基于多元回归分析的纬平织物热湿舒适性能

根据纬平织物的热湿传递机制和热湿舒适性能指标,提出利用回归分析的方法研究工艺参数对其热湿舒适性能影响程度的方法.利用测得的纬平织物热湿舒适性能指标运用多元回归分析的方法建立热湿传递规律的数学模型,并利用统一目标法建立纬平针织物热湿舒适性能的综合评价体系.结果表明:纬平织物的热舒适性能主要取决于织物的导热系数和织物厚度;...     

喷水织机加捻丝织物的设计与生产(2)

(续上期 )3 3 3　捻系数设计捻度是织物产生绉效应的重要手段 ,捻度越大 ,织物的绉效应越明显 ,但并不是捻度越大越好 ,捻度过大会给生产带来不便 ,如需增加捻丝设备 ,增加定形难度等 ,用强捻丝作纬丝时应特别注意可织性问题。捻系数可用下式计算 :捻系数 =Ｔ× Ｄ式中　Ｔ———每米捻数 ,捻 /ｍ ;　Ｄ———丝线纤度 ,Ｄ。在测纬装置是电测纬器的喷水织机上制织纬向捻线型织物时 ,纬丝捻系数的大小对可织性有很大影响 ,因喷水织机靠水力单向投纬 ,纬丝先端处于自由状态 ,每次投纬纬丝是否能到达织物另一端靠测纬器监测 ,从理论上讲 ,当…     

针织物热湿舒适性能的计算机仿真研究

在对针织物热湿舒适性能的理论分析和对实测数据研究的基础上，进行了各结构参数影响相关的热湿性能指标的计算机辅助研究，建立了数学模型。从而对各结构参数对针织物热湿性能影响的程度进行了定量分析。     

针织物热湿舒适性能的测试与研究

在对针织物热湿舒适性能的理论分析和对实测数据研究的基础上，进行了各结构参数影响相关的热湿性能指标的计算机辅助研究，建立了数学模型。从而就各结构参数对针织物热湿性能的影响程度进行了定理的深入分析。     

涤纶长丝衬里织物收缩性研究

织物在生产加工中多次受到热、湿作用而产生收缩,使得织物的尺寸结构不断发生变化.为确切反应织物的收缩情况及织物残余缩率,针对涤纶长丝织物进行沸水处理、干热定型处理和高温热湿处理,测其缩率的变化.结果表明在每一步处理中热、湿及张力因素都会对织物的收缩产生不同程度的影响,在松弛热定型和紧张热定型时织物的总缩率不同,且织物最终的机械性质也会发生相应的变化.     

量化衣物舒适度

影响人体感觉衣物是否舒适的3个主要系数是：热湿舒适度、手感舒适度及压力舒适度。其中热湿舒适度占整体感觉的50％，所以衣物的液态水分管理能力明显影响着人们对衣物湿度及舒适度的感觉。     

针织物热湿舒适性能的计算机仿真研究

本文在对针织物热湿舒适性能的理论分析的对实测数据研究的基础上，进行了各结构对数影响相关的热湿性能指标的计算机辅助研究，建立了数学模型。从而对各结构参数对针织物热湿性能的影响程度进行了定量的深入分析。     

基于灰色关联模型的针织物热湿舒适性分析与预测

为了实现对针织物热湿舒适性能的预测,对7种针织物进行物理性能测试,对影响针织物热湿舒适性的因素进行了灰色关联度分析,得出对热湿舒适性影响显著的针织物性能指标主要为瞬间冷暖感、导热系数、透湿量、厚度;在此基础上,运用灰色预测方法建立了针织物热湿舒适性与针织物测试性能指标之间的灰色关联模型,从而在得知针织物的瞬间冷暖感、导热系数、透湿量、厚度的情况下实现对针织物热湿舒适性的预测分析。     

医用防护服的热湿舒适性与人体疲劳度的关系

针对医护人员长时间穿着医用防护服工作导致体感闷热潮湿、疲劳增加、工作效率降低的问题,设计真人穿着试验,分析人体的热生理和主观感觉参数,从医用防护服的热湿性能角度分析对人体疲劳度的影响。试验结果表明:搭配短袖套装的防护服热湿舒适性最好,搭配长袖厚款套装的防护服热湿舒适性最差;穿着不同热湿性能的防护服在进行不同强度的运动中对人体疲劳度的影响不同,穿着防护服在静坐状态下,人体疲劳程度差异较小;在低、中、高强度运动和恢复状态下,防护服热湿舒适性越差,人体疲劳程度越深;平均皮肤温度、心率、能量代谢当量参数与主观疲劳感呈显著相关性,通过回归分析得到疲劳感与心率的模型,心率可以反映人体的疲劳程度。     

针织物热湿舒适性能的计算机仿真研究

在对针织物热湿舒适性能的理论分析和对实测数据研究的基础上 ,进行了各结构参数影响相关的热湿性能指标的计算机辅助研究 ,建立了数学模型。从而对各结构参数对针织物热湿性能影响的程度进行了定量分析     

