Multiscale Transport in Expanding Biopolymers During Extrusion: Modeling and Experimental Verification

挤出过程中膨胀生物聚合物的多尺度传输：建模和实验验证

• 批准号: 0756762
• 负责人: Pawan Takhar
• 金额: $ 30万
• 依托单位: Texas Tech University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2013-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0756762&HistoricalAwards=false
• 关键词: Multiscale; Transport; Expanding; Biopolymers; During

CBET-0756762TakharA large number of products in food, feed, plastics and biomedical industries are formed by extrusion of starch, which involves forcing it at a high temperature and pressure through a narrow die. Upon exiting the die, the starch expands due to sudden drop in pressure. The expansion causes changes in structural, mechanical and textural characteristics of starch. Controlling the final product characteristics during expansion is a tedious task because of the involvement of multiscale heat and fluid (liquid and vapor) transport processes interacting with the surrounding biopolymeric matrix from micro to macroscale. [Intellectual Merit] In the proposed research, a three-scale predictive modeling tool will be developed using the hybrid mixture theory of porous media. Three-scale laws of conservation of mass, momentum and energy will be used and the second law of thermodynamics will be exploited to develop multiscale fluid and heat transport equations coupled with thermomechanics of expansion. The developed equations will be used for predicting the liquid and vapor transport and thermomechanical changes in the starch matrix during expansion. The solid phase will be modeled as viscoelastic and the liquid phase will be modeled as viscous. The effect of glass transition, which plays a key role in expansion of starches and end-product characteristics, will be investigated. The mathematical model will be solved using numerical simulations. The required experimental parameters are expected to be the liquid and vapor permeabilities, glass transition behavior, thermal diffusivity and viscoelastic properties. Some of these parameters will be obtained from the literature and the remaining will be measured experimentally. Surface temperature and thermal gradients in the starch exiting the die will be recorded using hyperdermic thermocouples. Heat transfer will be accounted by developing a three-scale generalized Laplace equation. Various stages of expansion will be recorded with a digital camcorder. Structural and textural characteristics of expanded starch foam will be measured using porosity measurements, scanning electron microscopy and mechanical testing. The computer program will be made general so that it could also be used for other biopolymers after using different properties. [Broader Impact] The project will train two doctoral students and one undergraduate student. Efforts will be made to recruit these students from women and/or minority groups. A lab exercise will be included in senior/graduate level courses taught by PIs, in which the students will play with the developed computer program with basic understanding of the underlying equations and compare the results with the experimental observations. The lab exercise will be simplified and repeated for minority freshmen, high school students, and women interested in engineering during their visit to Texas Tech and University of Nebraska under various programs in place at these Universities. The project will allow including a new component to Texas Tech's Mentor Tech program designed for minority students. The research outcomes will be disseminated to the scientific community and biopolymer industry through conference presentations and peer-reviewed publications. [Potentially Transformative Nature] The study will contribute significantly for the efficient production of foods, biodegradable plastics and numerous other products for medical and biotechnological applications by extrusion. It will aid the researchers and engineers in these diverse fields to develop novel starch based products using knowledge gained from the computer based predictive tool. This will allow saving time, effort, energy and raw materials due to efficient design and operation of the starch expansion process.

CBET-0756762Takhar 食品、饲料、塑料和生物医学行业的大量产品都是通过淀粉挤压形成的，这涉及到在高温和高压下迫使淀粉通过狭窄的模具。 离开模具后，淀粉由于压力突然下降而膨胀。 膨胀导致淀粉的结构、机械和质地特性发生变化。 在膨胀过程中控制最终产品的特性是一项繁琐的任务，因为涉及从微观到宏观与周围生物聚合物基质相互作用的多尺度热和流体（液体和蒸汽）传输过程。 [智力优点] 在拟议的研究中，将利用多孔介质的混合混合物理论开发三尺度预测建模工具。 将使用质量、动量和能量守恒定律的三尺度定律，并利用热力学第二定律来开发与膨胀热力学相结合的多尺度流体和热传输方程。 所开发的方程将用于预测膨胀过程中淀粉基质的液体和蒸汽传输以及热机械变化。 固相将被建模为粘弹性，液相将被建模为粘性。 将研究玻璃化转变的影响，玻璃化转变在淀粉膨胀和最终产品特性中起着关键作用。数学模型将通过数值模拟来求解。 所需的实验参数预计为液体和蒸汽渗透率、玻璃化转变行为、热扩散率和粘弹性。 其中一些参数将从文献中获得，其余参数将通过实验测量。 使用皮下热电偶记录离开模具的淀粉的表面温度和热梯度。 将通过建立三尺度广义拉普拉斯方程来计算传热。 膨胀的各个阶段将用数码摄像机记录下来。膨胀淀粉泡沫的结构和质地特性将通过孔隙率测量、扫描电子显微镜和机械测试来测量。计算机程序将变得通用，以便在使用不同的特性后也可用于其他生物聚合物。 【更广泛的影响】该项目将培养两名博士生和一名本科生。 我们将努力从女性和/或少数群体中招收这些学生。 PI 教授的高级/研究生课程中将包含实验室练习，学生将在对基本方程有基本了解的情况下使用开发的计算机程序，并将结果与​​实验观察结果进行比较。根据这些大学制定的各种计划，在访问德克萨斯理工大学和内布拉斯加大学期间，将为少数族裔新生、高中生和对工程学感兴趣的女性简化并重复实验室练习。 该项目将在德克萨斯理工大学为少数族裔学生设计的 Mentor Tech 项目中纳入一个新的组成部分。 研究成果将通过会议演讲和同行评审出版物向科学界和生物聚合物行业传播。 [潜在的变革性] 该研究将为通过挤压高效生产食品、可生物降解塑料和许多其他用于医疗和生物技术应用的产品做出重大贡献。 它将帮助这些不同领域的研究人员和工程师利用从计算机预测工具中获得的知识来开发新型淀粉基产品。 由于淀粉膨胀工艺的高效设计和操作，这将节省时间、精力、能源和原材料。