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

在区域供热/制冷系统中，形成蠕虫状胶束(WLM)的表面活性剂流体被用作减阻剂(DR)。直冷式空调是一种高效的房屋和建筑物供暖和制冷方式，在世界各地正变得越来越受欢迎。DR试剂减少了湍流中的摩擦损失，因此有助于节省高达50%的抽水能量成本。然而，基于WLM的流体在DHS中的一个关键问题是它们也降低了换热器中的换热速率(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性或光流变(PR)表面活性剂来克服上述问题。其概念是在流体进入热交换器之前使用紫外光关闭WLM(将其转化为球形胶束)，然后在流体离开热交换器后重新打开WLMS。通过这种方式，研究人员希望在管流中获得有效的HT率和有效的DR的组合。该项目的PI是减阻方面的专家，尤其是使用表面活性剂流体。Co-PI最近设计了一种使用简单、廉价的表面活性剂和反离子的新型PR液。在一起，PI带来了一种新的、潜在的变革性的方法来解决旧问题。智力价值：在DR应用中使用PR液的概念是一种高风险、高回报的探索性方法，如果它能被证明有效，可能会转化为重大突破。本项目是一项为期一年的试验性研究，以证明原则。当PR流体含有WLMS时，它有望提供出色的减阻；当微观结构切换到更小的球形胶束时，它应该提供高效的、类似水的热传输率。我们意识到这一项目所涉及的挑战，特别是需要在短时间窗口内迅速转换结构。解决这些挑战的办法是综合运用工程学原理和物理化学/有机化学。研究人员将修改PR液的配方，以便快速完成组成有机反离子的光异构化。更广泛的影响：使用PR液可能节省的总能源将使它们非常适合用于DHC系统。如果该项目成功，我们将提请DHC领域注意这项工作，例如，通过在国际区域供热和制冷协会的会议上发表演讲，来自世界各地的DHC工程师聚集在一起，交流新的技术想法。国际和平协会在这一领域有很长的工作历史，并在国家科学基金会的支持下组织了会议和研讨会。该项目还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都有很好的记录，包括那些来自代表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.