ELECTRIC FIELD EFFECTS ON THE THERMAL CONDUCTIVITY OF MILK CHOCOLATE DETERMINED USING THE "MIRROR IMAGE METHOD"

Electrorheological fluids exhibit changes in flow properties when exposed to an electric field. Generally, these fluids display an increase in apparent viscosity and a greater yield stress in the presence of a voltage. Another attribute of some electrorheological fluids is the ability to enhance heat transfer, allowing for greater control over heating and cooling unit operations. This paper examined the effects of an applied voltage on the thermal conductivity of molten milk chocolate, a material known to be an electrorheological fluid. The method used to measure the thermal property was based on the “mirror image’ concept. In this technique, identical disks sandwich a heat source providing a constant heat flux directed evenly between the two sides. Knowing the heat flux and the boundary temperatures of the sample gap, an analytical solution was used to calculate the thermal conductivity and specific heat. An applied electric field of up to 450 V mm^?1 at 60 Hz was found to have no significant effect on the heat transfer properties of milk chocolate. The thermal conductivity was found to have an average value of 0.163 W m^?1 K^?1 over a temperature range varying from 25 to 60C. The measurement technique, however, proved to be a rapid method for determining thermal properties that may be useful in investigating other liquid foods.     

Combined Effect of Sucrose and Heat Treatment Temperature on the Thermal Resistance of Staphylococcus aureus MF-31

The combined effect of sucrose and heat treatment temperature on the thermal resistance of Staphylococcus aureus MF-31 was examined by determining the relationships between the D value, temperature and each of three parameters (water activity, osmotic pressure and water binding energy) related to sucrose-water binding. The results showed that sucrose and temperature had a significant interactive effect on thermal resistance. More specifically, sucrose increased the heat resistance, and this effect was greater at lower temperatures than at higher temperatures. The effect of sucrose on the Z value was slight compared to its effect on the D value.     

平房仓储粮生态多场耦合系统水分迁移传递机理研究综述

为确保国家粮食安全,满足工程重大需求,控制粮食储藏环境,抑制储粮害虫生长,减少储粮过程中粮食损失,实现储粮过程粮食品质一致性,突破当前粮食仓储系统基础理论的研究瓶颈。本文在对平房仓储粮热湿耦合系统水分迁移传递机理研究的国内外研究现状分析的基础上,提出基于多孔介质理论,考虑尺寸效应对于微/纳米多孔结构中导热及流动的影响,从介观和微观尺度下研究其传热传质内在机理和规律,建立宏、微观尺度下粮堆多孔介质多场下的传热传质数学模型,在研究中将粮仓视为整体的生态系统,综合考虑热场、湿度场和气流场,对三者进行耦合分析,从而实现平房仓储粮生态多场耦合系统水分迁移传递的机理探讨,以确保国家粮食安全。最后,给出了具体解决策略和思路。     

ERROR ANALYSIS IN ESTIMATING THERMAL DIFFUSIVITY FROM HEAT PENETRATION DATA1

The ability to predict thermal diffusivity from heat penetration data containing normally distributed errors in can dimensions, measurements in time, measurements of temperature, thermocouple probe location, and assumptions concerning surface heat transfer coefficients was investigated using a nonlinear least squares solution of Fourier's heat conduction equation. Thermal diffusivity calculated from heat penetration data is largely dependent on errors associated with temperature measurement and to a lesser extent dependent on errors in thermocouple probe location. Errors in can dimensions and time measurement had only a minor influence on the prediction of thermal diffusivity. Best prediction accuracy is obtained under the following conditions: (1) When a large can with a length over diameter ratio close to 0.8 is used; (2) when the difference between the initial and heating medium temperature is greater than 40°C; (3) when the data used for calculation of thermal diffusivity is limited to the temperature ratio range of 0.15 to 0.85; (4) when the Biot Numbers for the surfaces of the can are measured or known to be greater than 200; (5) when an accurate time clock is used, and when the position of the thermocouple probe is accurately known.     

3D modelling of coupled mass and heat transfer of a convection-oven roasting process

A 3D mathematical model of coupled heat and mass transfer describing oven roasting of meat has been developed from first principles. The proposed mechanism for the mass transfer of water is modified and based on a critical literature review of the effect of heat on meat. The model equations are based on a conservation of mass and energy, coupled through Darcy's equations of porous media — the water flow is mainly pressure-driven. The developed model together with theoretical and experimental assessments were used to explain the heat and water transport and the effect of the change in microstructure (permeability, water binding capacity and elastic modulus) that occur during the meat roasting process. The developed coupled partial differential equations were solved by using COMSOL Multiphysics®3.5 and state variables are predicted as functions of both position and time. The proposed mechanism was partially validated by experiments in a convection oven where temperatures were measured online.     

