Starting and running performance of a pulsating heat pipe with micro encapsulated phase change material suspension

Pulsating heat pipe (PHP) is an efficient heat transfer technology. The micro encapsulated phase change material (MEPCM) suspension is a novel latent heat fluid with high heat storage density. The research on the PHP with MEPCM suspension is of great significance for expanding the types of working fluids and studying the operating performance. An experimental investigation of starting and running performance was carried out on a closed loop PHP with MEPCM suspension at mass concentration of 0.5%. The results show that the PHP charged with MEPCM suspension starts unstably with irregular oscillating under lower heating power of 30-90 W, while it runs stably after starting with heating power increasing to 120 W. The start-up time of PHP charged with MEPCM suspension first drops rapidly, then flattens from 50 s to 20 s with increasing heating power and it still maintains at 20 s with the increasing of heating power from 150 W during experiments, which indicates the influence on the start-up time from further increasing heating power becomes smaller on the condition that the heating power increases to a certain level. Compared with 70% of filling ratio, conditions with 35% and 50% of that showed better performance. Gravity is very important to overcome the viscous resistance of working fluids. The running performance of PHP was slightly affected by inclination angle which was greater than 60 degrees. When it dropped to 30 degrees, the running deteriorated obviously. However, the PHP with 35% of filling ratio couldn't run normally at a small inclination angle of 30 degrees

Influence of Cooling Water Flow Rate on Start and Heat Transfer Performance of Pulsating Heat Pipe at Different Inclination Angles

Pulsating heat pipe (PHP) is an efficient heat transfer technology applied in the fields of heat dissipation and energy utilization. There are many factors affecting the heat transfer of PHP, including working fluid, filling ratio, inclination angle, etc. The cooling capacity of the cooling water system at the condensing section to the working fluid is also an important factor affecting the starting and operating of PHP. The research on PHP at different cooling water flow rates is of great significance for enhancing the operating performance. An experimental investigation of starting and running performance is carried out on a closed loop PHP with ultrapure water under different inclination angles of 90°, 60° and 30°. The starting and heat transfer performance of PHP with a filling ratio of 50% is obtained by adjusting the heat input in the range of 30–210 W at different cooling water flow rates of 6.7 g/s, 9.7 g/s and 13.9 g/s. The temperature and heat transfer resistance are used for analyzing the heat transfer performance. The results show that the starting mode, initial pulsating temperature and different heat transfer effects are brought about by different cooling water flow rates. It is observed that the cooling water flow rate has no obvious influence on the starting mode of PHP and that the starting mode of PHP is temperature progressive, starting with the increase in cooling water flow rates at a heating input of about 30 W. The influence of cooling water flow rates on the heat transfer performance of PHP is affected in a different way by inclination angles. The heat transfer performance of PHP with an inclination angle of 90° is similar at 6.7 g/s, 9.7 g/s and 13.9 g/s but, under the condition of 60° and 30°, the heat transfer resistance drops within a certain range effectively with an increasing cooling water flow rate from 6.7 g/s to 9.7 g/s and the heat transfer performance does not change significantly with the cooling water flow rate increasing to 13.9 g/s. Thus, there is an optimal value for the cooling water flow rate during the operating of PHP. The inclination angle also has an important effect on the temperature pulsating, and the temperature of PHP affected by gravity is stable with an inclination angle of 90°. However, the reduced influence of gravity on the backflow of the working fluid drops when the inclination angle decreases from 90° to 30°, and the wall temperature increases due to local overheating when the high heat input occurs

A Data-Driven Approach to Identify Major Air Pollutants in Shanghai Port Area and Their Contributing Factors

Air pollution is a growing concern in metropolitan areas worldwide, and Shanghai, as one of the world’s busiest ports, faces significant challenges in local air pollution control. Assessing the contribution of a specific port to air pollution is essential for effective environmental management and public health improvement, making the analysis of air pollution contributions at a selected port in Shanghai a pertinent research focus. This study aims to delve into the distribution patterns of atmospheric pollutants in port areas and their influencing factors, utilizing a data-driven approach to unveil the relationship between pollution sources and dispersion. Through a comparative analysis of pollution levels in the port’s interior, surrounding regions, and urban area concentrations, we ascertain that carbon monoxide (CO) and nitric oxide (NO) are the primary pollutants in the port, with concentrations significantly exceeding those of the surrounding areas and urban area levels. These two pollutants exhibit an hourly pattern, with lower levels during the day and higher concentrations at night. Employing a random forest model, this study quantitatively analyzes the contribution rates of different factors to pollutant concentrations. The results indicate that NO concentration is primarily influenced by operational intensity and wind speed, while CO concentration is mainly affected by meteorological factors. Further, an orthogonal experiment reveals that maintaining daily operational vehicle numbers within 5000 effectively controls NO pollution, especially at low wind speeds. Additionally, humidity and temperature exhibit similar trends in influencing NO and CO, with heightened pollution occurring within the range of 75% to 90% humidity and 6 °C to 10 °C temperature. Severe pollution accumulates under stagnant wind conditions with wind speeds below 0.2 m/s. The results help to explore the underlying mechanisms of port pollution further and use machine learning for early pollution prediction, aiding timely warnings and emission reduction strategy formulation