A critical review on the thermal management of data center for local hotspot elimination

[Display omitted] •Definition and indicators of the local hotspots are clarified.•The main problems of weak airflow distribution are deeply analyzed.•Thermal management technologies are summarized by different scales for guidance.•Current limitations and future trend of hotspots elimination methods are discussed. The data centers consume a significant amount of energy, with cooling demand accounting for roughly 40% of the total energy usage. The primary reason for this is the presence of the local hotspots. To eliminate these hotspots, the standard approach is to lower the set point temperature of the whole computer room air conditioner (CRAC), resulting in overcooling and energy waste. This study provides an overview of the recent research on local hotspot management strategies, with a focus on the overheated servers as the most likely location of hotspots. To quantify the hotspots, this study provides a clear definition and summarizes the indicators from different aspects. It analyzes the correlation between the inlet and outlet air temperature and the overheating issues, which is often caused by high server loads or poor airflow distribution. And the most fundamental manifestation of the hotspots is hot air recirculation. This study analyzes potential solutions, such as optimizing airflow distribution and shortening the cold airflow path through design, control, and application. Additionally, the study discusses the limitations of the recent hotspots elimination research and proposes future perspectives. The aim of this review is to provide helpful knowledge on local hotspot elimination in the data centers, with consideration for integrated thermal and airflow distribution management strategies. The conclusion may assist in designing, operating, and retrofitting energy-efficient data centers in practice.