EPRI: Spray-Freezing of Phase-Change Materials for Decoupled Condensation and Heat Rejection in Next Generation Air-Cooled Power Plants

1357918 SunThermal用于蒸汽发电厂的管理系统约占美国淡水抽取总量的40%。由于全球淡水资源的减少，这些系统的持续运行构成了重大的工程挑战。因此，该项目旨在开发变革性的“干式冷却”技术，完全消除现代发电厂中冷却蒸汽冷凝器的水的使用。这将通过相变材料（PCM）的空气冷却喷雾冷冻来实现。在蒸汽侧，浆料浴中的固体PCM颗粒将使蒸汽冷凝温度锚为恒定的低值，而与环境空气条件无关。在空气侧，与当前的空气冷却冷凝器（ACC）相比，毫米尺寸的PCM液滴的喷雾冷冻将显著增加表面积以及传热系数。这种方法简化了冷凝和排热过程，显著降低了蒸汽冷凝温度、压降和系统尺寸。此外，拟议的喷雾冷冻热能存储概念还将为其他高负载冷却和加热应用提供高容量，快速充电/放电存储解决方案，包括建筑HVAC和数据中心。德雷克塞尔大学、先进冷却技术公司（ACT）和WorleyParsons（WP）之间的合作将有助于弥合基础研究和商业化颠覆性技术开发之间的差距。研究生和本科生都将受益于ACT和WP的研究合作和实习机会。该项目利用相变材料（PCM）的喷雾冷冻来解耦新型空冷冷凝器开发中的蒸汽冷凝和排热。喷雾冷冻技术广泛应用于食品工业中，这是由于在高表面积与体积比的液滴中可实现快速冷却速率。在所提出的系统中，热量从冷凝器蒸汽传递到由悬浮在液化PCM中的固体PCM颗粒组成的浆料浴。然后将液体PCM从浴中抽出并喷入冷却塔中，在冷却塔中将热量排出到环境空气中。PCM液滴在它们被对流冷却时固化，并落回PCM浆料浴中完成循环。整合的大学-工业团队将结合联合收割机专家在相变材料，复杂流体，两相流，空气冷却热交换器，调查两个基本的科学原理，以及克服技术挑战，在实现和最终实施这一新颖的喷雾冷冻冷凝器的概念。大学与工业界合作的具体任务是：（i）开发具有高导热性和最佳喷雾/喷射特性的新型相变材料;（ii）研究喷嘴设计和操作对液滴喷雾和冻结的影响;（iii）表征相变材料浆料在蒸汽管组上同时熔化和流动的特性;（iii）研究相变材料浆料在蒸汽管组上同时熔化和流动的特性。㈣设计、制造、并表征实验室规模的组件和子规模的概念验证喷雾-这些任务将通过综合研究方法来实现，包括先进的建模和直接实验表征相变材料的热流体特性，复杂的流体流动和对流传热。

1357918SunThermal management systems for steam-driven electric power plants account for approximately 40% of total fresh water withdrawals in the US. Due to dwindling access to fresh water resources worldwide, continued operation of these systems poses a significant engineering challenge. As such, this project aims to develop transformative "dry-cooling" technologies completely eliminating the use of water for cooling steam condensers in modern electric power plants. This will be achieved using air-cooled spray-freezing of phase-change materials (PCM). On the steam side, solid PCM particles in a slurry bath will anchor the steam condensation temperature to a constant, low value regardless of ambient air conditions. On the air side, spray freezing of millimeter-sized PCM droplets will dramatically increase surface area, as well as heat transfer coefficient, as compared to current air-cooled condensers (ACCs). This approach decouples the condensation and heat rejection processes, significantly reducing steam condensation temperature, pressure drop, and system size. Additionally, the proposed spray-freezing thermal energy storage concept will also provide high capacity, fast charging/discharging storage solutions for other high-load cooling and heating applications, including building HVAC and data centers. The collaboration between Drexel University, Advanced Cooling Technologies (ACT), and WorleyParsons (WP), will help to bridge the gap between fundamental research and disruptive technology developments for commercialization. Both graduate and undergraduate students will benefit from research co-ops and internship opportunities at ACT and WP. This project leverages the spray-freezing of phase-change materials (PCMs) to decouple steam condensation and heat rejection in the development of novel air-cooled condensers. Spray freezing techniques are widely used in the food industry, due to the fast cooling rates achievable in high surface-to-volume ratio droplets. In the proposed system, heat is transferred from the condenser steam to a slurry bath comprised of solid PCM particles suspended in liquefied PCM. The liquid PCM is then drawn from the bath and sprayed into a cooling tower, where the heat is rejected to the ambient air. The PCM droplets solidify as they are convectively cooled, and fall back to the PCM slurry bath completing the cycle. The integrated university-industry team will combine experts in phase change materials, complex fluids, two-phase flow, and air-cooled heat exchangers to investigate both fundamental scientific principles as well as overcome technical challenges in the realization and eventual implementation of this novel spray-freezing condenser concept. The specific tasks of the university-industry collaboration are to:(i) Develop novel PCMs with high thermal conductivity and optimal spray/jetting characteristics;(ii) Investigate the effects of nozzle design and operation on spraying and freezing of droplets;(iii) Characterize the simultaneous melting and flowing of PCM slurries over banks of steam tubes;(iv) Design, fabricate, and characterize lab-scale components and sub-scale proof-of-concept spray-freezing condenser systems.These tasks will be achieved through an integrated research methodology including advanced modeling and direct experimental characterizations of thermofluidic properties of PCMs, complex fluid flows, and convective heat transfer.