Faghiri Shahin, Poureslami Parham, Partovi Aria Hadi, Shafii Mohammad Behshad
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran.
School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran.
Sci Rep. 2023 Jun 29;13(1):10543. doi: 10.1038/s41598-023-37712-x.
Embracing an interaction between the phase change material (PCM) and the droplets of a heat transfer fluid, the direct contact (DC) method suggests a cutting-edge solution for expediting the phase change rates of PCMs in thermal energy storage (TES) units. In the direct contact TES configuration, when impacting the molten PCM pool, droplets evaporate, provoking the formation of a solidified PCM area (A). Then, they reduce the created solid temperature, leading to a minimum temperature value (T). As a novelty, this research intends to maximize A and minimize T since augmenting A expedites the discharge rate, and by lowering T, the generated solid is preserved longer, resulting in a higher storage efficacy. To take the influences of interaction between droplets into account, the simultaneous impingement of two ethanol droplets on a molten paraffin wax is surveyed. Impact parameters (Weber number, impact spacing, and the pool temperature) govern the objective functions (A and T). Initially, through high-speed and IR thermal imaging, the experimental values of objective functions are achieved for a wide range of impact parameters. Afterward, exploiting an artificial neural network (ANN), two models are fitted to A and T, respectively. Subsequently, the models are provided for the NSGA-II algorithm to implement multi-objective optimization (MOO). Eventually, utilizing two different final decision-making (FDM) approaches (LINMAP and TOPSIS), optimized impact parameters are attained from the Pareto front. Regarding the results, the optimum amount of Weber number, impact spacing, and pool temperature accomplished by LINMAP and TOPSIS procedures are 309.44, 2.84 mm, 66.89 °C, and 294.98, 2.78 mm, 66.89 °C, respectively. This is the first investigation delving into the optimization of multiple droplet impacts for TES applications.
直接接触（DC）方法通过利用相变材料（PCM）与传热流体液滴之间的相互作用，为加快热能存储（TES）单元中PCM的相变速率提供了一种前沿解决方案。在直接接触式TES配置中，液滴撞击熔融的PCM池时会蒸发，促使形成固化的PCM区域（A）。然后，它们降低所形成固体的温度，导致最低温度值（T）。本研究的新颖之处在于，由于增大A可加快放电速率，而降低T能使生成的固体保存更长时间，从而提高存储效率，因此旨在最大化A并最小化T。为了考虑液滴之间相互作用的影响，研究了两个乙醇液滴同时撞击熔融石蜡的情况。冲击参数（韦伯数、冲击间距和池温）控制目标函数（A和T）。首先，通过高速和红外热成像，在广泛的冲击参数范围内获得目标函数的实验值。随后，利用人工神经网络（ANN）分别对A和T拟合了两个模型。接着，将这些模型提供给NSGA-II算法以进行多目标优化（MOO）。最后，利用两种不同的最终决策（FDM）方法（LINMAP和TOPSIS），从帕累托前沿获得优化的冲击参数。结果表明，LINMAP和TOPSIS程序实现的韦伯数、冲击间距和池温的最佳值分别为309.44、2.84毫米、66.89°C和294.98、2.78毫米、66.89°C。这是首次深入研究用于TES应用的多液滴冲击优化的研究。
