应用奠定了理论基础.  相似文献   

11.
以冰箱冻结牛肉为研究对象,考虑牛肉冻结过程中变物性特点,采用等效热容法处理相变潜热,再用计算流体力学(CFD)数值模拟技术对该冻结过程进行模拟,并建立描述三维食品冻结过程的微分方程,通过数值模拟得出冻结时间的模拟值,各测点(T1、T2、T3、T4、T5)模拟计算的冻结时间与试验冻结时间的误差分别为5.45%,3.90%,5.80%,4.24%,9.60%,各点实时温度的模拟平均误差是1.79℃。结果表明,数值模拟能较好地预测牛肉的冻结时间。  相似文献   

12.
虾仁热物性的计算及冻结时间的数值模拟   总被引:2,自引:0,他引:2  
在虾仁热物性参数计算和等效比热容处理潜热的基础上,采用有限差元法对不规则虾仁建模,分别预测虾仁对称截面距冰箱冷冻层底部15,50,100mm处的冻结时间,在该基础上,对冰箱冻结虾仁进行实验验证。通过数值模拟与实验验证结果的对比发现,模拟冻结时间与实验冻结时间曲线相关系数为0.996,虾仁切面中心测点的最大误差值为1.85K,说明该数值模拟方法可以有效预测食品冻结过程中温度分布,对虾仁的冷冻加工、品质控制以及设备的优化具有重要意义。  相似文献   

13.
The effects of freezing temperature (−80, −40 or −24 °C) and thawing mode (microwave or overnight at 4 °C) on quality parameters of mashed potatoes made from tubers (cv Kennebec) and from potato flakes were examined, as was the effect of long‐term frozen storage on the quality of mashed potatoes. Mashed potatoes were tested for texture profile analysis (TPA) and cone penetration, oscillatory and steady rheometry, colour, dry matter, Brix and sensory analyses. In natural mashed potatoes, TPA hardness and oscillatory parameters showed that processing resulted in a softer product than the fresh control. The parameters were lower in the samples thawed at 4 °C than in those thawed by microwave at all the freezing temperatures used, which may be ascribed to gelatinisation of the starch released from damaged cells. Differences from the freshly prepared product decreased when the samples were frozen at −80 °C and thawed by microwave. No difference was found in sensory acceptability between samples frozen at −80 and −40 °C, which probably reflects the panellists' mixed preferences for air‐thawed versus microwave‐thawed samples. Increasing the time in frozen storage led to a natural mash with a firmer texture, higher L*/b* value and Brix; nonetheless, panellists found the samples at 0, 3 and 12 months of frozen storage equally acceptable. In commercial mash, penetration and oscillatory parameters showed that processing made for a firmer product than the fresh control, probably owing to retrogradation of gelatinised starch. Thawing mode had a significant effect on parameters, which were lower in the samples thawed at 4 °C. The structure and quality of commercial mash was more detrimentally affected by freezing and, therefore, we would not recommend either freezing or frozen storage of this mashed potato in the used conditions. Natural mash made from Kennebec potatoes should be frozen quickly and thawed by microwave in the conditions described to obtain a product more similar to that freshly made. If the samples are frozen by air blasting at −40 °C, the product can withstand frozen storage for one year. Copyright © 2005 Society of Chemical Industry  相似文献   

14.
15.
王金锋  李文俊  谢晶 《食品与机械》2016,32(10):200-204
文章主要通过综述冻结过程的数值模型、求解微分方程、预测冻结时间及分析送风速度、温度和送风方式等,讨论数值模拟技术在食品冻结过程中的应用现状;总结了国内外研究者针对不同冻结对象所采用的数值模拟方法,为今后数值模拟方法在食品传热过程中进一步发挥作用提供理论参考。  相似文献   

16.
Effects of modified cornstarch concentration, freezing rate and thawing mode on quality properties of mashed potatoes were examined. The product was tested by oscillatory rheometry, instrumental texture profile analysis (ITPA) and cone penetration, colour, dry matter (DM) and sensory analyses. Oscillatory parameters showed that increasing starch concentration resulted in a softer product in which gel strength decreased in direct proportion to concentration in quick‐frozen and microwave‐thawed product. Quick freezing made for firmer mashed potatoes, whereas oscillatory, ITPA and penetration parameters were lower in the samples thawed at 4 °C. Starch concentration and instrumental consistency and firmness were directly proportional to one another. Adding starch at the highest concentration, quick freezing and slow thawing produced a lighter‐coloured mashed potato, although the loss of colour in the processed product was not detected by panellists in the microwave‐thawed samples. DM was higher in the quick‐frozen samples and lower in air‐thawed samples. The factors studied affected different sensory texture parameters but had hardly any effect on attributes perceived during final and residual phases of mastication. Only starch concentration had a significant effect on sensory acceptability, but interactions between factors showed that starch addition followed by quick freezing was judged undesirable by the panellists due to excessive softening. Oscillatory parameters correlated well with sensory texture attributes and proved quite precise. They would therefore appear to be the best test to monitor properties of frozen mashed potatoes. Copyright © 2007 Society of Chemical Industry  相似文献   

17.
费达  王万荣 《中华纸业》2006,27(1):67-68
新型碱炉一般采用三层供风系统。合理的三次供风的风量分配,合适的二次风分布,适宜的温度、压力和烟气残氧量,可以减少碱炉飞灰形成,延长碱炉的运行周期,以达到碱炉安全、连续、高效地运行。  相似文献   

18.
为分析供气压力对辅助喷嘴气流中心线的影响,以避免出现虚假汇交现象,首先对主辅喷射气流产生虚假汇交现象进行理论分析,在此基础上利用气体流场测试装置,以泰坦TT-800喷气织机为实验平台,在改变供气压力条件下,对津田驹HTS1-9D的D型辅助喷嘴的实际流束中心线进行了测试分析。结果表明,当辅助喷嘴供气压力增大时,到达筘槽内侧的辅助喷嘴实际气流中心线与辅助喷嘴几何中心线之间的垂直距离逐渐增加。在实际织造生产中,可根据到达筘槽内侧的辅助喷嘴实际气流中心线与辅助喷嘴几何中心线之间的垂直距离的变化,来适当调节辅助喷嘴的安装高度,以避免出现虚假汇交现象,提高织造效率。  相似文献   

19.
脱蜡处理为枸杞干燥前处理工艺中重要环节之一,影响枸杞干燥速率和干燥品质。为获得更短的干燥周期和更好的干燥品质,以温度、时间、溶液比为实验因素,进行枸杞脱蜡单因素实验和Box-Behnken Design响应面优化法研究。结果表明,枸杞最优脱蜡参数组合为脱蜡时间12 min,脱蜡温度38℃,脱蜡溶液比1∶2,在此条件下干燥时间为21.5 h。验证实验和品质鉴定结果显示,最优脱蜡工艺缩短了枸杞的干制时间,保留了枸杞营养成分。   相似文献   

20.
Changes in individual sugar content (fructose, glucose and sucrose) during freezing and frozen storage have been evaluated by HPLC on papaya (Carica papaya grupo Solo var Sunrise), fruits proceedings from female and hermaphrodite flowers, and banana (Musa cavendishii var enana). Effects of thermal treatments, such as blanching and microwaving, prior to freezing banana fruit were examined. Both an increase in total sugar levels of papaya samples during freezing and a decrease in sucrose, by invertase, were found followed by an increase in fructose and glucose. A slight decrease in total sugars of banana samples during freezing and storage has been observed, with no significant differences between the pretreatments applied. © 1998 SCI.  相似文献   

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