## 1 Introduction  
With the rapid development of the Internet, the new generation of information technology, represented by big data, cloud computing, artificial intelligence and block chain, is accelerating the global intelligent transformation and promoting the substantial growth of data centers. According to a report issued by the Ministry of Industry and Information Technology in 2016, the market size of data centers in China has reached 71.45 billion yuan, and the power consumption of data centers accounts for 1.5% of the total power consumption of the whole society [1], and the power consumption of global data centers has also reached 1.1%-1.5% [2]. By 2020, data centers are expected to continue to grow [3],and energy consumption is expected to increase along with demand. At the same time, reducing the energy consumption of high-heat density buildings in data centers has become a research hotspot. To reduce the energy consumption of high thermal density buildings, it is necessary to solve the heat dissipation of data center racks. At present, the data center usually adopts the method of separating the cold and hot channels to solve the problem of high thermal density. However, with the continuous increase of the heating density of the single frame, the high-temperature air outlet of the cabinet is easy to diffuse to the top of the frame, forming a short circuit of cold and hot air. When the method of isolating the cold and hot channels is adopted, the mixing of cold and hot air still exists. It has become a research point to improve the performance of the rack heat exchanger by adopting micro-channel structure heat pipes. Micro-channel heat pipe heat exchangers have the advantages of both heat pipe and micro-channel structure, high heat transfer capacity, long transmission distance, simple processing technology. [PERSON] [4] applied the separated heat pipe to the air conditioning system of the data center, introduced the application principle and working characteristics of the separated heat pipe in the air conditioning system of the data room, and analyzed its research status. [PERSON] [5] studied this based on the gravity of the micro-channel flow boiling type start-up characteristics and heat transfer characteristics of the separated type heat pipe system, the experiment compared the two different channel lengths of aluminum micro-channel evaporator. The experimental results showed that in the circulation of the separated type heat pipe, micro-channel kernel boiling the bubble detachment diameter and the bubble frequency was the single value function of heat flux. [PERSON] [6] comprehensively considered the influence of the inclination angle on heat transfer characteristics, flow characteristics, wear and ash accumulation characteristics in the evaporation section of the separated heat pipe exchanger, and determined the optimal design range of the inclination angle in the evaporation section was 7\({}^{\circ}\)-15\({}^{\circ}\). [PERSON] [7] took CO\({}_{2}\) as the refrigerant to study the influence of the liquid filling rate and the temperature difference between indoor and outdoor on the heat exchange and energy efficiency ratio of the system. The research showed that under the optimal liquid filling rate, with the increase of the temperature difference between indoor and outdoor, the heat exchange and energy efficiency ratio also gradually increased. [PERSON] [8] used the micro-channel heat exchanger as the evaporator of the separated heat pipe, and compared it with the finned tube evaporator. The research showed that under the condition of equal heat exchange, the charging amount of the working medium in the micro-channel evaporator system decreased by 51.9%, while the system EER increased by 2.8%.