Investigating the Use of Light-Responsive Surfactant Fluids in Turbulent Drag Reduction

在区域供热/供冷系统（dhc）中，可形成虫状胶束（wlm）的消阻剂（DR）被用作减阻剂。DHCs是一种为房屋和建筑物供暖和制冷的有效方式，在世界各地越来越受欢迎。DR剂减少了湍流中的摩擦损失，从而有助于节省高达50%的dhc泵送能源成本。然而，在dhc中使用基于wlm的流体的一个关键问题是，它们也降低了换热器中的传热速率（HT）。这抵消了减阻的有益效果。在这个项目中，研究人员试图通过使用一类光响应或光流变（PR）表面活性剂流体来克服上述问题。这个概念是在流体进入热交换器之前使用紫外线关闭wlm（将它们转换成球形胶束），然后在流体离开热交换器后重新打开wlm。通过这种方式，研究人员希望在管道流动中获得高效高温速率和高效DR的组合。该项目的PI是减阻方面的专家，特别是表面活性剂流体。co-PI最近设计了一种新型的PR流体，使用简单、廉价的表面活性剂和反离子。两党联合起来，为一个老问题带来了一种全新的、可能具有变革性的方法。知识优势：在DR应用中使用PR流体的概念是一种高风险、高回报的探索性方法，如果能够证明有效，可能会转化为重大突破。目前的项目是一项为期一年的试点研究，以证明其原理。当PR液中含有WLMs时，它有望提供出色的减阻效果；当微观结构切换到更小的球形胶束时，它应该提供有效的，像水一样的传热速率。我们意识到这个项目所涉及的挑战，特别是需要在短时间内快速切换结构。解决这些挑战的方法是结合工程原理和物理/有机化学。研究人员将修改PR流体的配方，使组成有机反离子的光异构化迅速完成。更广泛的影响：使用PR流体的潜在总能源节约将使其在DHC系统中非常有吸引力。如果这个项目成功，我们将把这项工作引起DHC领域的注意，例如，在国际区域供热和制冷协会的会议上做报告，来自世界各地的DHC工程师聚集在一起交流新的技术思想。PI在这一领域有着悠久的工作历史，并在NSF的支持下组织了会议和研讨会。这个项目也将有助于研究生和本科生的教育。PI和co PI在让本科生参与他们的研究方面有着良好的记录，包括那些来自代表性不足的少数群体的学生。

0933295ZakinSurfactant fluids that form wormlike micelles (WLMs) are used as drag reducing (DR) agents in district heating/ cooling systems (DHCs). DHCs are an efficient way to heat and cool homes and buildings and are becoming increasingly popular around the world. DR agents reduce the friction losses in turbulent flow and thereby help to conserve up to 50% of the pumping energy costs in DHCs. However, a key problem with WLM-based fluids in DHCs is that they also reduce the rates for heat transfer (HT) in heat exchangers. This cancels the beneficial effects of drag reduction. In this project, the investigators seek to overcome the above problem by using a class of light responsive or photorheological (PR) surfactant fluids. The concept is to switch off the WLMs (convert them into spherical micelles) using UV light just before the fluid enters the heat exchanger, and thereafter switch the WLMs back on once the fluid exits the heat exchanger. This way, the investigators hope to obtain a combination of efficient HT rates as well as efficient DR in pipe flow. The PI on this project is an expert on drag reduction, especially with surfactant fluids. The co-PI has recently devised a new class of PR fluids using simple, inexpensive surfactants and counterions. Together, the PIs bring a fresh, potentially transformative, approach to an old problem. Intellectual Merit: The concept of using PR fluids in DR applications is a high risk, high reward exploratory approach that could translate into a substantial breakthrough if it can be shown to work. The present project is a pilot study over one year to demonstrate proof of principle. When the PR fluid contains WLMs, it is expected to give excellent drag reduction; when the microstructure is switched to much smaller spherical micelles, it should give efficient, water like heat transfer rates. We are aware of the challenges involved in this project, in particular, the need to rapidly switch the structure in a short time window. The solutions to these challenges are to utilize a combination of engineering principles as well as physical/organic chemistry. The investigators will modify the formulation of the PR fluids so that the photoisomerization of the constituent organic counterions is accomplished rapidly. Broader Impact: The potential total energy savings with the use of PR fluids would make them very attractive for use in DHC systems. If this project is successful, we will bring this work to the attention of the DHC field, e.g., by presentations at meetings of the International District Heating and Cooling Association where DHC engineers from around the world meet to exchange new technical ideas. The PI has a long history of working with this field and has organized meetings and workshops with NSF support. This project will also contribute to the education of graduate and undergraduate students. Both the PI and co PI have a strong track record of involving undergraduate students in their research, including those from under represented minority groups.