Behaviours of droplets interaction with solid surfaces and thermal performance of a pulsating heat pipe
Publication Date
July 21, 2023
Creator
Abstract
Over the past few decades, liquid drops and droplets are the ubiquitous in nature๏ผ which have attracted many investigationsโ attention. Droplets interaction with solid surface plays a crucial role in many industrial applications, such as inkjet printing, spraying cooling, biosensors, DNA microarrays, Nanotechnology, and so on. However, the behaviours of droplets interaction with solid surfaces are unexpected, resulting in adverse or beneficial effects for these applications. Therefore, a large amount of literature focuses on exploring the mechanism behind this phenomenon and finding effective strategies to control it. This study aims to explore how to control the distribution of deposition patterns with various strategies and advance the understanding of the droplet impact behaviours on the surface with different roughness and substrate morphology. In this dissertation, the study of the behaviours of droplets interaction with solid surfaces is divided into two parts. Firstly, the evaporation process and deposition patterns of a saline droplet on a copper substrate have been experimentally studied by adjusting the surface roughness and substrate temperature. The experimental results show that the coffee ring effect is suppressed by increasing substrate roughness, and the deposited patterns transit from uniformity, ring-like structure to dual ring patterns with substrate temperature increasing. Secondly, the dynamic behaviours of droplet impact on a conical structure with different cone angles and surface roughness have been experimentally investigated with the help of a high-speed camera. The experimental results show that the maximum spreading factor ๐ฝ๐๐๐ฅ increases as the Weber number increases and the increase in the surface roughness and cone angle reduces the ๐ฝ๐๐๐ฅ . In addition, the splashing can be promoted by increased the surface roughness and cone angle, which is characterized by critical Weber number ๐๐๐๐.
The investigation of the thermal performance of a closed loop pulsating heat pipe(CLPHP) is also conducted. Nowadays, the energy crisis and serious environmental pollution are threatening people all over the world. Efficient energy management is one of the feasible methods to solve the existing energy crisis and has attracted extensive attention. Pulsating heat pipe (PHP), as a potential thermal management system, has great potential in application due to its simple structure, low cost and excellent heat transfer performance. The thermal performance of the PHP is affected by many factors. Although there are many investigations are carried out to understand the effects of various factors on the thermal performance of the PHP, the optimal conditions have not been found. This section devotes to experimentally explore the strategy of enhancing the thermal performance of PHPs and further reveal the working mechanism of PHPs. The experiments are conducted using a glass PHP with micro encapsulated phase change material suspension(MEPCMS). The micro encapsulated phase change material suspension(MEPCMS) is selected for the working fluids containing microencapsulated phase change materials. The results show that the thermal performance of PHP can be enhanced by applying the MEPCMS working fluid dependent on the filling ratio and concentration of the working fluid. Increasing the filling ratio not only improves the maximum heat transfer capacity of PHP but also enhances the requirement of driving force which limits the thermal performance of the PHP. With the increasing concentration of working fluid, the heat transfer capacity also can be enhanced while increasing the viscosity of the working fluid which hinders the motion of the working fluid. Therefore, the influence of filling ratio and concentration on the PHP should consider the combined effect of passive effect and negative effect of them. The best thermal performance is 0.37ยฐC/W when the filling ratio, input power, and concentration of the MEPCMS are 40%, 90W, and 4wt% in this study.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
Department of Architecture and Built Environment (UK)
eprints ID
73194
UoN Repository URI
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