# A Review of Pool-Boiling Processes Based on Bubble-Dynamics Parameters
## 1 Introduction  
In the context of ongoing industrialization and informatization, electronic devices have become increasingly miniaturized and highly integrated, especially in sectors such as automotive engineering, artificial intelligence, and data centers [1, 2]. As a consequence, the heat-dissipation challenges from these advancements have become severe. The heat flux of individual chips could reach 100-1000 W/cm\({}^{2}\), which exceeds the cooling performance of traditional air-cooling techniques [3, 4, 5]. Therefore, the boiling cooling, which provides excellent heat-transfer efficiency and uniform temperature distribution, has attracted considerable attention. boiling could transfer heat rapidly and control the wall temperature effectively. Currently, the heat-dissipation capacity of boiling cooling achieves as high as 202 W/cm\({}^{2}\), which is about six times higher than that of conventional air-cooling methods [6]. Therefore, boiling-cooling technology is widely used in various fields, such as nuclear power plants [7], air-conditioning units [8], heat pipes [9], rocket engines [10], battery cooling [11], and electronics cooling [12, 13]. Boiling can be divided into two main categories: pool boiling (e.g., two-phase immersion cooling) and flow boiling (e.g., two-phase minichannel cold plate). Pool boiling, as a passive method of heat transfer through phase change, relies solely on the buoyancy to facilitate the cooling process. This characteristic not only gives pool boiling a high heat-transfer efficiency, but also provides it with several advantageous features. First,it requires minimal maintenance due to its self-sustaining nature. Second, pool boiling eliminates the need for pump induction, resulting in simplified system design and lower energy consumption. Third, the packaging and implementation of pool-boiling systems are relatively easy, making the deployment suitable for various applications. These features allow for a remarkable reduction in energy consumption, making it widely adopted in various industries [14]. In the process of realizing temperature control with pool boiling, the heat-transfer capacity is largely determined by the amount of bubbles generated and transferred. Thus, understanding the mechanism of bubbles formation, growth and detachment is crucial for enhancing heat transfer. In the process of pool boiling, the bubbles will follow a cycle of nucleation, growth, detachment, and nucleation again, as shown in Figure 1. After the bubbles detach from the heated surface during pool boiling, the region will be temporarily devoid of areas for new bubbles. During the early stage of boiling, when the heated wall surface meets the superheating criteria, nucleation sites are formed at the concave pits and the cracks on the wall, inducing bubble nucleation. Then bubbles grow through the combined effects of the thermal boundary layer, micro-convection, and the micro-liquid layer. In this process, the bubbles are mainly subject to the surface tension \(F_{s}\), the liquid static pressure \(F_{p}\) and the excess vapor pressure \(F_{m}\), and the role of gravitational force is usually negligible. When the bubble detachment force exceeds the force dragging the bubble, the bubble detaches from heated surfaces. The superheated wall continues to undergo convective heat transfer with the liquid until the nucleation conditions are met again and the bubble cycle is repeated. Evaluation of the correlations of pool boiling showed that the key factors determining the boiling-heat-transfer process include the nucleation site's density \(N_{s}\), growth rate, detachment diameter \(D_{d}\) and detachment frequency \(f\). Among them, \(N_{s}\) is related to the surface conditions and temperature field, the bubble growth rate is closely related to the force-balance model, and the bubble detachment frequency \(f\) is determined by the growth time \(t_{g}\) and the waiting time \(t_{w}\).