###### Abstract  
An efficient and reliable spacecraft payload thermal management method is one of the key problems to build China Space Station (CSS). Aiming at the outstanding characteristics and difficulties of the payloads rack in the experimental lab module of CSS, in the aspects of thermal control interface, boundary constraint, scale quantity, space layout, diversity of temperature control, operation mode and working life, etc., a two-stage thermal management scheme based on single-phase fluid loop is proposed and constructed. A fluid drive unit is designed to drive the fluid circulation and health management of the module thermal control bus (TCB). In view of the different characteristics of the payload racks, three different types of second-stage thermal control systems are proposed, and different thermal control terminals are designed, in order to solve the problem of thermal control resource allocation and health management in payload racks. A method based on \"pump bypass\" and \"valve resistance ratio\" is used to control the flow rate of the thermal management system. Based on the overall scheme of the thermal management system and the developed flight products, on-orbit verification and data analysis are carried out. Flight verification shows that the key parameters of the fluid loop in the thermal management system on orbit are basically consistent with the ground data; the maximum deviation is 1.84%. The pressure control accuracy of the bypass system reaches \(\pm\)2%, and the active heat transfer efficiency of the integrated thermal management system is over 83%, which can effectively meet the thermal control requirements of the two-stage payloads in the module and rack. After on-orbit flight verification, the designed thermal control system works well on orbit and exhibits good stability. China space station; payload; thermal management system; thermal control bus; single-phase fluid loop; on-orbit data +
Footnote †: journal: Applied sciences  
As the need to explore space continues to grow, the load scale and temperature control requirements of large spacecraft, such as target spacecraft, space laboratories, space stations and moon and deep space probes, have reached unprecedented levels [5; 6; 7]. The traditional thermal control methods cannot meet the work needs of spacecraft, and a new active thermal control system based on the concept of thermal management is proposed. Because of the strong ability regarding adjustment and adaptation, high efficiency of heat transfer, high precision of temperature control and strong ability of upgrade and expansion, it has become the main method of thermal control for large spacecraft in the world. New thermal control technologies such as single-phase fluid loop driven by pump, two-phase fluid loop, convective ventilation, space heat pump and consumable heat sink, etc., provide the technical basis for the integrated thermal control of complex large spacecraft [8; 9]. Different types of thermal management systems have been developed in conjunction with the construction of large spacecraft [10]. Since the 1990s, the International Space Station (ISS) has been built on orbit for more than 20 years by countries including the United States, Europe, Japan, Russia, Italy, etc. [11]. A total of 33 payload racks were installed in the four experimental modules of the ISS. According to the load characteristics and requirements of different modules, an integrated heat management system with single-phase fluid loop and different configurations is constructed [12]. Due to the lack of consideration of global load characteristics and working mode in the early stage of construction, the thermal control system of some modules has some limitations in the practical application on orbit [13]. \"Destiny\" used a medium-low temperature double fluid loop to adjust the load and heat, and a closed-loop method was used to adjust the temperature and flow rate outside the rack dynamically.