Experimental and numerical investigation of heat and mass transfer during drying of Hayward kiwi fruits (Actinidia Deliciosa Planch)

In this paper we undertake an experimental and numerical study on heat and mass transfer analysis during drying of kiwi fruits. In the experimental part, the effects of various drying conditions in terms of air velocity, temperature and relative humidity on drying characteristics of kiwi fruits are investigated. In the numerical part, the external flow and temperature fields are studied using a commercial CFD package. From these fields, the local distributions of the surface convective heat transfer coefficients for the fruits are determined to predict the local convective mass transfer coefficients through the analogy between the thermal and concentration boundary layers (known as the Chilton–Colburn analogy). In addition, the time-dependent temperature and moisture distributions for different cases are obtained using the code developed to investigate heat and mass transfer aspects inside the fruits. Numerical results are then compared with experimental data and a considerably high agreement is obtained.     

Thermophysical Properties of Okara During Drying

The simulation of heat transfer during thermal treatments of foods requires the knowledge of thermophysical properties of the material. In this study some thermophysical properties of okara, such as density, specific heat, thermal conductivity, thermal diffusivity, heat transfer coefficient, and mass transfer coefficient, were obtained during a drying process. Okara was extruded in the shape of spherical pellets and then dried in a fixed bed dryer from 78% of moisture content (w.b.) until 3%. During the drying process, the water content and the temperature of the samples were periodically measured. The thermal properties were obtained from empirical correlations found in the literature, which use the okara centesimal composition, analyzed in a laboratory, and the relative humidity and velocity of the drying air, measured during the process. The results in this study showed that it is possible to estimate the thermal properties cited using the experimental moisture content history and the centesimal composition of the food.     

Theoretical analysis of two hot water cabinet systems for decontamination of sides of beef

The theory underlying the use of hot water to reduce the numbers of microbial contaminants of public health significance on freshly slaughtered animals was investigated. An analysis of steady-state predictions of microbial reductions and accompanying evaporative heat and mass losses in a hot water cabinet for the decontamination of beef sides is developed, based on published correlations. This is more comprehensive than previously undertaken and is used to compare two methods of contacting hot water with the sides of beef: conventional pressure sprays and an alternative, overhead distributor or 'deluge' system. Predictions indicate that a distributor cabinet does not need doors or thermal insulation, and highlight the potential economy and practical advantages over conventional spraying.     

电子烟多口抽吸过程的传热传质数值模拟

为探究电子烟烟液在多孔雾化芯内雾化过程中的传热传质行为, 建立了适用于模拟电子烟多口抽吸使用场景的多口抽吸模型, 并应用MATLAB软件对模型进行求解, 经验证模型具有一定的准确性。利用多口抽吸模型模拟逐口抽吸条件下电子烟烟液相变过程的传热传质特性、烟液成分变化并计算热效率。结果表明:①雾化芯孔隙中的烟液在抽吸间隙发生降温, 在30 s的抽吸间隙内, 烟液温度无法降至环境温度, 随着抽吸口数的增加, 逐口抽吸开始时刻和结束时刻的烟液温度较上一口相比平均提高4.4%;②在模拟的5口抽吸中, 烟液的平均气化速率呈现先增大后减小的趋势, 第2口抽吸时烟液的平均气化速率达到最大值2.80 mg/s;③随着抽吸口序的增大, 逐口的系统升温耗能呈现先减小后增大的趋势, 逐口的烟液气化耗能呈现先增大后减小的趋势, 逐口的导热、对流、辐射3项热损失不断增大, 每一口抽吸的热损失较上一口分别平均提高8.4%、6.8%、11.6%。每口抽吸的热效率随抽吸口数的增加而减小, 当抽吸口数从1口增加至5口, 每口抽吸的热效率从93.3%降至90.9%。      

Microbial Inactivation Kinetics in Soymilk during Continuous Flow High-Pressure Throttling

ABSTRACT:  The thermal resistance of  Clostridium sporogenes  PA 3679 ATCC 7955 was determined in soymilk (pH 7) and 0.1% peptone water (pH 7) by the capillary tube method. In the continuous flow high-pressure throttling, the temperature of soymilk increased due to instantaneous pressure release and the additional heat was supplied by a heat exchanger to achieve the set temperature. The soymilk was immediately cooled after a short preset hold time to below 40 °C. A significant increase in the heat resistance was observed in  C. sporogenes  spores when heated in soymilk in comparison to 0.1% peptone water. The  D ₁₂₁-value for spores in soymilk was approximately 3-folds higher than peptone water. The  z- value was also much higher in soymilk as compared to that in 0.1% peptone water. Continuous flow high-pressure throttling (HPT) from 207 or 276 MPa to atmospheric pressure reduced the microbial populations in inoculated soymilk up to 6 log cycles when the holding times were 10.4, 15.6, and 20.8 s and the process temperatures were 85, 121, 133, and 145 °C, respectively. The sporicidal effect increased as the operating pressure, time, and temperature were increased. More injured spores were found at 207 MPa than at 276 MPa, indicating that lower pressure caused cell injury whereas high pressure caused cell death.